Spec.format: conditional format strings

* veccore: new variants umesimd and vc

* veccore: remove variant umesimd again

bin/spack.bat

@@ -51,65 +51,43 @@ setlocal enabledelayedexpansion
 :: subcommands will never start with '-'
 :: everything after the subcommand is an arg
 
-:: we cannot allow batch "for" loop to directly process CL args
-:: a number of batch reserved characters are commonly passed to
-:: spack and allowing batch's "for" method to process the raw inputs
-:: results in a large number of formatting issues
-:: instead, treat the entire CLI as one string
-:: and split by space manually
-:: capture cl args in variable named cl_args
-set cl_args=%*
+
 :process_cl_args
-rem  tokens=1* returns the first processed token produced
-rem  by tokenizing the input string cl_args on spaces into
-rem  the named variable %%g
-rem  While this make look like a for loop, it only
-rem  executes a single time for each of the cl args
-rem  the actual iterative loop is performed by the
-rem  goto process_cl_args stanza
-rem  we are simply leveraging the "for" method's string
-rem  tokenization
-for /f "tokens=1*" %%g in ("%cl_args%") do (
-    set t=%%~g
-    rem  remainder of string is composed into %%h
-    rem  these are the cl args yet to be processed
-    rem  assign cl_args var to only the args to be processed
-    rem  effectively discarding the current arg %%g
-    rem  this will be nul when we have no further tokens to process
-    set cl_args=%%h
-    rem  process the first space delineated cl arg
-    rem  of this iteration
-    if "!t:~0,1!" == "-" (
-        if defined _sp_subcommand (
-            rem  We already have a subcommand, processing args now
-            if not defined _sp_args (
-                set "_sp_args=!t!"
-            ) else (
-                set "_sp_args=!_sp_args! !t!"
-            )
-        ) else (
-            if not defined _sp_flags (
-                set "_sp_flags=!t!"
-                shift
-            ) else (
-                set "_sp_flags=!_sp_flags! !t!"
-                shift
-            )
-        )
-    ) else if not defined _sp_subcommand (
-        set "_sp_subcommand=!t!"
-        shift
-    ) else (
+rem Set first cl argument (denoted by %1) to be processed
+set t=%1
+rem shift moves all cl positional arguments left by one
+rem meaning %2 is now %1, this allows us to iterate over each
+rem argument
+shift
+rem assign next "first" cl argument to cl_args, will be null when
+rem there are now further arguments to process
+set cl_args=%1
+if "!t:~0,1!" == "-" (
+    if defined _sp_subcommand (
+        rem  We already have a subcommand, processing args now
         if not defined _sp_args (
             set "_sp_args=!t!"
-            shift
         ) else (
             set "_sp_args=!_sp_args! !t!"
-            shift
+        )
+    ) else (
+        if not defined _sp_flags (
+            set "_sp_flags=!t!"
+        ) else (
+            set "_sp_flags=!_sp_flags! !t!"
         )
     )
+) else if not defined _sp_subcommand (
+    set "_sp_subcommand=!t!"
+) else (
+    if not defined _sp_args (
+        set "_sp_args=!t!"
+    ) else (
+        set "_sp_args=!_sp_args! !t!"
+    )
 )
-rem  if this is not nil, we have more tokens to process
+
+rem  if this is not nu;ll, we have more tokens to process
 rem  start above process again with remaining unprocessed cl args
 if defined cl_args goto :process_cl_args
 

etc/spack/defaults/concretizer.yaml

@@ -36,3 +36,9 @@ concretizer:
   # on each root spec, allowing different versions and variants of the same package in
   # an environment.
   unify: true
+  # Option to deal with possible duplicate nodes (i.e. different nodes from the same package) in the DAG.
+  duplicates:
+    # "none": allows a single node for any package in the DAG.
+    # "minimal": allows the duplication of 'build-tools' nodes only (e.g. py-setuptools, cmake etc.)
+    # "full" (experimental): allows separation of the entire build-tool stack (e.g. the entire "cmake" subDAG)
+    strategy: none

etc/spack/defaults/packages.yaml

@@ -60,7 +60,7 @@ packages:
       xxd: [xxd-standalone, vim]
       yacc: [bison, byacc]
       ziglang: [zig]
-      zlib-api: [zlib, zlib-ng+compat]
+      zlib-api: [zlib-ng+compat, zlib]
     permissions:
       read: world
       write: user

lib/spack/docs/requirements.txt

@@ -1,7 +1,7 @@
-sphinx==6.2.1
+sphinx==7.2.2
 sphinxcontrib-programoutput==0.17
 sphinx_design==0.5.0
-sphinx-rtd-theme==1.2.2
+sphinx-rtd-theme==1.3.0
 python-levenshtein==0.21.1
 docutils==0.18.1
 pygments==2.16.1
@@ -10,4 +10,4 @@ pytest==7.4.0
 isort==5.12.0
 black==23.7.0
 flake8==6.1.0
-mypy==1.5.0
+mypy==1.5.1

lib/spack/llnl/util/filesystem.py

@@ -1754,9 +1754,14 @@ def find(root, files, recursive=True):
         files = [files]
 
     if recursive:
-        return _find_recursive(root, files)
+        tty.debug(f"Find (recursive): {root} {str(files)}")
+        result = _find_recursive(root, files)
     else:
-        return _find_non_recursive(root, files)
+        tty.debug(f"Find (not recursive): {root} {str(files)}")
+        result = _find_non_recursive(root, files)
+
+    tty.debug(f"Find complete: {root} {str(files)}")
+    return result
 
 
 @system_path_filter

lib/spack/llnl/util/tty/log.py

@@ -780,7 +780,7 @@ def __enter__(self):
             raise RuntimeError("file argument must be set by __init__ ")
 
         # Open both write and reading on logfile
-        if type(self.logfile) == io.StringIO:
+        if isinstance(self.logfile, io.StringIO):
             self._ioflag = True
             # cannot have two streams on tempfile, so we must make our own
             sys.stdout = self.logfile

lib/spack/spack/binary_distribution.py

@@ -2383,22 +2383,12 @@ def __init__(self, all_architectures):
 
         self.possible_specs = specs
 
-    def __call__(self, spec, **kwargs):
+    def __call__(self, spec: Spec, **kwargs):
         """
         Args:
-            spec (str): The spec being searched for in its string representation or hash.
+            spec: The spec being searched for
         """
-        matches = []
-        if spec.startswith("/"):
-            # Matching a DAG hash
-            query_hash = spec.replace("/", "")
-            for candidate_spec in self.possible_specs:
-                if candidate_spec.dag_hash().startswith(query_hash):
-                    matches.append(candidate_spec)
-        else:
-            # Matching a spec constraint
-            matches = [s for s in self.possible_specs if s.satisfies(spec)]
-        return matches
+        return [s for s in self.possible_specs if s.satisfies(spec)]
 
 
 class FetchIndexError(Exception):

lib/spack/spack/bootstrap/config.py

@@ -124,9 +124,9 @@ def _read_and_sanitize_configuration() -> Dict[str, Any]:
 def _bootstrap_config_scopes() -> Sequence["spack.config.ConfigScope"]:
     tty.debug("[BOOTSTRAP CONFIG SCOPE] name=_builtin")
     config_scopes: MutableSequence["spack.config.ConfigScope"] = [
-        spack.config.InternalConfigScope("_builtin", spack.config.config_defaults)
+        spack.config.InternalConfigScope("_builtin", spack.config.CONFIG_DEFAULTS)
     ]
-    configuration_paths = (spack.config.configuration_defaults_path, ("bootstrap", _config_path()))
+    configuration_paths = (spack.config.CONFIGURATION_DEFAULTS_PATH, ("bootstrap", _config_path()))
     for name, path in configuration_paths:
         platform = spack.platforms.host().name
         platform_scope = spack.config.ConfigScope(

lib/spack/spack/bootstrap/core.py

@@ -480,11 +480,18 @@ def _add_externals_if_missing() -> None:
         spack.repo.PATH.get_pkg_class("bison"),
         # GnuPG
         spack.repo.PATH.get_pkg_class("gawk"),
+        # develop deps
+        spack.repo.PATH.get_pkg_class("git"),
     ]
     if IS_WINDOWS:
         search_list.append(spack.repo.PATH.get_pkg_class("winbison"))
-    detected_packages = spack.detection.by_executable(search_list)
-    spack.detection.update_configuration(detected_packages, scope="bootstrap")
+    externals = spack.detection.by_executable(search_list)
+    # System git is typically deprecated, so mark as non-buildable to force it as external
+    non_buildable_externals = {k: externals.pop(k) for k in ("git",) if k in externals}
+    spack.detection.update_configuration(externals, scope="bootstrap", buildable=True)
+    spack.detection.update_configuration(
+        non_buildable_externals, scope="bootstrap", buildable=False
+    )
 
 
 def clingo_root_spec() -> str:

lib/spack/spack/bootstrap/environment.py

@@ -23,6 +23,7 @@
 
 from ._common import _root_spec
 from .config import root_path, spec_for_current_python, store_path
+from .core import _add_externals_if_missing
 
 
 class BootstrapEnvironment(spack.environment.Environment):
@@ -185,6 +186,7 @@ def pytest_root_spec() -> str:
 
 def ensure_environment_dependencies() -> None:
     """Ensure Spack dependencies from the bootstrap environment are installed and ready to use"""
+    _add_externals_if_missing()
     with BootstrapEnvironment() as env:
         env.update_installations()
         env.update_syspath_and_environ()

lib/spack/spack/build_environment.py

@@ -1027,7 +1027,7 @@ def get_cmake_prefix_path(pkg):
 
 
 def _setup_pkg_and_run(
-    serialized_pkg, function, kwargs, child_pipe, input_multiprocess_fd, jsfd1, jsfd2
+    serialized_pkg, function, kwargs, write_pipe, input_multiprocess_fd, jsfd1, jsfd2
 ):
     context = kwargs.get("context", "build")
 
@@ -1048,12 +1048,12 @@ def _setup_pkg_and_run(
                 pkg, dirty=kwargs.get("dirty", False), context=context
             )
         return_value = function(pkg, kwargs)
-        child_pipe.send(return_value)
+        write_pipe.send(return_value)
 
     except StopPhase as e:
         # Do not create a full ChildError from this, it's not an error
         # it's a control statement.
-        child_pipe.send(e)
+        write_pipe.send(e)
     except BaseException:
         # catch ANYTHING that goes wrong in the child process
         exc_type, exc, tb = sys.exc_info()
@@ -1102,10 +1102,10 @@ def _setup_pkg_and_run(
             context,
             package_context,
         )
-        child_pipe.send(ce)
+        write_pipe.send(ce)
 
     finally:
-        child_pipe.close()
+        write_pipe.close()
         if input_multiprocess_fd is not None:
             input_multiprocess_fd.close()
 
@@ -1149,7 +1149,7 @@ def child_fun():
     For more information on `multiprocessing` child process creation
     mechanisms, see https://docs.python.org/3/library/multiprocessing.html#contexts-and-start-methods
     """
-    parent_pipe, child_pipe = multiprocessing.Pipe()
+    read_pipe, write_pipe = multiprocessing.Pipe(duplex=False)
     input_multiprocess_fd = None
     jobserver_fd1 = None
     jobserver_fd2 = None
@@ -1174,7 +1174,7 @@ def child_fun():
                 serialized_pkg,
                 function,
                 kwargs,
-                child_pipe,
+                write_pipe,
                 input_multiprocess_fd,
                 jobserver_fd1,
                 jobserver_fd2,
@@ -1183,6 +1183,12 @@ def child_fun():
 
         p.start()
 
+        # We close the writable end of the pipe now to be sure that p is the
+        # only process which owns a handle for it. This ensures that when p
+        # closes its handle for the writable end, read_pipe.recv() will
+        # promptly report the readable end as being ready.
+        write_pipe.close()
+
     except InstallError as e:
         e.pkg = pkg
         raise
@@ -1192,7 +1198,16 @@ def child_fun():
         if input_multiprocess_fd is not None:
             input_multiprocess_fd.close()
 
-    child_result = parent_pipe.recv()
+    def exitcode_msg(p):
+        typ = "exit" if p.exitcode >= 0 else "signal"
+        return f"{typ} {abs(p.exitcode)}"
+
+    try:
+        child_result = read_pipe.recv()
+    except EOFError:
+        p.join()
+        raise InstallError(f"The process has stopped unexpectedly ({exitcode_msg(p)})")
+
     p.join()
 
     # If returns a StopPhase, raise it
@@ -1212,6 +1227,10 @@ def child_fun():
         child_result.print_context()
         raise child_result
 
+    # Fallback. Usually caught beforehand in EOFError above.
+    if p.exitcode != 0:
+        raise InstallError(f"The process failed unexpectedly ({exitcode_msg(p)})")
+
     return child_result
 
 

lib/spack/spack/build_systems/autotools.py

@@ -55,7 +55,8 @@ def flags_to_build_system_args(self, flags):
         setattr(self, "configure_flag_args", [])
         for flag, values in flags.items():
             if values:
-                values_str = "{0}={1}".format(flag.upper(), " ".join(values))
+                var_name = "LIBS" if flag == "ldlibs" else flag.upper()
+                values_str = "{0}={1}".format(var_name, " ".join(values))
                 self.configure_flag_args.append(values_str)
         # Spack's fflags are meant for both F77 and FC, therefore we
         # additionaly set FCFLAGS if required.

lib/spack/spack/caches.py

@@ -20,9 +20,9 @@
 
 
 def misc_cache_location():
-    """The ``misc_cache`` is Spack's cache for small data.
+    """The ``MISC_CACHE`` is Spack's cache for small data.
 
-    Currently the ``misc_cache`` stores indexes for virtual dependency
+    Currently the ``MISC_CACHE`` stores indexes for virtual dependency
     providers and for which packages provide which tags.
     """
     path = spack.config.get("config:misc_cache", spack.paths.default_misc_cache_path)
@@ -35,7 +35,7 @@ def _misc_cache():
 
 
 #: Spack's cache for small data
-misc_cache: Union[
+MISC_CACHE: Union[
     spack.util.file_cache.FileCache, llnl.util.lang.Singleton
 ] = llnl.util.lang.Singleton(_misc_cache)
 
@@ -91,6 +91,6 @@ def symlink(self, mirror_ref):
 
 
 #: Spack's local cache for downloaded source archives
-fetch_cache: Union[
+FETCH_CACHE: Union[
     spack.fetch_strategy.FsCache, llnl.util.lang.Singleton
 ] = llnl.util.lang.Singleton(_fetch_cache)

lib/spack/spack/cmd/bootstrap.py

@@ -69,11 +69,10 @@
 
 def _add_scope_option(parser):
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
     parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         help="configuration scope to read/modify",
     )
 
@@ -170,7 +169,7 @@ def _reset(args):
         if not ok_to_continue:
             raise RuntimeError("Aborting")
 
-    for scope in spack.config.config.file_scopes:
+    for scope in spack.config.CONFIG.file_scopes:
         # The default scope should stay untouched
         if scope.name == "defaults":
             continue
@@ -187,7 +186,7 @@ def _reset(args):
         if os.path.exists(bootstrap_yaml):
             shutil.move(bootstrap_yaml, backup_file)
 
-        spack.config.config.clear_caches()
+        spack.config.CONFIG.clear_caches()
 
 
 def _root(args):

lib/spack/spack/cmd/buildcache.py

@@ -149,12 +149,11 @@ def setup_parser(subparser: argparse.ArgumentParser):
 
     # used to construct scope arguments below
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
 
     check.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope(),
         help="configuration scope containing mirrors to check",
     )

lib/spack/spack/cmd/clean.py

@@ -118,7 +118,7 @@ def clean(parser, args):
 
     if args.downloads:
         tty.msg("Removing cached downloads")
-        spack.caches.fetch_cache.destroy()
+        spack.caches.FETCH_CACHE.destroy()
 
     if args.failures:
         tty.msg("Removing install failure marks")
@@ -126,7 +126,7 @@ def clean(parser, args):
 
     if args.misc_cache:
         tty.msg("Removing cached information on repositories")
-        spack.caches.misc_cache.destroy()
+        spack.caches.MISC_CACHE.destroy()
 
     if args.python_cache:
         tty.msg("Removing python cache files")

lib/spack/spack/cmd/compiler.py

@@ -24,7 +24,6 @@ def setup_parser(subparser):
     sp = subparser.add_subparsers(metavar="SUBCOMMAND", dest="compiler_command")
 
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
 
     # Find
     find_parser = sp.add_parser(
@@ -36,7 +35,7 @@ def setup_parser(subparser):
     find_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope("compilers"),
         help="configuration scope to modify",
     )
@@ -50,7 +49,7 @@ def setup_parser(subparser):
     remove_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=None,
         help="configuration scope to modify",
     )
@@ -60,7 +59,7 @@ def setup_parser(subparser):
     list_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_list_scope(),
         help="configuration scope to read from",
     )
@@ -71,7 +70,7 @@ def setup_parser(subparser):
     info_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_list_scope(),
         help="configuration scope to read from",
     )
@@ -93,7 +92,7 @@ def compiler_find(args):
         n = len(new_compilers)
         s = "s" if n > 1 else ""
 
-        config = spack.config.config
+        config = spack.config.CONFIG
         filename = config.get_config_filename(args.scope, "compilers")
         tty.msg("Added %d new compiler%s to %s" % (n, s, filename))
         colify(reversed(sorted(c.spec.display_str for c in new_compilers)), indent=4)

lib/spack/spack/cmd/compilers.py

@@ -13,12 +13,11 @@
 
 def setup_parser(subparser):
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
 
     subparser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         help="configuration scope to read/modify",
     )
 

lib/spack/spack/cmd/config.py

@@ -27,13 +27,12 @@
 
 def setup_parser(subparser):
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
 
     # User can only choose one
     subparser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         help="configuration scope to read/modify",
     )
 
@@ -45,7 +44,7 @@ def setup_parser(subparser):
         help="configuration section to print\n\noptions: %(choices)s",
         nargs="?",
         metavar="section",
-        choices=spack.config.section_schemas,
+        choices=spack.config.SECTION_SCHEMAS,
     )
 
     blame_parser = sp.add_parser(
@@ -55,7 +54,7 @@ def setup_parser(subparser):
         "section",
         help="configuration section to print\n\noptions: %(choices)s",
         metavar="section",
-        choices=spack.config.section_schemas,
+        choices=spack.config.SECTION_SCHEMAS,
     )
 
     edit_parser = sp.add_parser("edit", help="edit configuration file")
@@ -64,7 +63,7 @@ def setup_parser(subparser):
         help="configuration section to edit\n\noptions: %(choices)s",
         metavar="section",
         nargs="?",
-        choices=spack.config.section_schemas,
+        choices=spack.config.SECTION_SCHEMAS,
     )
     edit_parser.add_argument(
         "--print-file", action="store_true", help="print the file name that would be edited"
@@ -146,10 +145,10 @@ def config_get(args):
     scope, section = _get_scope_and_section(args)
 
     if section is not None:
-        spack.config.config.print_section(section)
+        spack.config.CONFIG.print_section(section)
 
     elif scope and scope.startswith("env:"):
-        config_file = spack.config.config.get_config_filename(scope, section)
+        config_file = spack.config.CONFIG.get_config_filename(scope, section)
         if os.path.exists(config_file):
             with open(config_file) as f:
                 print(f.read())
@@ -162,7 +161,7 @@ def config_get(args):
 
 def config_blame(args):
     """Print out line-by-line blame of merged YAML."""
-    spack.config.config.print_section(args.section, blame=True)
+    spack.config.CONFIG.print_section(args.section, blame=True)
 
 
 def config_edit(args):
@@ -181,7 +180,7 @@ def config_edit(args):
         scope, section = _get_scope_and_section(args)
         if not scope and not section:
             tty.die("`spack config edit` requires a section argument or an active environment.")
-        config_file = spack.config.config.get_config_filename(scope, section)
+        config_file = spack.config.CONFIG.get_config_filename(scope, section)
 
     if args.print_file:
         print(config_file)
@@ -194,7 +193,7 @@ def config_list(args):
 
     Used primarily for shell tab completion scripts.
     """
-    print(" ".join(list(spack.config.section_schemas)))
+    print(" ".join(list(spack.config.SECTION_SCHEMAS)))
 
 
 def config_add(args):
@@ -251,19 +250,19 @@ def _can_update_config_file(scope: spack.config.ConfigScope, cfg_file):
 
 def config_update(args):
     # Read the configuration files
-    spack.config.config.get_config(args.section, scope=args.scope)
+    spack.config.CONFIG.get_config(args.section, scope=args.scope)
     updates: List[spack.config.ConfigScope] = list(
         filter(
             lambda s: not isinstance(
                 s, (spack.config.InternalConfigScope, spack.config.ImmutableConfigScope)
             ),
-            spack.config.config.format_updates[args.section],
+            spack.config.CONFIG.format_updates[args.section],
         )
     )
 
     cannot_overwrite, skip_system_scope = [], False
     for scope in updates:
-        cfg_file = spack.config.config.get_config_filename(scope.name, args.section)
+        cfg_file = spack.config.CONFIG.get_config_filename(scope.name, args.section)
         can_be_updated = _can_update_config_file(scope, cfg_file)
         if not can_be_updated:
             if scope.name == "system":
@@ -302,7 +301,7 @@ def config_update(args):
             " the latest schema format:\n\n"
         )
         for scope in updates:
-            cfg_file = spack.config.config.get_config_filename(scope.name, args.section)
+            cfg_file = spack.config.CONFIG.get_config_filename(scope.name, args.section)
             msg += "\t[scope={0}, file={1}]\n".format(scope.name, cfg_file)
         msg += (
             "\nIf the configuration files are updated, versions of Spack "
@@ -325,7 +324,7 @@ def config_update(args):
         # Make a backup copy and rewrite the file
         bkp_file = cfg_file + ".bkp"
         shutil.copy(cfg_file, bkp_file)
-        spack.config.config.update_config(args.section, data, scope=scope.name, force=True)
+        spack.config.CONFIG.update_config(args.section, data, scope=scope.name, force=True)
         tty.msg(f'File "{cfg_file}" update [backup={bkp_file}]')
 
 
@@ -337,13 +336,13 @@ def _can_revert_update(scope_dir, cfg_file, bkp_file):
 
 
 def config_revert(args):
-    scopes = [args.scope] if args.scope else [x.name for x in spack.config.config.file_scopes]
+    scopes = [args.scope] if args.scope else [x.name for x in spack.config.CONFIG.file_scopes]
 
     # Search for backup files in the configuration scopes
     Entry = collections.namedtuple("Entry", ["scope", "cfg", "bkp"])
     to_be_restored, cannot_overwrite = [], []
     for scope in scopes:
-        cfg_file = spack.config.config.get_config_filename(scope, args.section)
+        cfg_file = spack.config.CONFIG.get_config_filename(scope, args.section)
         bkp_file = cfg_file + ".bkp"
 
         # If the backup files doesn't exist move to the next scope
@@ -457,7 +456,7 @@ def config_prefer_upstream(args):
     existing = spack.config.get("packages", scope=scope)
     new = spack.config.merge_yaml(existing, pkgs)
     spack.config.set("packages", new, scope)
-    config_file = spack.config.config.get_config_filename(scope, section)
+    config_file = spack.config.CONFIG.get_config_filename(scope, section)
 
     tty.msg("Updated config at {0}".format(config_file))
 

lib/spack/spack/cmd/external.py

@@ -13,6 +13,7 @@
 import spack
 import spack.cmd
 import spack.cmd.common.arguments
+import spack.config
 import spack.cray_manifest as cray_manifest
 import spack.detection
 import spack.error
@@ -27,7 +28,6 @@ def setup_parser(subparser):
     sp = subparser.add_subparsers(metavar="SUBCOMMAND", dest="external_command")
 
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
 
     find_parser = sp.add_parser("find", help="add external packages to packages.yaml")
     find_parser.add_argument(
@@ -47,7 +47,7 @@ def setup_parser(subparser):
     find_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope("packages"),
         help="configuration scope to modify",
     )
@@ -165,7 +165,7 @@ def external_find(args):
         detected_packages, scope=args.scope, buildable=not args.not_buildable
     )
     if new_entries:
-        path = spack.config.config.get_config_filename(args.scope, "packages")
+        path = spack.config.CONFIG.get_config_filename(args.scope, "packages")
         msg = "The following specs have been detected on this system and added to {0}"
         tty.msg(msg.format(path))
         spack.cmd.display_specs(new_entries)

lib/spack/spack/cmd/mirror.py

@@ -90,7 +90,6 @@ def setup_parser(subparser):
 
     # used to construct scope arguments below
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
 
     # Add
     add_parser = sp.add_parser("add", help=mirror_add.__doc__)
@@ -99,7 +98,7 @@ def setup_parser(subparser):
     add_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope(),
         help="configuration scope to modify",
     )
@@ -119,7 +118,7 @@ def setup_parser(subparser):
     remove_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope(),
         help="configuration scope to modify",
     )
@@ -138,7 +137,7 @@ def setup_parser(subparser):
     set_url_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope(),
         help="configuration scope to modify",
     )
@@ -167,7 +166,7 @@ def setup_parser(subparser):
     set_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope(),
         help="configuration scope to modify",
     )
@@ -178,7 +177,7 @@ def setup_parser(subparser):
     list_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_list_scope(),
         help="configuration scope to read from",
     )
@@ -444,7 +443,7 @@ def mirror_create(args):
         )
 
     # When no directory is provided, the source dir is used
-    path = args.directory or spack.caches.fetch_cache_location()
+    path = args.directory or spack.caches.FETCH_CACHE_location()
 
     if args.all and not ev.active_environment():
         create_mirror_for_all_specs(

lib/spack/spack/cmd/repo.py

@@ -20,7 +20,6 @@
 def setup_parser(subparser):
     sp = subparser.add_subparsers(metavar="SUBCOMMAND", dest="repo_command")
     scopes = spack.config.scopes()
-    scopes_metavar = spack.config.scopes_metavar
 
     # Create
     create_parser = sp.add_parser("create", help=repo_create.__doc__)
@@ -45,7 +44,7 @@ def setup_parser(subparser):
     list_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_list_scope(),
         help="configuration scope to read from",
     )
@@ -56,7 +55,7 @@ def setup_parser(subparser):
     add_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope(),
         help="configuration scope to modify",
     )
@@ -69,7 +68,7 @@ def setup_parser(subparser):
     remove_parser.add_argument(
         "--scope",
         choices=scopes,
-        metavar=scopes_metavar,
+        metavar=spack.config.SCOPES_METAVAR,
         default=spack.config.default_modify_scope(),
         help="configuration scope to modify",
     )

lib/spack/spack/cmd/unit_test.py

@@ -209,12 +209,11 @@ def unit_test(parser, args, unknown_args):
     # mock configuration used by unit tests
     # Note: skip on windows here because for the moment,
     # clingo is wholly unsupported from bootstrap
-    if sys.platform != "win32":
-        with spack.bootstrap.ensure_bootstrap_configuration():
-            spack.bootstrap.ensure_core_dependencies()
-            if pytest is None:
-                spack.bootstrap.ensure_environment_dependencies()
-                import pytest
+    with spack.bootstrap.ensure_bootstrap_configuration():
+        spack.bootstrap.ensure_core_dependencies()
+        if pytest is None:
+            spack.bootstrap.ensure_environment_dependencies()
+            import pytest
 
     if args.pytest_help:
         # make the pytest.main help output more accurate

lib/spack/spack/compilers/__init__.py

@@ -135,7 +135,7 @@ def _init_compiler_config(*, scope):
 
 def compiler_config_files():
     config_files = list()
-    config = spack.config.config
+    config = spack.config.CONFIG
     for scope in config.file_scopes:
         name = scope.name
         compiler_config = config.get("compilers", scope=name)
@@ -169,7 +169,7 @@ def remove_compiler_from_config(compiler_spec, scope=None):
     """
     candidate_scopes = [scope]
     if scope is None:
-        candidate_scopes = spack.config.config.scopes.keys()
+        candidate_scopes = spack.config.CONFIG.scopes.keys()
 
     removal_happened = False
     for current_scope in candidate_scopes:
@@ -523,7 +523,7 @@ def compiler_for_spec(compiler_spec, arch_spec):
 
 @_auto_compiler_spec
 def get_compiler_duplicates(compiler_spec, arch_spec):
-    config = spack.config.config
+    config = spack.config.CONFIG
 
     scope_to_compilers = {}
     for scope in config.scopes:

lib/spack/spack/concretize.py

@@ -28,6 +28,7 @@
 
 import spack.abi
 import spack.compilers
+import spack.config
 import spack.environment
 import spack.error
 import spack.platforms
@@ -37,7 +38,6 @@
 import spack.tengine
 import spack.util.path
 import spack.variant as vt
-from spack.config import config
 from spack.package_prefs import PackagePrefs, is_spec_buildable, spec_externals
 from spack.version import ClosedOpenRange, VersionList, ver
 
@@ -76,7 +76,7 @@ class Concretizer:
 
     def __init__(self, abstract_spec=None):
         if Concretizer.check_for_compiler_existence is None:
-            Concretizer.check_for_compiler_existence = not config.get(
+            Concretizer.check_for_compiler_existence = not spack.config.get(
                 "config:install_missing_compilers", False
             )
         self.abstract_spec = abstract_spec

lib/spack/spack/config.py

@@ -47,6 +47,8 @@
 import spack.platforms
 import spack.schema
 import spack.schema.bootstrap
+import spack.schema.cdash
+import spack.schema.ci
 import spack.schema.compilers
 import spack.schema.concretizer
 import spack.schema.config
@@ -64,7 +66,7 @@
 from spack.util.cpus import cpus_available
 
 #: Dict from section names -> schema for that section
-section_schemas = {
+SECTION_SCHEMAS = {
     "compilers": spack.schema.compilers.schema,
     "concretizer": spack.schema.concretizer.schema,
     "mirrors": spack.schema.mirrors.schema,
@@ -80,16 +82,16 @@
 
 # Same as above, but including keys for environments
 # this allows us to unify config reading between configs and environments
-all_schemas = copy.deepcopy(section_schemas)
-all_schemas.update({spack.schema.env.TOP_LEVEL_KEY: spack.schema.env.schema})
+_ALL_SCHEMAS = copy.deepcopy(SECTION_SCHEMAS)
+_ALL_SCHEMAS.update({spack.schema.env.TOP_LEVEL_KEY: spack.schema.env.schema})
 
 #: Path to the default configuration
-configuration_defaults_path = ("defaults", os.path.join(spack.paths.etc_path, "defaults"))
+CONFIGURATION_DEFAULTS_PATH = ("defaults", os.path.join(spack.paths.etc_path, "defaults"))
 
 #: Hard-coded default values for some key configuration options.
 #: This ensures that Spack will still work even if config.yaml in
 #: the defaults scope is removed.
-config_defaults = {
+CONFIG_DEFAULTS = {
     "config": {
         "debug": False,
         "connect_timeout": 10,
@@ -105,10 +107,10 @@
 
 #: metavar to use for commands that accept scopes
 #: this is shorter and more readable than listing all choices
-scopes_metavar = "{defaults,system,site,user}[/PLATFORM] or env:ENVIRONMENT"
+SCOPES_METAVAR = "{defaults,system,site,user}[/PLATFORM] or env:ENVIRONMENT"
 
 #: Base name for the (internal) overrides scope.
-overrides_base_name = "overrides-"
+_OVERRIDES_BASE_NAME = "overrides-"
 
 
 class ConfigScope:
@@ -134,7 +136,7 @@ def get_section_filename(self, section):
     def get_section(self, section):
         if section not in self.sections:
             path = self.get_section_filename(section)
-            schema = section_schemas[section]
+            schema = SECTION_SCHEMAS[section]
             data = read_config_file(path, schema)
             self.sections[section] = data
         return self.sections[section]
@@ -145,7 +147,7 @@ def _write_section(self, section):
 
         # We copy data here to avoid adding defaults at write time
         validate_data = copy.deepcopy(data)
-        validate(validate_data, section_schemas[section])
+        validate(validate_data, SECTION_SCHEMAS[section])
 
         try:
             mkdirp(self.path)
@@ -317,7 +319,7 @@ def __init__(self, name, data=None):
             data = InternalConfigScope._process_dict_keyname_overrides(data)
             for section in data:
                 dsec = data[section]
-                validate({section: dsec}, section_schemas[section])
+                validate({section: dsec}, SECTION_SCHEMAS[section])
                 self.sections[section] = _mark_internal(syaml.syaml_dict({section: dsec}), name)
 
     def get_section_filename(self, section):
@@ -333,7 +335,7 @@ def _write_section(self, section):
         """This only validates, as the data is already in memory."""
         data = self.get_section(section)
         if data is not None:
-            validate(data, section_schemas[section])
+            validate(data, SECTION_SCHEMAS[section])
         self.sections[section] = _mark_internal(data, self.name)
 
     def __repr__(self):
@@ -430,7 +432,7 @@ def file_scopes(self) -> List[ConfigScope]:
         return [
             s
             for s in self.scopes.values()
-            if (type(s) == ConfigScope or type(s) == SingleFileScope)
+            if (type(s) is ConfigScope or type(s) is SingleFileScope)
         ]
 
     def highest_precedence_scope(self) -> ConfigScope:
@@ -711,11 +713,11 @@ def override(path_or_scope, value=None):
     """
     if isinstance(path_or_scope, ConfigScope):
         overrides = path_or_scope
-        config.push_scope(path_or_scope)
+        CONFIG.push_scope(path_or_scope)
     else:
-        base_name = overrides_base_name
+        base_name = _OVERRIDES_BASE_NAME
         # Ensure the new override gets a unique scope name
-        current_overrides = [s.name for s in config.matching_scopes(r"^{0}".format(base_name))]
+        current_overrides = [s.name for s in CONFIG.matching_scopes(r"^{0}".format(base_name))]
         num_overrides = len(current_overrides)
         while True:
             scope_name = "{0}{1}".format(base_name, num_overrides)
@@ -725,19 +727,19 @@ def override(path_or_scope, value=None):
                 break
 
         overrides = InternalConfigScope(scope_name)
-        config.push_scope(overrides)
-        config.set(path_or_scope, value, scope=scope_name)
+        CONFIG.push_scope(overrides)
+        CONFIG.set(path_or_scope, value, scope=scope_name)
 
     try:
-        yield config
+        yield CONFIG
     finally:
-        scope = config.remove_scope(overrides.name)
+        scope = CONFIG.remove_scope(overrides.name)
         assert scope is overrides
 
 
 #: configuration scopes added on the command line
 #: set by ``spack.main.main()``.
-command_line_scopes: List[str] = []
+COMMAND_LINE_SCOPES: List[str] = []
 
 
 def _add_platform_scope(cfg, scope_type, name, path):
@@ -781,14 +783,14 @@ def create():
     cfg = Configuration()
 
     # first do the builtin, hardcoded defaults
-    builtin = InternalConfigScope("_builtin", config_defaults)
+    builtin = InternalConfigScope("_builtin", CONFIG_DEFAULTS)
     cfg.push_scope(builtin)
 
     # Builtin paths to configuration files in Spack
     configuration_paths = [
         # Default configuration scope is the lowest-level scope. These are
         # versioned with Spack and can be overridden by systems, sites or users
-        configuration_defaults_path
+        CONFIGURATION_DEFAULTS_PATH
     ]
 
     disable_local_config = "SPACK_DISABLE_LOCAL_CONFIG" in os.environ
@@ -815,7 +817,7 @@ def create():
         _add_platform_scope(cfg, ConfigScope, name, path)
 
     # add command-line scopes
-    _add_command_line_scopes(cfg, command_line_scopes)
+    _add_command_line_scopes(cfg, COMMAND_LINE_SCOPES)
 
     # we make a special scope for spack commands so that they can
     # override configuration options.
@@ -825,7 +827,7 @@ def create():
 
 
 #: This is the singleton configuration instance for Spack.
-config: Union[Configuration, llnl.util.lang.Singleton] = llnl.util.lang.Singleton(create)
+CONFIG: Union[Configuration, llnl.util.lang.Singleton] = llnl.util.lang.Singleton(create)
 
 
 def add_from_file(filename, scope=None):
@@ -838,7 +840,7 @@ def add_from_file(filename, scope=None):
     # update all sections from config dict
     # We have to iterate on keys to keep overrides from the file
     for section in data.keys():
-        if section in section_schemas.keys():
+        if section in SECTION_SCHEMAS.keys():
             # Special handling for compiler scope difference
             # Has to be handled after we choose a section
             if scope is None:
@@ -849,7 +851,7 @@ def add_from_file(filename, scope=None):
             new = merge_yaml(existing, value)
 
             # We cannot call config.set directly (set is a type)
-            config.set(section, new, scope)
+            CONFIG.set(section, new, scope)
 
 
 def add(fullpath, scope=None):
@@ -897,12 +899,12 @@ def add(fullpath, scope=None):
 
     # merge value into existing
     new = merge_yaml(existing, value)
-    config.set(path, new, scope)
+    CONFIG.set(path, new, scope)
 
 
 def get(path, default=None, scope=None):
     """Module-level wrapper for ``Configuration.get()``."""
-    return config.get(path, default, scope)
+    return CONFIG.get(path, default, scope)
 
 
 def set(path, value, scope=None):
@@ -910,26 +912,26 @@ def set(path, value, scope=None):
 
     Accepts the path syntax described in ``get()``.
     """
-    return config.set(path, value, scope)
+    return CONFIG.set(path, value, scope)
 
 
 def add_default_platform_scope(platform):
     plat_name = os.path.join("defaults", platform)
-    plat_path = os.path.join(configuration_defaults_path[1], platform)
-    config.push_scope(ConfigScope(plat_name, plat_path))
+    plat_path = os.path.join(CONFIGURATION_DEFAULTS_PATH[1], platform)
+    CONFIG.push_scope(ConfigScope(plat_name, plat_path))
 
 
 def scopes():
     """Convenience function to get list of configuration scopes."""
-    return config.scopes
+    return CONFIG.scopes
 
 
 def _validate_section_name(section):
     """Exit if the section is not a valid section."""
-    if section not in section_schemas:
+    if section not in SECTION_SCHEMAS:
         raise ConfigSectionError(
             "Invalid config section: '%s'. Options are: %s"
-            % (section, " ".join(section_schemas.keys()))
+            % (section, " ".join(SECTION_SCHEMAS.keys()))
         )
 
 
@@ -990,7 +992,7 @@ def read_config_file(filename, schema=None):
         if data:
             if not schema:
                 key = next(iter(data))
-                schema = all_schemas[key]
+                schema = _ALL_SCHEMAS[key]
             validate(data, schema)
         return data
 
@@ -1089,7 +1091,7 @@ def get_valid_type(path):
         test_data = {component: test_data}
 
     try:
-        validate(test_data, section_schemas[section])
+        validate(test_data, SECTION_SCHEMAS[section])
     except (ConfigFormatError, AttributeError) as e:
         jsonschema_error = e.validation_error
         if jsonschema_error.validator == "type":
@@ -1278,9 +1280,9 @@ def default_modify_scope(section="config"):
             If this is not 'compilers', a general (non-platform) scope is used.
     """
     if section == "compilers":
-        return spack.config.config.highest_precedence_scope().name
+        return CONFIG.highest_precedence_scope().name
     else:
-        return spack.config.config.highest_precedence_non_platform_scope().name
+        return CONFIG.highest_precedence_non_platform_scope().name
 
 
 def default_list_scope():
@@ -1337,18 +1339,18 @@ def use_configuration(*scopes_or_paths):
     Returns:
         Configuration object associated with the scopes passed as arguments
     """
-    global config
+    global CONFIG
 
     # Normalize input and construct a Configuration object
     configuration = _config_from(scopes_or_paths)
-    config.clear_caches(), configuration.clear_caches()
+    CONFIG.clear_caches(), configuration.clear_caches()
 
-    saved_config, config = config, configuration
+    saved_config, CONFIG = CONFIG, configuration
 
     try:
         yield configuration
     finally:
-        config = saved_config
+        CONFIG = saved_config
 
 
 @llnl.util.lang.memoized

lib/spack/spack/container/writers/__init__.py

@@ -5,8 +5,8 @@
 """Writers for different kind of recipes and related
 convenience functions.
 """
-import collections
 import copy
+from collections import namedtuple
 from typing import Optional
 
 import spack.environment as ev
@@ -159,13 +159,13 @@ def depfile(self):
     @tengine.context_property
     def run(self):
         """Information related to the run image."""
-        Run = collections.namedtuple("Run", ["image"])
+        Run = namedtuple("Run", ["image"])
         return Run(image=self.final_image)
 
     @tengine.context_property
     def build(self):
         """Information related to the build image."""
-        Build = collections.namedtuple("Build", ["image"])
+        Build = namedtuple("Build", ["image"])
         return Build(image=self.build_image)
 
     @tengine.context_property
@@ -176,12 +176,13 @@ def strip(self):
     @tengine.context_property
     def paths(self):
         """Important paths in the image"""
-        Paths = collections.namedtuple("Paths", ["environment", "store", "hidden_view", "view"])
+        Paths = namedtuple("Paths", ["environment", "store", "view_parent", "view", "former_view"])
         return Paths(
             environment="/opt/spack-environment",
             store="/opt/software",
-            hidden_view="/opt/._view",
-            view="/opt/view",
+            view_parent="/opt/views",
+            view="/opt/views/view",
+            former_view="/opt/view",  # /opt/view -> /opt/views/view for backward compatibility
         )
 
     @tengine.context_property
@@ -257,7 +258,7 @@ def _package_info_from(self, package_list):
 
         update, install, clean = commands_for(os_pkg_manager)
 
-        Packages = collections.namedtuple("Packages", ["update", "install", "list", "clean"])
+        Packages = namedtuple("Packages", ["update", "install", "list", "clean"])
         return Packages(update=update, install=install, list=package_list, clean=clean)
 
     def _os_pkg_manager(self):
@@ -273,7 +274,7 @@ def _os_pkg_manager(self):
 
     @tengine.context_property
     def extra_instructions(self):
-        Extras = collections.namedtuple("Extra", ["build", "final"])
+        Extras = namedtuple("Extra", ["build", "final"])
         extras = self.container_config.get("extra_instructions", {})
         build, final = extras.get("build", None), extras.get("final", None)
         return Extras(build=build, final=final)
@@ -295,7 +296,7 @@ def bootstrap(self):
             context = {"bootstrap": {"image": self.bootstrap_image, "spack_checkout": command}}
             bootstrap_recipe = env.get_template(template_path).render(**context)
 
-        Bootstrap = collections.namedtuple("Bootstrap", ["image", "recipe"])
+        Bootstrap = namedtuple("Bootstrap", ["image", "recipe"])
         return Bootstrap(image=self.bootstrap_image, recipe=bootstrap_recipe)
 
     @tengine.context_property
@@ -303,7 +304,7 @@ def render_phase(self):
         render_bootstrap = bool(self.bootstrap_image)
         render_build = not (self.last_phase == "bootstrap")
         render_final = self.last_phase in (None, "final")
-        Render = collections.namedtuple("Render", ["bootstrap", "build", "final"])
+        Render = namedtuple("Render", ["bootstrap", "build", "final"])
         return Render(bootstrap=render_bootstrap, build=render_build, final=render_final)
 
     def __call__(self):

lib/spack/spack/directory_layout.py

@@ -11,6 +11,7 @@
 import shutil
 import sys
 from contextlib import contextmanager
+from pathlib import Path
 
 import llnl.util.filesystem as fs
 import llnl.util.tty as tty
@@ -104,7 +105,7 @@ def relative_path_for_spec(self, spec):
 
         projection = spack.projections.get_projection(self.projections, spec)
         path = spec.format(projection)
-        return path
+        return str(Path(path))
 
     def write_spec(self, spec, path):
         """Write a spec out to a file."""

lib/spack/spack/environment/environment.py

@@ -1994,14 +1994,10 @@ def get_one_by_hash(self, dag_hash):
 
     def all_matching_specs(self, *specs: spack.spec.Spec) -> List[Spec]:
         """Returns all concretized specs in the environment satisfying any of the input specs"""
-        # Look up abstract hashes ahead of time, to avoid O(n^2) traversal.
-        specs = [s.lookup_hash() for s in specs]
-
-        # Avoid double lookup by directly calling _satisfies.
         return [
             s
             for s in traverse.traverse_nodes(self.concrete_roots(), key=traverse.by_dag_hash)
-            if any(s._satisfies(t) for t in specs)
+            if any(s.satisfies(t) for t in specs)
         ]
 
     @spack.repo.autospec
@@ -2448,13 +2444,13 @@ def make_repo_path(root):
 def prepare_config_scope(env):
     """Add env's scope to the global configuration search path."""
     for scope in env.config_scopes():
-        spack.config.config.push_scope(scope)
+        spack.config.CONFIG.push_scope(scope)
 
 
 def deactivate_config_scope(env):
     """Remove any scopes from env from the global config path."""
     for scope in env.config_scopes():
-        spack.config.config.remove_scope(scope.name)
+        spack.config.CONFIG.remove_scope(scope.name)
 
 
 def manifest_file(env_name_or_dir):

lib/spack/spack/main.py

@@ -602,10 +602,10 @@ def setup_main_options(args):
 
         key = syaml.syaml_str("repos")
         key.override = True
-        spack.config.config.scopes["command_line"].sections["repos"] = syaml.syaml_dict(
+        spack.config.CONFIG.scopes["command_line"].sections["repos"] = syaml.syaml_dict(
             [(key, [spack.paths.mock_packages_path])]
         )
-        spack.repo.PATH = spack.repo.create(spack.config.config)
+        spack.repo.PATH = spack.repo.create(spack.config.CONFIG)
 
     # If the user asked for it, don't check ssl certs.
     if args.insecure:
@@ -930,7 +930,7 @@ def _main(argv=None):
 
     # make spack.config aware of any command line configuration scopes
     if args.config_scopes:
-        spack.config.command_line_scopes = args.config_scopes
+        spack.config.COMMAND_LINE_SCOPES = args.config_scopes
 
     # ensure options on spack command come before everything
     setup_main_options(args)

lib/spack/spack/modules/common.py

@@ -833,7 +833,7 @@ def ensure_modules_are_enabled_or_warn():
         return
 
     # Check if we have custom TCL module sections
-    for scope in spack.config.config.file_scopes:
+    for scope in spack.config.CONFIG.file_scopes:
         # Skip default configuration
         if scope.name.startswith("default"):
             continue

lib/spack/spack/multimethod.py

@@ -236,7 +236,7 @@ def install(self, prefix):
 
         # Create a multimethod with this name if there is not one already
         original_method = MultiMethodMeta._locals.get(method.__name__)
-        if not type(original_method) == SpecMultiMethod:
+        if not isinstance(original_method, SpecMultiMethod):
             original_method = SpecMultiMethod(original_method)
 
         if self.spec is not None:

lib/spack/spack/paths.py

@@ -10,11 +10,12 @@
 dependencies.
 """
 import os
+from pathlib import PurePath
 
 import llnl.util.filesystem
 
 #: This file lives in $prefix/lib/spack/spack/__file__
-prefix = llnl.util.filesystem.ancestor(__file__, 4)
+prefix = str(PurePath(llnl.util.filesystem.ancestor(__file__, 4)))
 
 #: synonym for prefix
 spack_root = prefix
@@ -88,7 +89,7 @@ def _get_user_cache_path():
     return os.path.expanduser(os.getenv("SPACK_USER_CACHE_PATH") or "~%s.spack" % os.sep)
 
 
-user_cache_path = _get_user_cache_path()
+user_cache_path = str(PurePath(_get_user_cache_path()))
 
 #: junit, cdash, etc. reports about builds
 reports_path = os.path.join(user_cache_path, "reports")

lib/spack/spack/platforms/__init__.py

@@ -64,7 +64,7 @@ def use_platform(new_platform):
         host = _PickleableCallable(new_platform)
 
         # Clear configuration and compiler caches
-        spack.config.config.clear_caches()
+        spack.config.CONFIG.clear_caches()
         spack.compilers._cache_config_files = []
 
         yield new_platform
@@ -73,5 +73,5 @@ def use_platform(new_platform):
         host = original_host_fn
 
         # Clear configuration and compiler caches
-        spack.config.config.clear_caches()
+        spack.config.CONFIG.clear_caches()
         spack.compilers._cache_config_files = []

lib/spack/spack/repo.py

@@ -647,7 +647,7 @@ class RepoPath:
     """
 
     def __init__(self, *repos, **kwargs):
-        cache = kwargs.get("cache", spack.caches.misc_cache)
+        cache = kwargs.get("cache", spack.caches.MISC_CACHE)
         self.repos = []
         self.by_namespace = nm.NamespaceTrie()
 
@@ -966,7 +966,7 @@ def check(condition, msg):
 
         # Indexes for this repository, computed lazily
         self._repo_index = None
-        self._cache = cache or spack.caches.misc_cache
+        self._cache = cache or spack.caches.MISC_CACHE
 
     def real_name(self, import_name):
         """Allow users to import Spack packages using Python identifiers.
@@ -1357,7 +1357,7 @@ def create_or_construct(path, namespace=None):
 
 def _path(configuration=None):
     """Get the singleton RepoPath instance for Spack."""
-    configuration = configuration or spack.config.config
+    configuration = configuration or spack.config.CONFIG
     return create(configuration=configuration)
 
 
@@ -1404,14 +1404,14 @@ def use_repositories(*paths_and_repos, **kwargs):
     paths = [getattr(x, "root", x) for x in paths_and_repos]
     scope_name = "use-repo-{}".format(uuid.uuid4())
     repos_key = "repos:" if override else "repos"
-    spack.config.config.push_scope(
+    spack.config.CONFIG.push_scope(
         spack.config.InternalConfigScope(name=scope_name, data={repos_key: paths})
     )
-    PATH, saved = create(configuration=spack.config.config), PATH
+    PATH, saved = create(configuration=spack.config.CONFIG), PATH
     try:
         yield PATH
     finally:
-        spack.config.config.remove_scope(scope_name=scope_name)
+        spack.config.CONFIG.remove_scope(scope_name=scope_name)
         PATH = saved
 
 

lib/spack/spack/schema/concretizer.py

@@ -28,6 +28,12 @@
             "unify": {
                 "oneOf": [{"type": "boolean"}, {"type": "string", "enum": ["when_possible"]}]
             },
+            "duplicates": {
+                "type": "object",
+                "properties": {
+                    "strategy": {"type": "string", "enum": ["none", "minimal", "full"]}
+                },
+            },
         },
     }
 }

lib/spack/spack/solver/asp.py

@@ -8,11 +8,12 @@
 import enum
 import itertools
 import os
+import pathlib
 import pprint
 import re
 import types
 import warnings
-from typing import List
+from typing import List, NamedTuple
 
 import archspec.cpu
 
@@ -50,6 +51,8 @@
 import spack.version as vn
 import spack.version.git_ref_lookup
 
+from .counter import FullDuplicatesCounter, MinimalDuplicatesCounter, NoDuplicatesCounter
+
 # these are from clingo.ast and bootstrapped later
 ASTType = None
 parse_files = None
@@ -77,9 +80,7 @@ def default_clingo_control():
     """Return a control object with the default settings used in Spack"""
     control = clingo.Control()
     control.configuration.configuration = "tweety"
-    control.configuration.solve.models = 0
     control.configuration.solver.heuristic = "Domain"
-    control.configuration.solve.parallel_mode = "1"
     control.configuration.solver.opt_strategy = "usc,one"
     return control
 
@@ -266,12 +267,14 @@ def _id(thing):
 
 @llnl.util.lang.key_ordering
 class AspFunction(AspObject):
+    __slots__ = ["name", "args"]
+
     def __init__(self, name, args=None):
         self.name = name
         self.args = () if args is None else tuple(args)
 
     def _cmp_key(self):
-        return (self.name, self.args)
+        return self.name, self.args
 
     def __call__(self, *args):
         """Return a new instance of this function with added arguments.
@@ -302,6 +305,8 @@ def argify(arg):
                 return clingo.String(str(arg))
             elif isinstance(arg, int):
                 return clingo.Number(arg)
+            elif isinstance(arg, AspFunction):
+                return clingo.Function(arg.name, [argify(x) for x in arg.args], positive=positive)
             else:
                 return clingo.String(str(arg))
 
@@ -322,6 +327,15 @@ def __getattr__(self, name):
 fn = AspFunctionBuilder()
 
 
+def _create_counter(specs, tests):
+    strategy = spack.config.CONFIG.get("concretizer:duplicates:strategy", "none")
+    if strategy == "full":
+        return FullDuplicatesCounter(specs, tests=tests)
+    if strategy == "minimal":
+        return MinimalDuplicatesCounter(specs, tests=tests)
+    return NoDuplicatesCounter(specs, tests=tests)
+
+
 def all_compilers_in_config():
     return spack.compilers.all_compilers()
 
@@ -513,15 +527,17 @@ def _compute_specs_from_answer_set(self):
         best = min(self.answers)
         opt, _, answer = best
         for input_spec in self.abstract_specs:
-            key = input_spec.name
+            node = SpecBuilder.make_node(pkg=input_spec.name)
             if input_spec.virtual:
-                providers = [spec.name for spec in answer.values() if spec.package.provides(key)]
-                key = providers[0]
-            candidate = answer.get(key)
+                providers = [
+                    spec.name for spec in answer.values() if spec.package.provides(input_spec.name)
+                ]
+                node = SpecBuilder.make_node(pkg=providers[0])
+            candidate = answer.get(node)
 
             if candidate and candidate.satisfies(input_spec):
-                self._concrete_specs.append(answer[key])
-                self._concrete_specs_by_input[input_spec] = answer[key]
+                self._concrete_specs.append(answer[node])
+                self._concrete_specs_by_input[input_spec] = answer[node]
             else:
                 self._unsolved_specs.append(input_spec)
 
@@ -572,16 +588,33 @@ def bootstrap_clingo():
         from clingo import parse_files
 
 
-def stringify(sym):
-    """Stringify symbols from clingo models.
+class NodeArgument(NamedTuple):
+    id: str
+    pkg: str
 
-    This will turn a ``clingo.Symbol`` into a string, or a sequence of ``clingo.Symbol``
-    objects into a tuple of strings.
 
+def intermediate_repr(sym):
+    """Returns an intermediate representation of clingo models for Spack's spec builder.
+
+    Currently, transforms symbols from clingo models either to strings or to NodeArgument objects.
+
+    Returns:
+        This will turn a ``clingo.Symbol`` into a string or NodeArgument, or a sequence of
+        ``clingo.Symbol`` objects into a tuple of those objects.
     """
     # TODO: simplify this when we no longer have to support older clingo versions.
     if isinstance(sym, (list, tuple)):
-        return tuple(stringify(a) for a in sym)
+        return tuple(intermediate_repr(a) for a in sym)
+
+    try:
+        if sym.name == "node":
+            return NodeArgument(
+                id=intermediate_repr(sym.arguments[0]), pkg=intermediate_repr(sym.arguments[1])
+            )
+    except RuntimeError:
+        # This happens when using clingo w/ CFFI and trying to access ".name" for symbols
+        # that are not functions
+        pass
 
     if clingo_cffi:
         # Clingo w/ CFFI will throw an exception on failure
@@ -596,10 +629,10 @@ def stringify(sym):
 def extract_args(model, predicate_name):
     """Extract the arguments to predicates with the provided name from a model.
 
-    Pull out all the predicates with name ``predicate_name`` from the model, and return
-    their stringified arguments as tuples.
+    Pull out all the predicates with name ``predicate_name`` from the model, and
+    return their intermediate representation.
     """
-    return [stringify(sym.arguments) for sym in model if sym.name == predicate_name]
+    return [intermediate_repr(sym.arguments) for sym in model if sym.name == predicate_name]
 
 
 class ErrorHandler:
@@ -700,7 +733,9 @@ def fact(self, head):
         """
         symbol = head.symbol() if hasattr(head, "symbol") else head
 
-        self.out.write("%s.\n" % str(symbol))
+        # This is commented out to avoid evaluating str(symbol) when we have no stream
+        if not isinstance(self.out, llnl.util.lang.Devnull):
+            self.out.write(f"{str(symbol)}.\n")
 
         atom = self.backend.add_atom(symbol)
 
@@ -772,8 +807,11 @@ def visit(node):
 
         # Load the file itself
         self.control.load(os.path.join(parent_dir, "concretize.lp"))
+        self.control.load(os.path.join(parent_dir, "heuristic.lp"))
         self.control.load(os.path.join(parent_dir, "os_compatibility.lp"))
         self.control.load(os.path.join(parent_dir, "display.lp"))
+        if not setup.concretize_everything:
+            self.control.load(os.path.join(parent_dir, "when_possible.lp"))
         timer.stop("load")
 
         # Grounding is the first step in the solve -- it turns our facts
@@ -801,6 +839,14 @@ def on_model(model):
 
         timer.start("solve")
         solve_result = self.control.solve(**solve_kwargs)
+
+        if solve_result.satisfiable and self._model_has_cycles(models):
+            tty.debug(f"cycles detected, falling back to slower algorithm [specs={specs}]")
+            self.control.load(os.path.join(parent_dir, "cycle_detection.lp"))
+            self.control.ground([("no_cycle", [])])
+            models.clear()
+            solve_result = self.control.solve(**solve_kwargs)
+
         timer.stop("solve")
 
         # once done, construct the solve result
@@ -836,7 +882,8 @@ def on_model(model):
             for sym in best_model:
                 if sym.name not in ("attr", "error", "opt_criterion"):
                     tty.debug(
-                        "UNKNOWN SYMBOL: %s(%s)" % (sym.name, ", ".join(stringify(sym.arguments)))
+                        "UNKNOWN SYMBOL: %s(%s)"
+                        % (sym.name, ", ".join(intermediate_repr(sym.arguments)))
                     )
 
         elif cores:
@@ -853,6 +900,26 @@ def on_model(model):
 
         return result, timer, self.control.statistics
 
+    def _model_has_cycles(self, models):
+        """Returns true if the best model has cycles in it"""
+        cycle_detection = clingo.Control()
+        parent_dir = pathlib.Path(__file__).parent
+        lp_file = parent_dir / "cycle_detection.lp"
+
+        min_cost, best_model = min(models)
+        with cycle_detection.backend() as backend:
+            for atom in best_model:
+                if atom.name == "attr" and str(atom.arguments[0]) == '"depends_on"':
+                    symbol = fn.depends_on(atom.arguments[1], atom.arguments[2])
+                    atom_id = backend.add_atom(symbol.symbol())
+                    backend.add_rule([atom_id], [], choice=False)
+
+            cycle_detection.load(str(lp_file))
+            cycle_detection.ground([("base", []), ("no_cycle", [])])
+            cycle_result = cycle_detection.solve()
+
+        return cycle_result.unsatisfiable
+
 
 class SpackSolverSetup:
     """Class to set up and run a Spack concretization solve."""
@@ -883,6 +950,10 @@ def __init__(self, tests=False):
 
         # id for dummy variables
         self._condition_id_counter = itertools.count()
+        self._trigger_id_counter = itertools.count()
+        self._trigger_cache = collections.defaultdict(dict)
+        self._effect_id_counter = itertools.count()
+        self._effect_cache = collections.defaultdict(dict)
 
         # Caches to optimize the setup phase of the solver
         self.target_specs_cache = None
@@ -919,15 +990,18 @@ def key_fn(version):
 
         for weight, declared_version in enumerate(most_to_least_preferred):
             self.gen.fact(
-                fn.version_declared(
-                    pkg.name, declared_version.version, weight, str(declared_version.origin)
+                fn.pkg_fact(
+                    pkg.name,
+                    fn.version_declared(
+                        declared_version.version, weight, str(declared_version.origin)
+                    ),
                 )
             )
 
         # Declare deprecated versions for this package, if any
         deprecated = self.deprecated_versions[pkg.name]
         for v in sorted(deprecated):
-            self.gen.fact(fn.deprecated_version(pkg.name, v))
+            self.gen.fact(fn.pkg_fact(pkg.name, fn.deprecated_version(v)))
 
     def spec_versions(self, spec):
         """Return list of clauses expressing spec's version constraints."""
@@ -960,7 +1034,10 @@ def conflict_rules(self, pkg):
         no_constraint_msg = "{0}: conflicts with '{1}'"
         for trigger, constraints in pkg.conflicts.items():
             trigger_msg = "conflict trigger %s" % str(trigger)
-            trigger_id = self.condition(spack.spec.Spec(trigger), name=pkg.name, msg=trigger_msg)
+            trigger_spec = spack.spec.Spec(trigger)
+            trigger_id = self.condition(
+                trigger_spec, name=trigger_spec.name or pkg.name, msg=trigger_msg
+            )
 
             for constraint, conflict_msg in constraints:
                 if conflict_msg is None:
@@ -970,7 +1047,9 @@ def conflict_rules(self, pkg):
                         conflict_msg = default_msg.format(pkg.name, trigger, constraint)
                 constraint_msg = "conflict constraint %s" % str(constraint)
                 constraint_id = self.condition(constraint, name=pkg.name, msg=constraint_msg)
-                self.gen.fact(fn.conflict(pkg.name, trigger_id, constraint_id, conflict_msg))
+                self.gen.fact(
+                    fn.pkg_fact(pkg.name, fn.conflict(trigger_id, constraint_id, conflict_msg))
+                )
                 self.gen.newline()
 
     def compiler_facts(self):
@@ -1023,8 +1102,11 @@ def package_compiler_defaults(self, pkg):
 
         for i, compiler in enumerate(reversed(matches)):
             self.gen.fact(
-                fn.node_compiler_preference(
-                    pkg.name, compiler.spec.name, compiler.spec.version, -i * 100
+                fn.pkg_fact(
+                    pkg.name,
+                    fn.node_compiler_preference(
+                        compiler.spec.name, compiler.spec.version, -i * 100
+                    ),
                 )
             )
 
@@ -1114,12 +1196,65 @@ def pkg_rules(self, pkg, tests):
         self.gen.newline()
 
         # variants
+        self.variant_rules(pkg)
+
+        # conflicts
+        self.conflict_rules(pkg)
+
+        # default compilers for this package
+        self.package_compiler_defaults(pkg)
+
+        # virtuals
+        self.package_provider_rules(pkg)
+
+        # dependencies
+        self.package_dependencies_rules(pkg)
+
+        # virtual preferences
+        self.virtual_preferences(
+            pkg.name,
+            lambda v, p, i: self.gen.fact(fn.pkg_fact(pkg.name, fn.provider_preference(v, p, i))),
+        )
+
+        self.package_requirement_rules(pkg)
+
+        # trigger and effect tables
+        self.trigger_rules()
+        self.effect_rules()
+
+    def trigger_rules(self):
+        """Flushes all the trigger rules collected so far, and clears the cache."""
+        self.gen.h2("Trigger conditions")
+        for name in self._trigger_cache:
+            cache = self._trigger_cache[name]
+            for spec_str, (trigger_id, requirements) in cache.items():
+                self.gen.fact(fn.pkg_fact(name, fn.trigger_id(trigger_id)))
+                self.gen.fact(fn.pkg_fact(name, fn.trigger_msg(spec_str)))
+                for predicate in requirements:
+                    self.gen.fact(fn.condition_requirement(trigger_id, *predicate.args))
+                self.gen.newline()
+        self._trigger_cache.clear()
+
+    def effect_rules(self):
+        """Flushes all the effect rules collected so far, and clears the cache."""
+        self.gen.h2("Imposed requirements")
+        for name in self._effect_cache:
+            cache = self._effect_cache[name]
+            for spec_str, (effect_id, requirements) in cache.items():
+                self.gen.fact(fn.pkg_fact(name, fn.effect_id(effect_id)))
+                self.gen.fact(fn.pkg_fact(name, fn.effect_msg(spec_str)))
+                for predicate in requirements:
+                    self.gen.fact(fn.imposed_constraint(effect_id, *predicate.args))
+                self.gen.newline()
+        self._effect_cache.clear()
+
+    def variant_rules(self, pkg):
         for name, entry in sorted(pkg.variants.items()):
             variant, when = entry
 
             if spack.spec.Spec() in when:
                 # unconditional variant
-                self.gen.fact(fn.variant(pkg.name, name))
+                self.gen.fact(fn.pkg_fact(pkg.name, fn.variant(name)))
             else:
                 # conditional variant
                 for w in when:
@@ -1128,19 +1263,23 @@ def pkg_rules(self, pkg, tests):
                         msg += " when %s" % w
 
                     cond_id = self.condition(w, name=pkg.name, msg=msg)
-                    self.gen.fact(fn.variant_condition(cond_id, pkg.name, name))
+                    self.gen.fact(fn.pkg_fact(pkg.name, fn.conditional_variant(cond_id, name)))
 
             single_value = not variant.multi
             if single_value:
-                self.gen.fact(fn.variant_single_value(pkg.name, name))
+                self.gen.fact(fn.pkg_fact(pkg.name, fn.variant_single_value(name)))
                 self.gen.fact(
-                    fn.variant_default_value_from_package_py(pkg.name, name, variant.default)
+                    fn.pkg_fact(
+                        pkg.name, fn.variant_default_value_from_package_py(name, variant.default)
+                    )
                 )
             else:
                 spec_variant = variant.make_default()
                 defaults = spec_variant.value
                 for val in sorted(defaults):
-                    self.gen.fact(fn.variant_default_value_from_package_py(pkg.name, name, val))
+                    self.gen.fact(
+                        fn.pkg_fact(pkg.name, fn.variant_default_value_from_package_py(name, val))
+                    )
 
             values = variant.values
             if values is None:
@@ -1151,7 +1290,9 @@ def pkg_rules(self, pkg, tests):
                 for sid, s in enumerate(values.sets):
                     for value in s:
                         self.gen.fact(
-                            fn.variant_value_from_disjoint_sets(pkg.name, name, value, sid)
+                            fn.pkg_fact(
+                                pkg.name, fn.variant_value_from_disjoint_sets(name, value, sid)
+                            )
                         )
                     union.update(s)
                 values = union
@@ -1178,7 +1319,9 @@ def pkg_rules(self, pkg, tests):
                             msg="empty (total) conflict constraint",
                         )
                         msg = "variant {0}={1} is conditionally disabled".format(name, value)
-                        self.gen.fact(fn.conflict(pkg.name, trigger_id, constraint_id, msg))
+                        self.gen.fact(
+                            fn.pkg_fact(pkg.name, fn.conflict(trigger_id, constraint_id, msg))
+                        )
                     else:
                         imposed = spack.spec.Spec(value.when)
                         imposed.name = pkg.name
@@ -1189,32 +1332,13 @@ def pkg_rules(self, pkg, tests):
                             name=pkg.name,
                             msg="%s variant %s value %s when %s" % (pkg.name, name, value, when),
                         )
-                self.gen.fact(fn.variant_possible_value(pkg.name, name, value))
+                self.gen.fact(fn.pkg_fact(pkg.name, fn.variant_possible_value(name, value)))
 
             if variant.sticky:
-                self.gen.fact(fn.variant_sticky(pkg.name, name))
+                self.gen.fact(fn.pkg_fact(pkg.name, fn.variant_sticky(name)))
 
             self.gen.newline()
 
-        # conflicts
-        self.conflict_rules(pkg)
-
-        # default compilers for this package
-        self.package_compiler_defaults(pkg)
-
-        # virtuals
-        self.package_provider_rules(pkg)
-
-        # dependencies
-        self.package_dependencies_rules(pkg)
-
-        # virtual preferences
-        self.virtual_preferences(
-            pkg.name, lambda v, p, i: self.gen.fact(fn.pkg_provider_preference(pkg.name, v, p, i))
-        )
-
-        self.package_requirement_rules(pkg)
-
     def condition(self, required_spec, imposed_spec=None, name=None, msg=None, node=False):
         """Generate facts for a dependency or virtual provider condition.
 
@@ -1232,21 +1356,41 @@ def condition(self, required_spec, imposed_spec=None, name=None, msg=None, node=
         """
         named_cond = required_spec.copy()
         named_cond.name = named_cond.name or name
-        assert named_cond.name, "must provide name for anonymous condtions!"
+        assert named_cond.name, "must provide name for anonymous conditions!"
 
         # Check if we can emit the requirements before updating the condition ID counter.
         # In this way, if a condition can't be emitted but the exception is handled in the caller,
         # we won't emit partial facts.
-        requirements = self.spec_clauses(named_cond, body=True, required_from=name)
 
         condition_id = next(self._condition_id_counter)
-        self.gen.fact(fn.condition(condition_id, msg))
-        for pred in requirements:
-            self.gen.fact(fn.condition_requirement(condition_id, *pred.args))
+        self.gen.fact(fn.pkg_fact(named_cond.name, fn.condition(condition_id)))
+        self.gen.fact(fn.condition_reason(condition_id, msg))
 
-        if imposed_spec:
-            self.impose(condition_id, imposed_spec, node=node, name=name)
+        cache = self._trigger_cache[named_cond.name]
 
+        named_cond_key = str(named_cond)
+        if named_cond_key not in cache:
+            trigger_id = next(self._trigger_id_counter)
+            requirements = self.spec_clauses(named_cond, body=True, required_from=name)
+            cache[named_cond_key] = (trigger_id, requirements)
+        trigger_id, requirements = cache[named_cond_key]
+        self.gen.fact(fn.pkg_fact(named_cond.name, fn.condition_trigger(condition_id, trigger_id)))
+
+        if not imposed_spec:
+            return condition_id
+
+        cache = self._effect_cache[named_cond.name]
+        imposed_spec_key = str(imposed_spec)
+        if imposed_spec_key not in cache:
+            effect_id = next(self._effect_id_counter)
+            requirements = self.spec_clauses(imposed_spec, body=False, required_from=name)
+            if not node:
+                requirements = list(
+                    filter(lambda x: x.args[0] not in ("node", "virtual_node"), requirements)
+                )
+            cache[imposed_spec_key] = (effect_id, requirements)
+        effect_id, requirements = cache[imposed_spec_key]
+        self.gen.fact(fn.pkg_fact(named_cond.name, fn.condition_effect(condition_id, effect_id)))
         return condition_id
 
     def impose(self, condition_id, imposed_spec, node=True, name=None, body=False):
@@ -1259,13 +1403,19 @@ def impose(self, condition_id, imposed_spec, node=True, name=None, body=False):
 
     def package_provider_rules(self, pkg):
         for provider_name in sorted(set(s.name for s in pkg.provided.keys())):
-            self.gen.fact(fn.possible_provider(pkg.name, provider_name))
+            if provider_name not in self.possible_virtuals:
+                continue
+            self.gen.fact(fn.pkg_fact(pkg.name, fn.possible_provider(provider_name)))
 
         for provided, whens in pkg.provided.items():
+            if provided.name not in self.possible_virtuals:
+                continue
             for when in whens:
                 msg = "%s provides %s when %s" % (pkg.name, provided, when)
                 condition_id = self.condition(when, provided, pkg.name, msg)
-                self.gen.fact(fn.provider_condition(condition_id, when.name, provided.name))
+                self.gen.fact(
+                    fn.pkg_fact(when.name, fn.provider_condition(condition_id, provided.name))
+                )
             self.gen.newline()
 
     def package_dependencies_rules(self, pkg):
@@ -1289,9 +1439,13 @@ def package_dependencies_rules(self, pkg):
                 msg = "%s depends on %s" % (pkg.name, dep.spec.name)
                 if cond != spack.spec.Spec():
                     msg += " when %s" % cond
+                else:
+                    pass
 
                 condition_id = self.condition(cond, dep.spec, pkg.name, msg)
-                self.gen.fact(fn.dependency_condition(condition_id, pkg.name, dep.spec.name))
+                self.gen.fact(
+                    fn.pkg_fact(pkg.name, fn.dependency_condition(condition_id, dep.spec.name))
+                )
 
                 for t in sorted(deptypes):
                     # there is a declared dependency of type t
@@ -1328,7 +1482,7 @@ def provider_requirements(self):
             "Internal Error: possible_virtuals is not populated. Please report to the spack"
             " maintainers"
         )
-        packages_yaml = spack.config.config.get("packages")
+        packages_yaml = spack.config.CONFIG.get("packages")
         assert self.possible_virtuals is not None, msg
         for virtual_str in sorted(self.possible_virtuals):
             requirements = packages_yaml.get(virtual_str, {}).get("require", [])
@@ -1336,6 +1490,8 @@ def provider_requirements(self):
                 virtual_str, requirements, kind=RequirementKind.VIRTUAL
             )
             self.emit_facts_from_requirement_rules(rules)
+            self.trigger_rules()
+            self.effect_rules()
 
     def emit_facts_from_requirement_rules(self, rules: List[RequirementRule]):
         """Generate facts to enforce requirements.
@@ -1449,10 +1605,12 @@ def external_packages(self):
             for local_idx, spec in enumerate(external_specs):
                 msg = "%s available as external when satisfying %s" % (spec.name, spec)
                 condition_id = self.condition(spec, msg=msg)
-                self.gen.fact(fn.possible_external(condition_id, pkg_name, local_idx))
+                self.gen.fact(fn.pkg_fact(pkg_name, fn.possible_external(condition_id, local_idx)))
                 self.possible_versions[spec.name].add(spec.version)
                 self.gen.newline()
 
+            self.trigger_rules()
+
     def preferred_variants(self, pkg_name):
         """Facts on concretization preferences, as read from packages.yaml"""
         preferences = spack.package_prefs.PackagePrefs
@@ -1495,7 +1653,9 @@ def target_preferences(self, pkg_name):
             if str(preferred.architecture.target) == best_default and i != 0:
                 offset = 100
             self.gen.fact(
-                fn.target_weight(pkg_name, str(preferred.architecture.target), i + offset)
+                fn.pkg_fact(
+                    pkg_name, fn.target_weight(str(preferred.architecture.target), i + offset)
+                )
             )
 
     def spec_clauses(self, *args, **kwargs):
@@ -2041,11 +2201,11 @@ def define_version_constraints(self):
             # generate facts for each package constraint and the version
             # that satisfies it
             for v in sorted(v for v in self.possible_versions[pkg_name] if v.satisfies(versions)):
-                self.gen.fact(fn.version_satisfies(pkg_name, versions, v))
+                self.gen.fact(fn.pkg_fact(pkg_name, fn.version_satisfies(versions, v)))
 
             self.gen.newline()
 
-    def define_virtual_constraints(self):
+    def collect_virtual_constraints(self):
         """Define versions for constraints on virtuals.
 
         Must be called before define_version_constraints().
@@ -2131,7 +2291,7 @@ def define_variant_values(self):
         # spec_clauses(). We might want to order these facts by pkg and name
         # if we are debugging.
         for pkg, variant, value in self.variant_values_from_specs:
-            self.gen.fact(fn.variant_possible_value(pkg, variant, value))
+            self.gen.fact(fn.pkg_fact(pkg, fn.variant_possible_value(variant, value)))
 
     def _facts_from_concrete_spec(self, spec, possible):
         # tell the solver about any installed packages that could
@@ -2191,20 +2351,19 @@ def setup(self, driver, specs, reuse=None):
 
         # get list of all possible dependencies
         self.possible_virtuals = set(x.name for x in specs if x.virtual)
-        possible = spack.package_base.possible_dependencies(
-            *specs, virtuals=self.possible_virtuals, deptype=spack.dependency.all_deptypes
-        )
+
+        node_counter = _create_counter(specs, tests=self.tests)
+        self.possible_virtuals = node_counter.possible_virtuals()
+        self.pkgs = node_counter.possible_dependencies()
 
         # Fail if we already know an unreachable node is requested
         for spec in specs:
             missing_deps = [
-                str(d) for d in spec.traverse() if d.name not in possible and not d.virtual
+                str(d) for d in spec.traverse() if d.name not in self.pkgs and not d.virtual
             ]
             if missing_deps:
                 raise spack.spec.InvalidDependencyError(spec.name, missing_deps)
 
-        self.pkgs = set(possible)
-
         # driver is used by all the functions below to add facts and
         # rules to generate an ASP program.
         self.gen = driver
@@ -2228,13 +2387,16 @@ def setup(self, driver, specs, reuse=None):
         self.possible_compilers = self.generate_possible_compilers(specs)
 
         self.gen.h1("Concrete input spec definitions")
-        self.define_concrete_input_specs(specs, possible)
+        self.define_concrete_input_specs(specs, self.pkgs)
 
         if reuse:
             self.gen.h1("Reusable specs")
             self.gen.fact(fn.optimize_for_reuse())
             for reusable_spec in reuse:
-                self._facts_from_concrete_spec(reusable_spec, possible)
+                self._facts_from_concrete_spec(reusable_spec, self.pkgs)
+
+        self.gen.h1("Generic statements on possible packages")
+        node_counter.possible_packages_facts(self.gen, fn)
 
         self.gen.h1("Possible flags on nodes")
         for flag in spack.spec.FlagMap.valid_compiler_flags():
@@ -2255,7 +2417,7 @@ def setup(self, driver, specs, reuse=None):
         self.external_packages()
 
         # traverse all specs and packages to build dict of possible versions
-        self.build_version_dict(possible)
+        self.build_version_dict(self.pkgs)
         self.add_concrete_versions_from_specs(specs, Provenance.SPEC)
         self.add_concrete_versions_from_specs(dev_specs, Provenance.DEV_SPEC)
 
@@ -2270,9 +2432,12 @@ def setup(self, driver, specs, reuse=None):
             self.preferred_variants(pkg)
             self.target_preferences(pkg)
 
+        self.gen.h1("Develop specs")
         # Inject dev_path from environment
         for ds in dev_specs:
             self.condition(spack.spec.Spec(ds.name), ds, msg="%s is a develop spec" % ds.name)
+            self.trigger_rules()
+            self.effect_rules()
 
         self.gen.h1("Spec Constraints")
         self.literal_specs(specs)
@@ -2280,10 +2445,8 @@ def setup(self, driver, specs, reuse=None):
         self.gen.h1("Variant Values defined in specs")
         self.define_variant_values()
 
-        self.gen.h1("Virtual Constraints")
-        self.define_virtual_constraints()
-
         self.gen.h1("Version Constraints")
+        self.collect_virtual_constraints()
         self.define_version_constraints()
 
         self.gen.h1("Compiler Version Constraints")
@@ -2305,8 +2468,8 @@ def literal_specs(self, specs):
                         fn.literal(idx, "variant_default_value_from_cli", *clause.args[1:])
                     )
 
-        if self.concretize_everything:
-            self.gen.fact(fn.concretize_everything())
+            if self.concretize_everything:
+                self.gen.fact(fn.solve_literal(idx))
 
     def _get_versioned_specs_from_pkg_requirements(self):
         """If package requirements mention versions that are not mentioned
@@ -2401,6 +2564,16 @@ class SpecBuilder:
         )
     )
 
+    @staticmethod
+    def make_node(*, pkg: str) -> NodeArgument:
+        """Given a package name, returns the string representation of the "min_dupe_id" node in
+        the ASP encoding.
+
+        Args:
+            pkg: name of a package
+        """
+        return NodeArgument(id="0", pkg=pkg)
+
     def __init__(self, specs, hash_lookup=None):
         self._specs = {}
         self._result = None
@@ -2413,101 +2586,105 @@ def __init__(self, specs, hash_lookup=None):
         # from this dictionary during reconstruction
         self._hash_lookup = hash_lookup or {}
 
-    def hash(self, pkg, h):
-        if pkg not in self._specs:
-            self._specs[pkg] = self._hash_lookup[h]
-        self._hash_specs.append(pkg)
+    def hash(self, node, h):
+        if node not in self._specs:
+            self._specs[node] = self._hash_lookup[h]
+        self._hash_specs.append(node)
 
-    def node(self, pkg):
-        if pkg not in self._specs:
-            self._specs[pkg] = spack.spec.Spec(pkg)
+    def node(self, node):
+        if node not in self._specs:
+            self._specs[node] = spack.spec.Spec(node.pkg)
 
-    def _arch(self, pkg):
-        arch = self._specs[pkg].architecture
+    def _arch(self, node):
+        arch = self._specs[node].architecture
         if not arch:
             arch = spack.spec.ArchSpec()
-            self._specs[pkg].architecture = arch
+            self._specs[node].architecture = arch
         return arch
 
-    def node_platform(self, pkg, platform):
-        self._arch(pkg).platform = platform
+    def node_platform(self, node, platform):
+        self._arch(node).platform = platform
 
-    def node_os(self, pkg, os):
-        self._arch(pkg).os = os
+    def node_os(self, node, os):
+        self._arch(node).os = os
 
-    def node_target(self, pkg, target):
-        self._arch(pkg).target = target
+    def node_target(self, node, target):
+        self._arch(node).target = target
 
-    def variant_value(self, pkg, name, value):
+    def variant_value(self, node, name, value):
         # FIXME: is there a way not to special case 'dev_path' everywhere?
         if name == "dev_path":
-            self._specs[pkg].variants.setdefault(
+            self._specs[node].variants.setdefault(
                 name, spack.variant.SingleValuedVariant(name, value)
             )
             return
 
         if name == "patches":
-            self._specs[pkg].variants.setdefault(
+            self._specs[node].variants.setdefault(
                 name, spack.variant.MultiValuedVariant(name, value)
             )
             return
 
-        self._specs[pkg].update_variant_validate(name, value)
+        self._specs[node].update_variant_validate(name, value)
 
-    def version(self, pkg, version):
-        self._specs[pkg].versions = vn.VersionList([vn.Version(version)])
+    def version(self, node, version):
+        self._specs[node].versions = vn.VersionList([vn.Version(version)])
 
-    def node_compiler_version(self, pkg, compiler, version):
-        self._specs[pkg].compiler = spack.spec.CompilerSpec(compiler)
-        self._specs[pkg].compiler.versions = vn.VersionList([vn.Version(version)])
+    def node_compiler_version(self, node, compiler, version):
+        self._specs[node].compiler = spack.spec.CompilerSpec(compiler)
+        self._specs[node].compiler.versions = vn.VersionList([vn.Version(version)])
 
-    def node_flag_compiler_default(self, pkg):
-        self._flag_compiler_defaults.add(pkg)
+    def node_flag_compiler_default(self, node):
+        self._flag_compiler_defaults.add(node)
 
-    def node_flag(self, pkg, flag_type, flag):
-        self._specs[pkg].compiler_flags.add_flag(flag_type, flag, False)
+    def node_flag(self, node, flag_type, flag):
+        self._specs[node].compiler_flags.add_flag(flag_type, flag, False)
 
-    def node_flag_source(self, pkg, flag_type, source):
-        self._flag_sources[(pkg, flag_type)].add(source)
+    def node_flag_source(self, node, flag_type, source):
+        self._flag_sources[(node, flag_type)].add(source)
 
-    def no_flags(self, pkg, flag_type):
-        self._specs[pkg].compiler_flags[flag_type] = []
+    def no_flags(self, node, flag_type):
+        self._specs[node].compiler_flags[flag_type] = []
 
-    def external_spec_selected(self, pkg, idx):
+    def external_spec_selected(self, node, idx):
         """This means that the external spec and index idx
         has been selected for this package.
         """
+
         packages_yaml = spack.config.get("packages")
         packages_yaml = _normalize_packages_yaml(packages_yaml)
-        spec_info = packages_yaml[pkg]["externals"][int(idx)]
-        self._specs[pkg].external_path = spec_info.get("prefix", None)
-        self._specs[pkg].external_modules = spack.spec.Spec._format_module_list(
+        spec_info = packages_yaml[node.pkg]["externals"][int(idx)]
+        self._specs[node].external_path = spec_info.get("prefix", None)
+        self._specs[node].external_modules = spack.spec.Spec._format_module_list(
             spec_info.get("modules", None)
         )
-        self._specs[pkg].extra_attributes = spec_info.get("extra_attributes", {})
+        self._specs[node].extra_attributes = spec_info.get("extra_attributes", {})
 
         # If this is an extension, update the dependencies to include the extendee
-        package = self._specs[pkg].package_class(self._specs[pkg])
+        package = self._specs[node].package_class(self._specs[node])
         extendee_spec = package.extendee_spec
+
         if extendee_spec:
-            package.update_external_dependencies(self._specs.get(extendee_spec.name, None))
+            extendee_node = SpecBuilder.make_node(pkg=extendee_spec.name)
+            package.update_external_dependencies(self._specs.get(extendee_node, None))
 
-    def depends_on(self, pkg, dep, type):
-        dependencies = self._specs[pkg].edges_to_dependencies(name=dep)
+    def depends_on(self, parent_node, dependency_node, type):
+        dependency_spec = self._specs[dependency_node]
+        edges = self._specs[parent_node].edges_to_dependencies(name=dependency_spec.name)
+        edges = [x for x in edges if id(x.spec) == id(dependency_spec)]
 
-        # TODO: assertion to be removed when cross-compilation is handled correctly
-        msg = "Current solver does not handle multiple dependency edges of the same name"
-        assert len(dependencies) < 2, msg
-
-        if not dependencies:
-            self._specs[pkg].add_dependency_edge(self._specs[dep], deptypes=(type,), virtuals=())
+        if not edges:
+            self._specs[parent_node].add_dependency_edge(
+                self._specs[dependency_node], deptypes=(type,), virtuals=()
+            )
         else:
-            # TODO: This assumes that each solve unifies dependencies
-            dependencies[0].update_deptypes(deptypes=(type,))
+            edges[0].update_deptypes(deptypes=(type,))
 
-    def virtual_on_edge(self, pkg, provider, virtual):
-        dependencies = self._specs[pkg].edges_to_dependencies(name=provider)
-        assert len(dependencies) == 1
+    def virtual_on_edge(self, parent_node, provider_node, virtual):
+        dependencies = self._specs[parent_node].edges_to_dependencies(name=(provider_node.pkg))
+        provider_spec = self._specs[provider_node]
+        dependencies = [x for x in dependencies if id(x.spec) == id(provider_spec)]
+        assert len(dependencies) == 1, f"{virtual}: {provider_node.pkg}"
         dependencies[0].update_virtuals((virtual,))
 
     def reorder_flags(self):
@@ -2537,19 +2714,23 @@ def reorder_flags(self):
 
                 # order is determined by the  DAG. A spec's flags come after any of its ancestors
                 # on the compile line
-                source_key = (spec.name, flag_type)
+                node = SpecBuilder.make_node(pkg=spec.name)
+                source_key = (node, flag_type)
                 if source_key in self._flag_sources:
-                    order = [s.name for s in spec.traverse(order="post", direction="parents")]
+                    order = [
+                        SpecBuilder.make_node(pkg=s.name)
+                        for s in spec.traverse(order="post", direction="parents")
+                    ]
                     sorted_sources = sorted(
                         self._flag_sources[source_key], key=lambda s: order.index(s)
                     )
 
                     # add flags from each source, lowest to highest precedence
-                    for name in sorted_sources:
+                    for node in sorted_sources:
                         all_src_flags = list()
-                        per_pkg_sources = [self._specs[name]]
-                        if name in cmd_specs:
-                            per_pkg_sources.append(cmd_specs[name])
+                        per_pkg_sources = [self._specs[node]]
+                        if node.pkg in cmd_specs:
+                            per_pkg_sources.append(cmd_specs[node.pkg])
                         for source in per_pkg_sources:
                             all_src_flags.extend(source.compiler_flags.get(flag_type, []))
                         extend_flag_list(from_sources, all_src_flags)
@@ -2620,14 +2801,15 @@ def build_specs(self, function_tuples):
             # solving but don't construct anything. Do not ignore error
             # predicates on virtual packages.
             if name != "error":
-                pkg = args[0]
+                node = args[0]
+                pkg = node.pkg
                 if spack.repo.PATH.is_virtual(pkg):
                     continue
 
                 # if we've already gotten a concrete spec for this pkg,
                 # do not bother calling actions on it except for node_flag_source,
                 # since node_flag_source is tracking information not in the spec itself
-                spec = self._specs.get(pkg)
+                spec = self._specs.get(args[0])
                 if spec and spec.concrete:
                     if name != "node_flag_source":
                         continue
@@ -2645,10 +2827,12 @@ def build_specs(self, function_tuples):
         # fix flags after all specs are constructed
         self.reorder_flags()
 
+        # cycle detection
+        roots = [spec.root for spec in self._specs.values() if not spec.root.installed]
+
         # inject patches -- note that we' can't use set() to unique the
         # roots here, because the specs aren't complete, and the hash
         # function will loop forever.
-        roots = [spec.root for spec in self._specs.values() if not spec.root.installed]
         roots = dict((id(r), r) for r in roots)
         for root in roots.values():
             spack.spec.Spec.inject_patches_variant(root)
@@ -2768,7 +2952,7 @@ def solve(self, specs, out=None, timers=False, stats=False, tests=False, setup_o
         Arguments:
           specs (list): List of ``Spec`` objects to solve for.
           out: Optionally write the generate ASP program to a file-like object.
-          timers (bool): Print out coarse fimers for different solve phases.
+          timers (bool): Print out coarse timers for different solve phases.
           stats (bool): Print out detailed stats from clingo.
           tests (bool or tuple): If True, concretize test dependencies for all packages.
             If a tuple of package names, concretize test dependencies for named
@@ -2776,6 +2960,7 @@ def solve(self, specs, out=None, timers=False, stats=False, tests=False, setup_o
           setup_only (bool): if True, stop after setup and don't solve (default False).
         """
         # Check upfront that the variants are admissible
+        specs = [s.lookup_hash() for s in specs]
         reusable_specs = self._check_input_and_extract_concrete_specs(specs)
         reusable_specs.extend(self._reusable_specs(specs))
         setup = SpackSolverSetup(tests=tests)
@@ -2799,6 +2984,7 @@ def solve_in_rounds(self, specs, out=None, timers=False, stats=False, tests=Fals
             stats (bool): print internal statistics if set to True
             tests (bool): add test dependencies to the solve
         """
+        specs = [s.lookup_hash() for s in specs]
         reusable_specs = self._check_input_and_extract_concrete_specs(specs)
         reusable_specs.extend(self._reusable_specs(specs))
         setup = SpackSolverSetup(tests=tests)

lib/spack/spack/solver/counter.py

@@ -0,0 +1,159 @@
+# Copyright 2013-2023 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+import collections
+from typing import List, Set, Tuple
+
+import spack.dependency
+import spack.package_base
+
+PossibleDependencies = Set[str]
+
+
+class Counter:
+    """Computes the possible packages and the maximum number of duplicates
+    allowed for each of them.
+
+    Args:
+        specs: abstract specs to concretize
+        tests: if True, add test dependencies to the list of possible packages
+    """
+
+    def __init__(self, specs: List["spack.spec.Spec"], tests: bool) -> None:
+        self.specs = specs
+
+        self.link_run_types: Tuple[str, ...] = ("link", "run", "test")
+        self.all_types: Tuple[str, ...] = spack.dependency.all_deptypes
+        if not tests:
+            self.link_run_types = ("link", "run")
+            self.all_types = ("link", "run", "build")
+
+        self._possible_dependencies: PossibleDependencies = set()
+        self._possible_virtuals: Set[str] = set(x.name for x in specs if x.virtual)
+
+    def possible_dependencies(self) -> PossibleDependencies:
+        """Returns the list of possible dependencies"""
+        self.ensure_cache_values()
+        return self._possible_dependencies
+
+    def possible_virtuals(self) -> Set[str]:
+        """Returns the list of possible virtuals"""
+        self.ensure_cache_values()
+        return self._possible_virtuals
+
+    def ensure_cache_values(self) -> None:
+        """Ensure the cache values have been computed"""
+        if self._possible_dependencies:
+            return
+        self._compute_cache_values()
+
+    def possible_packages_facts(self, gen: "spack.solver.asp.PyclingoDriver", fn) -> None:
+        """Emit facts associated with the possible packages"""
+        raise NotImplementedError("must be implemented by derived classes")
+
+    def _compute_cache_values(self):
+        raise NotImplementedError("must be implemented by derived classes")
+
+
+class NoDuplicatesCounter(Counter):
+    def _compute_cache_values(self):
+        result = spack.package_base.possible_dependencies(
+            *self.specs, virtuals=self._possible_virtuals, deptype=self.all_types
+        )
+        self._possible_dependencies = set(result)
+
+    def possible_packages_facts(self, gen, fn):
+        gen.h2("Maximum number of nodes (packages)")
+        for package_name in sorted(self.possible_dependencies()):
+            gen.fact(fn.max_dupes(package_name, 1))
+        gen.newline()
+        gen.h2("Maximum number of nodes (virtual packages)")
+        for package_name in sorted(self.possible_virtuals()):
+            gen.fact(fn.max_dupes(package_name, 1))
+        gen.newline()
+        gen.h2("Possible package in link-run subDAG")
+        for name in sorted(self.possible_dependencies()):
+            gen.fact(fn.possible_in_link_run(name))
+        gen.newline()
+
+
+class MinimalDuplicatesCounter(NoDuplicatesCounter):
+    def __init__(self, specs, tests):
+        super().__init__(specs, tests)
+        self._link_run: PossibleDependencies = set()
+        self._direct_build: PossibleDependencies = set()
+        self._total_build: PossibleDependencies = set()
+        self._link_run_virtuals: Set[str] = set()
+
+    def _compute_cache_values(self):
+        self._link_run = set(
+            spack.package_base.possible_dependencies(
+                *self.specs, virtuals=self._possible_virtuals, deptype=self.link_run_types
+            )
+        )
+        self._link_run_virtuals.update(self._possible_virtuals)
+        for x in self._link_run:
+            current = spack.repo.PATH.get_pkg_class(x).dependencies_of_type("build")
+            self._direct_build.update(current)
+
+        self._total_build = set(
+            spack.package_base.possible_dependencies(
+                *self._direct_build, virtuals=self._possible_virtuals, deptype=self.all_types
+            )
+        )
+        self._possible_dependencies = set(self._link_run) | set(self._total_build)
+
+    def possible_packages_facts(self, gen, fn):
+        build_tools = set(spack.repo.PATH.packages_with_tags("build-tools"))
+        gen.h2("Packages with at most a single node")
+        for package_name in sorted(self.possible_dependencies() - build_tools):
+            gen.fact(fn.max_dupes(package_name, 1))
+        gen.newline()
+
+        gen.h2("Packages with at multiple possible nodes (build-tools)")
+        for package_name in sorted(self.possible_dependencies() & build_tools):
+            gen.fact(fn.max_dupes(package_name, 2))
+            gen.fact(fn.multiple_unification_sets(package_name))
+        gen.newline()
+
+        gen.h2("Maximum number of nodes (virtual packages)")
+        for package_name in sorted(self.possible_virtuals()):
+            gen.fact(fn.max_dupes(package_name, 1))
+        gen.newline()
+
+        gen.h2("Possible package in link-run subDAG")
+        for name in sorted(self._link_run):
+            gen.fact(fn.possible_in_link_run(name))
+        gen.newline()
+
+
+class FullDuplicatesCounter(MinimalDuplicatesCounter):
+    def possible_packages_facts(self, gen, fn):
+        build_tools = set(spack.repo.PATH.packages_with_tags("build-tools"))
+        counter = collections.Counter(
+            list(self._link_run) + list(self._total_build) + list(self._direct_build)
+        )
+        gen.h2("Maximum number of nodes")
+        for pkg, count in sorted(counter.items(), key=lambda x: (x[1], x[0])):
+            count = min(count, 2)
+            gen.fact(fn.max_dupes(pkg, count))
+        gen.newline()
+
+        gen.h2("Build unification sets ")
+        for name in sorted(self.possible_dependencies() & build_tools):
+            gen.fact(fn.multiple_unification_sets(name))
+        gen.newline()
+
+        gen.h2("Possible package in link-run subDAG")
+        for name in sorted(self._link_run):
+            gen.fact(fn.possible_in_link_run(name))
+        gen.newline()
+
+        counter = collections.Counter(
+            list(self._link_run_virtuals) + list(self._possible_virtuals)
+        )
+        gen.h2("Maximum number of virtual nodes")
+        for pkg, count in sorted(counter.items(), key=lambda x: (x[1], x[0])):
+            gen.fact(fn.max_dupes(pkg, count))
+        gen.newline()

lib/spack/spack/solver/cycle_detection.lp

@@ -0,0 +1,21 @@
+% Copyright 2013-2023 Lawrence Livermore National Security, LLC and other
+% Spack Project Developers. See the top-level COPYRIGHT file for details.
+%
+% SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+%=============================================================================
+% Avoid cycles in the DAG
+%
+% Some combinations of conditional dependencies can result in cycles;
+% this ensures that we solve around them. Note that these rules are quite
+% demanding on both grounding and solving, since they need to compute and
+% consider all possible paths between pair of nodes.
+%=============================================================================
+
+
+#program no_cycle.
+path(Parent, Child) :- depends_on(Parent, Child).
+path(Parent, Descendant) :- path(Parent, A), depends_on(A, Descendant).
+:- path(A, A).
+
+#defined depends_on/2.

lib/spack/spack/solver/heuristic.lp

@@ -0,0 +1,44 @@
+% Copyright 2013-2023 Lawrence Livermore National Security, LLC and other
+% Spack Project Developers. See the top-level COPYRIGHT file for details.
+%
+% SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+%=============================================================================
+% Heuristic to speed-up solves
+%=============================================================================
+
+
+%-----------------
+% Domain heuristic
+%-----------------
+#heuristic attr("hash", node(0, Package), Hash) : literal(_, "root", Package). [45, init]
+#heuristic attr("root", node(0, Package)) : literal(_, "root", Package). [45, true]
+#heuristic attr("node", node(0, Package)) : literal(_, "root", Package). [45, true]
+#heuristic attr("node", node(0, Package)) : literal(_, "node", Package). [45, true]
+
+% Root node
+#heuristic attr("version", node(0, Package), Version) : pkg_fact(Package, version_declared(Version, 0)), attr("root", node(0, Package)). [35, true]
+#heuristic version_weight(node(0, Package), 0) : pkg_fact(Package, version_declared(Version, 0)), attr("root", node(0, Package)). [35, true]
+#heuristic attr("variant_value", node(0, Package), Variant, Value) : variant_default_value(Package, Variant, Value), attr("root", node(0, Package)). [35, true]
+#heuristic attr("node_target", node(0, Package), Target) : pkg_fact(Package, target_weight(Target, 0)), attr("root", node(0, Package)). [35, true]
+#heuristic node_target_weight(node(0, Package), 0) : attr("root", node(0, Package)). [35, true]
+#heuristic node_compiler(node(0, Package), CompilerID) : default_compiler_preference(ID, 0), compiler_id(ID), attr("root", node(0, Package)). [35, true]
+
+% Providers
+#heuristic attr("node", node(0, Package)) : default_provider_preference(Virtual, Package, 0), possible_in_link_run(Package). [30, true]
+
+% node(ID, _)
+#heuristic attr("version", node(ID, Package), Version) : pkg_fact(Package, version_declared(Version, ID)), attr("node", node(ID, Package)). [25-5*ID, true]
+#heuristic version_weight(node(ID, Package), ID) : pkg_fact(Package, version_declared(Version, ID)), attr("node", node(ID, Package)). [25-5*ID, true]
+#heuristic attr("variant_value", node(ID, Package), Variant, Value) : variant_default_value(Package, Variant, Value), attr("node", node(ID, Package)). [25-5*ID, true]
+#heuristic attr("node_target", node(ID, Package), Target) : pkg_fact(Package, target_weight(Target, ID)), attr("node", node(ID, Package)). [25-5*ID, true]
+#heuristic node_target_weight(node(ID, Package), ID) : attr("node", node(ID, Package)). [25-5*ID, true]
+#heuristic node_compiler(node(ID, Package), CompilerID) : default_compiler_preference(ID, ID), compiler_id(ID), attr("node", node(ID, Package)). [25-5*ID, true]
+
+% node(ID, _), split build dependencies
+#heuristic attr("version", node(ID, Package), Version) : pkg_fact(Package, version_declared(Version, ID)), attr("node", node(ID, Package)), multiple_unification_sets(Package). [25, true]
+#heuristic version_weight(node(ID, Package), ID) : pkg_fact(Package, version_declared(Version, ID)), attr("node", node(ID, Package)), multiple_unification_sets(Package). [25, true]
+#heuristic attr("variant_value", node(ID, Package), Variant, Value) : variant_default_value(Package, Variant, Value), attr("node", node(ID, Package)), multiple_unification_sets(Package). [25, true]
+#heuristic attr("node_target", node(ID, Package), Target) : pkg_fact(Package, target_weight(Target, ID)), attr("node", node(ID, Package)), multiple_unification_sets(Package). [25, true]
+#heuristic node_target_weight(node(ID, Package), ID) : attr("node", node(ID, Package)), multiple_unification_sets(Package). [25, true]
+#heuristic node_compiler(node(ID, Package), CompilerID) : default_compiler_preference(ID, ID), compiler_id(ID), attr("node", node(ID, Package)), multiple_unification_sets(Package). [25, true]

lib/spack/spack/solver/os_compatibility.lp

@@ -3,9 +3,11 @@
 %
 % SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
+%=============================================================================
 % OS compatibility rules for reusing solves.
 % os_compatible(RecentOS, OlderOS)
 % OlderOS binaries can be used on RecentOS
+%=============================================================================
 
 % macOS
 os_compatible("monterey", "bigsur").

lib/spack/spack/solver/when_possible.lp

@@ -0,0 +1,27 @@
+% Copyright 2013-2023 Lawrence Livermore National Security, LLC and other
+% Spack Project Developers. See the top-level COPYRIGHT file for details.
+%
+% SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+%=============================================================================
+% Minimize the number of literals that are not solved
+%
+% This minimization is used for the "when_possible" concretization mode,
+% otherwise we assume that all literals must be solved.
+%=============================================================================
+
+% Give clingo the choice to solve an input spec or not
+{ solve_literal(ID) } :- literal(ID).
+literal_not_solved(ID) :- not solve_literal(ID), literal(ID).
+
+% Make a problem with "zero literals solved" unsat. This is to trigger
+% looking for solutions to the ASP problem with "errors", which results
+% in better reporting for users. See #30669 for details.
+1 { solve_literal(ID) : literal(ID) }.
+
+opt_criterion(300, "number of input specs not concretized").
+#minimize{ 0@300: #true }.
+#minimize { 1@300,ID : literal_not_solved(ID) }.
+
+#heuristic literal_solved(ID) : literal(ID). [1, sign]
+#heuristic literal_solved(ID) : literal(ID). [50, init]

lib/spack/spack/spec.py

@@ -985,16 +985,14 @@ def __iter__(self):
     def __len__(self):
         return len(self.edges)
 
-    def add(self, edge):
-        """Adds a new edge to this object.
-
-        Args:
-            edge (DependencySpec): edge to be added
-        """
+    def add(self, edge: DependencySpec):
         key = edge.spec.name if self.store_by_child else edge.parent.name
-        current_list = self.edges.setdefault(key, [])
-        current_list.append(edge)
-        current_list.sort(key=_sort_by_dep_types)
+        if key in self.edges:
+            lst = self.edges[key]
+            lst.append(edge)
+            lst.sort(key=_sort_by_dep_types)
+        else:
+            self.edges[key] = [edge]
 
     def __str__(self):
         return "{deps: %s}" % ", ".join(str(d) for d in sorted(self.values()))
@@ -1927,19 +1925,15 @@ def _lookup_hash(self):
         store, or finally, binary caches."""
         import spack.environment
 
-        matches = []
         active_env = spack.environment.active_environment()
 
-        if active_env:
-            env_matches = active_env.get_by_hash(self.abstract_hash) or []
-            matches = [m for m in env_matches if m._satisfies(self)]
-        if not matches:
-            db_matches = spack.store.STORE.db.get_by_hash(self.abstract_hash) or []
-            matches = [m for m in db_matches if m._satisfies(self)]
-        if not matches:
-            query = spack.binary_distribution.BinaryCacheQuery(True)
-            remote_matches = query("/" + self.abstract_hash) or []
-            matches = [m for m in remote_matches if m._satisfies(self)]
+        # First env, then store, then binary cache
+        matches = (
+            (active_env.all_matching_specs(self) if active_env else [])
+            or spack.store.STORE.db.query(self, installed=any)
+            or spack.binary_distribution.BinaryCacheQuery(True)(self)
+        )
+
         if not matches:
             raise InvalidHashError(self, self.abstract_hash)
 
@@ -1960,19 +1954,17 @@ def lookup_hash(self):
         spec = self.copy(deps=False)
         # root spec is replaced
         if spec.abstract_hash:
-            new = self._lookup_hash()
-            spec._dup(new)
+            spec._dup(self._lookup_hash())
             return spec
 
         # Get dependencies that need to be replaced
         for node in self.traverse(root=False):
             if node.abstract_hash:
-                new = node._lookup_hash()
-                spec._add_dependency(new, deptypes=(), virtuals=())
+                spec._add_dependency(node._lookup_hash(), deptypes=(), virtuals=())
 
         # reattach nodes that were not otherwise satisfied by new dependencies
         for node in self.traverse(root=False):
-            if not any(n._satisfies(node) for n in spec.traverse()):
+            if not any(n.satisfies(node) for n in spec.traverse()):
                 spec._add_dependency(node.copy(), deptypes=(), virtuals=())
 
         return spec
@@ -1985,9 +1977,7 @@ def replace_hash(self):
         if not any(node for node in self.traverse(order="post") if node.abstract_hash):
             return
 
-        spec_by_hash = self.lookup_hash()
-
-        self._dup(spec_by_hash)
+        self._dup(self.lookup_hash())
 
     def to_node_dict(self, hash=ht.dag_hash):
         """Create a dictionary representing the state of this Spec.
@@ -2983,9 +2973,12 @@ def _new_concretize(self, tests=False):
             providers = [spec.name for spec in answer.values() if spec.package.provides(name)]
             name = providers[0]
 
-        assert name in answer
+        node = spack.solver.asp.SpecBuilder.make_node(pkg=name)
+        assert (
+            node in answer
+        ), f"cannot find {name} in the list of specs {','.join([n.pkg for n in answer.keys()])}"
 
-        concretized = answer[name]
+        concretized = answer[node]
         self._dup(concretized)
 
     def concretize(self, tests=False):
@@ -3519,7 +3512,8 @@ def update_variant_validate(self, variant_name, values):
         for value in values:
             if self.variants.get(variant_name):
                 msg = (
-                    "Cannot append a value to a single-valued " "variant with an already set value"
+                    f"cannot append the new value '{value}' to the single-valued "
+                    f"variant '{self.variants[variant_name]}'"
                 )
                 assert pkg_variant.multi, msg
                 self.variants[variant_name].append(value)
@@ -3719,15 +3713,19 @@ def intersects(self, other: "Spec", deps: bool = True) -> bool:
         """
         other = self._autospec(other)
 
-        lhs = self.lookup_hash() or self
-        rhs = other.lookup_hash() or other
-
-        return lhs._intersects(rhs, deps)
-
-    def _intersects(self, other: "Spec", deps: bool = True) -> bool:
         if other.concrete and self.concrete:
             return self.dag_hash() == other.dag_hash()
 
+        self_hash = self.dag_hash() if self.concrete else self.abstract_hash
+        other_hash = other.dag_hash() if other.concrete else other.abstract_hash
+
+        if (
+            self_hash
+            and other_hash
+            and not (self_hash.startswith(other_hash) or other_hash.startswith(self_hash))
+        ):
+            return False
+
         # If the names are different, we need to consider virtuals
         if self.name != other.name and self.name and other.name:
             if self.virtual and other.virtual:
@@ -3787,19 +3785,8 @@ def _intersects(self, other: "Spec", deps: bool = True) -> bool:
         # If we need to descend into dependencies, do it, otherwise we're done.
         if deps:
             return self._intersects_dependencies(other)
-        else:
-            return True
 
-    def satisfies(self, other, deps=True):
-        """
-        This checks constraints on common dependencies against each other.
-        """
-        other = self._autospec(other)
-
-        lhs = self.lookup_hash() or self
-        rhs = other.lookup_hash() or other
-
-        return lhs._satisfies(rhs, deps=deps)
+        return True
 
     def _intersects_dependencies(self, other):
         if not other._dependencies or not self._dependencies:
@@ -3836,7 +3823,7 @@ def _intersects_dependencies(self, other):
 
         return True
 
-    def _satisfies(self, other: "Spec", deps: bool = True) -> bool:
+    def satisfies(self, other: "Spec", deps: bool = True) -> bool:
         """Return True if all concrete specs matching self also match other, otherwise False.
 
         Args:
@@ -3851,6 +3838,13 @@ def _satisfies(self, other: "Spec", deps: bool = True) -> bool:
             # objects.
             return self.concrete and self.dag_hash() == other.dag_hash()
 
+        # If the right-hand side has an abstract hash, make sure it's a prefix of the
+        # left-hand side's (abstract) hash.
+        if other.abstract_hash:
+            compare_hash = self.dag_hash() if self.concrete else self.abstract_hash
+            if not compare_hash or not compare_hash.startswith(other.abstract_hash):
+                return False
+
         # If the names are different, we need to consider virtuals
         if self.name != other.name and self.name and other.name:
             # A concrete provider can satisfy a virtual dependency.
@@ -4227,9 +4221,7 @@ def eq_node(self, other):
     def _cmp_iter(self):
         """Lazily yield components of self for comparison."""
 
-        cmp_spec = self.lookup_hash() or self
-
-        for item in cmp_spec._cmp_node():
+        for item in self._cmp_node():
             yield item
 
         # This needs to be in _cmp_iter so that no specs with different process hashes
@@ -4240,10 +4232,10 @@ def _cmp_iter(self):
         # TODO: they exist for speed.  We should benchmark whether it's really worth
         # TODO: having two types of hashing now that we use `json` instead of `yaml` for
         # TODO: spec hashing.
-        yield cmp_spec.process_hash() if cmp_spec.concrete else None
+        yield self.process_hash() if self.concrete else None
 
         def deps():
-            for dep in sorted(itertools.chain.from_iterable(cmp_spec._dependencies.values())):
+            for dep in sorted(itertools.chain.from_iterable(self._dependencies.values())):
                 yield dep.spec.name
                 yield tuple(sorted(dep.deptypes))
                 yield hash(dep.spec)
@@ -4315,6 +4307,19 @@ def format(self, format_string=default_format, **kwargs):
         ``\{`` and ``\}`` for literal braces, and ``\\`` for the
         literal ``\`` character.
 
+        The ``?`` sigil may be used to conditionally add a
+        value. Conditional format values are used if constructing the
+        value would not throw any error, and are ignored if it would
+        throw an error. For example, ``{?^mpi.name}`` will print
+        ``Spec["mpi"].name`` if such a node exists, and otherwise
+        prints nothing.
+
+        The ``?`` sigil may also be combined with a conditional
+        separator. This separator is prepended if anything is printed
+        for the conditional attribute. The syntax for this is
+        ``?sep?attribute``,
+        e.g. ``{name}-{version}{?/?^mpi.name}{?-?^mpi.version}``.
+
         Args:
             format_string (str): string containing the format to be expanded
 
@@ -4338,6 +4343,15 @@ def write(s, c=None):
         def write_attribute(spec, attribute, color):
             attribute = attribute.lower()
 
+            conditional = False
+            conditional_sep = ""
+            matches_conditional_sep = re.match(r"^\?(.*)\?", attribute)
+            if matches_conditional_sep:
+                conditional = True
+                conditional_sep = matches_conditional_sep.group(1)
+            if attribute.startswith("?"):
+                conditional = True
+
             sig = ""
             if attribute.startswith(("@", "%", "/")):
                 # color sigils that are inside braces
@@ -4369,6 +4383,9 @@ def write_attribute(spec, attribute, color):
             elif sig == " arch=" and attribute not in ("architecture", "arch"):
                 raise SpecFormatSigilError(sig, "the architecture", attribute)
 
+            # Now that we're done testing sig, combine it with conditional sep
+            sig = conditional_sep + sig
+
             # find the morph function for our attribute
             morph = transform.get(attribute, lambda s, x: x)
 
@@ -4398,7 +4415,12 @@ def write_attribute(spec, attribute, color):
                 else:
                     if isinstance(current, vt.VariantMap):
                         # subscript instead of getattr for variant names
-                        current = current[part]
+                        try:
+                            current = current[part]
+                        except KeyError:
+                            if conditional:
+                                return
+                            raise
                     else:
                         # aliases
                         if part == "arch":
@@ -4414,6 +4436,8 @@ def write_attribute(spec, attribute, color):
                         try:
                             current = getattr(current, part)
                         except AttributeError:
+                            if conditional:
+                                return
                             parent = ".".join(parts[:idx])
                             m = "Attempted to format attribute %s." % attribute
                             m += "Spec %s has no attribute %s" % (parent, part)

lib/spack/spack/spec_list.py

@@ -197,7 +197,9 @@ def _expand_matrix_constraints(matrix_config):
     for combo in itertools.product(*expanded_rows):
         # Construct a combined spec to test against excludes
         flat_combo = [constraint for constraint_list in combo for constraint in constraint_list]
-        flat_combo = [Spec(x) for x in flat_combo]
+
+        # Resolve abstract hashes so we can exclude by their concrete properties
+        flat_combo = [Spec(x).lookup_hash() for x in flat_combo]
 
         test_spec = flat_combo[0].copy()
         for constraint in flat_combo[1:]:

lib/spack/spack/stage.py

@@ -484,7 +484,7 @@ def fetch(self, mirror_only=False, err_msg=None):
 
             if self.default_fetcher.cachable:
                 for rel_path in reversed(list(self.mirror_paths)):
-                    cache_fetcher = spack.caches.fetch_cache.fetcher(
+                    cache_fetcher = spack.caches.FETCH_CACHE.fetcher(
                         rel_path, digest, expand=expand, extension=extension
                     )
                     fetchers.insert(0, cache_fetcher)
@@ -577,7 +577,7 @@ def check(self):
             self.fetcher.check()
 
     def cache_local(self):
-        spack.caches.fetch_cache.store(self.fetcher, self.mirror_paths.storage_path)
+        spack.caches.FETCH_CACHE.store(self.fetcher, self.mirror_paths.storage_path)
 
     def cache_mirror(self, mirror, stats):
         """Perform a fetch if the resource is not already cached

lib/spack/spack/store.py

@@ -212,7 +212,7 @@ def create(configuration: ConfigurationType) -> Store:
     Args:
         configuration: configuration to create a store.
     """
-    configuration = configuration or spack.config.config
+    configuration = configuration or spack.config.CONFIG
     config_dict = configuration.get("config")
     root, unpadded_root, projections = parse_install_tree(config_dict)
     hash_length = configuration.get("config:install_hash_length")
@@ -234,7 +234,7 @@ def create(configuration: ConfigurationType) -> Store:
 
 
 def _create_global() -> Store:
-    result = create(configuration=spack.config.config)
+    result = create(configuration=spack.config.CONFIG)
     return result
 
 
@@ -372,10 +372,10 @@ def use_store(
 
     # Swap the store with the one just constructed and return it
     ensure_singleton_created()
-    spack.config.config.push_scope(
+    spack.config.CONFIG.push_scope(
         spack.config.InternalConfigScope(name=scope_name, data={"config": {"install_tree": data}})
     )
-    temporary_store = create(configuration=spack.config.config)
+    temporary_store = create(configuration=spack.config.CONFIG)
     original_store, STORE = STORE, temporary_store
 
     try:
@@ -383,7 +383,7 @@ def use_store(
     finally:
         # Restore the original store
         STORE = original_store
-        spack.config.config.remove_scope(scope_name=scope_name)
+        spack.config.CONFIG.remove_scope(scope_name=scope_name)
 
 
 class MatchError(spack.error.SpackError):

lib/spack/spack/subprocess_context.py

@@ -94,14 +94,14 @@ class TestState:
 
     def __init__(self):
         if _SERIALIZE:
-            self.config = spack.config.config
+            self.config = spack.config.CONFIG
             self.platform = spack.platforms.host
             self.test_patches = store_patches()
             self.store = spack.store.STORE
 
     def restore(self):
         if _SERIALIZE:
-            spack.config.config = self.config
+            spack.config.CONFIG = self.config
             spack.repo.PATH = spack.repo.create(self.config)
             spack.platforms.host = self.platform
             spack.store.STORE = self.store

lib/spack/spack/test/architecture.py

@@ -199,15 +199,11 @@ def test_satisfy_strict_constraint_when_not_concrete(architecture_tuple, constra
     ],
 )
 @pytest.mark.usefixtures("mock_packages", "config")
+@pytest.mark.only_clingo("Fixing the parser broke this test for the original concretizer.")
 def test_concretize_target_ranges(root_target_range, dep_target_range, result, monkeypatch):
     # Monkeypatch so that all concretization is done as if the machine is core2
     monkeypatch.setattr(spack.platforms.test.Test, "default", "core2")
 
-    # use foobar=bar to make the problem simpler for the old concretizer
-    # the new concretizer should not need that help
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Fixing the parser broke this test for the original concretizer.")
-
     spec_str = "a %%gcc@10 foobar=bar target=%s ^b target=%s" % (
         root_target_range,
         dep_target_range,

lib/spack/spack/test/bindist.py

@@ -37,7 +37,7 @@
 from spack.paths import test_path
 from spack.spec import Spec
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 mirror_cmd = spack.main.SpackCommand("mirror")
 install_cmd = spack.main.SpackCommand("install")
@@ -51,7 +51,7 @@
 def cache_directory(tmpdir):
     fetch_cache_dir = tmpdir.ensure("fetch_cache", dir=True)
     fsc = spack.fetch_strategy.FsCache(str(fetch_cache_dir))
-    spack.config.caches, old_cache_path = fsc, spack.caches.fetch_cache
+    spack.config.caches, old_cache_path = fsc, spack.caches.FETCH_CACHE
 
     yield spack.config.caches
 
@@ -115,8 +115,8 @@ def default_config(tmpdir, config_directory, monkeypatch, install_mockery_mutabl
         ]
     )
 
-    spack.config.config, old_config = cfg, spack.config.config
-    spack.config.config.set("repos", [spack.paths.mock_packages_path])
+    spack.config.CONFIG, old_config = cfg, spack.config.CONFIG
+    spack.config.CONFIG.set("repos", [spack.paths.mock_packages_path])
     njobs = spack.config.get("config:build_jobs")
     if not njobs:
         spack.config.set("config:build_jobs", 4, scope="user")
@@ -138,9 +138,9 @@ def default_config(tmpdir, config_directory, monkeypatch, install_mockery_mutabl
     if not timeout:
         spack.config.set("config:connect_timeout", 10, scope="user")
 
-    yield spack.config.config
+    yield spack.config.CONFIG
 
-    spack.config.config = old_config
+    spack.config.CONFIG = old_config
     mutable_dir.remove()
 
 

lib/spack/spack/test/bootstrap.py

@@ -26,11 +26,11 @@ def test_store_is_restored_correctly_after_bootstrap(mutable_config, tmpdir):
     user_path = str(tmpdir.join("store"))
     with spack.store.use_store(user_path):
         assert spack.store.STORE.root == user_path
-        assert spack.config.config.get("config:install_tree:root") == user_path
+        assert spack.config.CONFIG.get("config:install_tree:root") == user_path
         with spack.bootstrap.ensure_bootstrap_configuration():
             assert spack.store.STORE.root == spack.bootstrap.config.store_path()
         assert spack.store.STORE.root == user_path
-        assert spack.config.config.get("config:install_tree:root") == user_path
+        assert spack.config.CONFIG.get("config:install_tree:root") == user_path
 
 
 @pytest.mark.regression("38963")
@@ -40,11 +40,11 @@ def test_store_padding_length_is_zero_during_bootstrapping(mutable_config, tmpdi
     """
     user_path = str(tmpdir.join("store"))
     with spack.store.use_store(user_path, extra_data={"padded_length": 512}):
-        assert spack.config.config.get("config:install_tree:padded_length") == 512
+        assert spack.config.CONFIG.get("config:install_tree:padded_length") == 512
         with spack.bootstrap.ensure_bootstrap_configuration():
             assert spack.store.STORE.root == spack.bootstrap.config.store_path()
-            assert spack.config.config.get("config:install_tree:padded_length") == 0
-        assert spack.config.config.get("config:install_tree:padded_length") == 512
+            assert spack.config.CONFIG.get("config:install_tree:padded_length") == 0
+        assert spack.config.CONFIG.get("config:install_tree:padded_length") == 512
 
 
 @pytest.mark.regression("38963")
@@ -54,15 +54,15 @@ def test_install_tree_customization_is_respected(mutable_config, tmp_path):
     """
     spack.store.reinitialize()
     store_dir = tmp_path / "store"
-    spack.config.config.set("config:install_tree:root", str(store_dir))
+    spack.config.CONFIG.set("config:install_tree:root", str(store_dir))
     with spack.bootstrap.ensure_bootstrap_configuration():
         assert spack.store.STORE.root == spack.bootstrap.config.store_path()
         assert (
-            spack.config.config.get("config:install_tree:root")
+            spack.config.CONFIG.get("config:install_tree:root")
             == spack.bootstrap.config.store_path()
         )
-        assert spack.config.config.get("config:install_tree:padded_length") == 0
-    assert spack.config.config.get("config:install_tree:root") == str(store_dir)
+        assert spack.config.CONFIG.get("config:install_tree:padded_length") == 0
+    assert spack.config.CONFIG.get("config:install_tree:root") == str(store_dir)
     assert spack.store.STORE.root == str(store_dir)
 
 
@@ -185,12 +185,12 @@ def test_bootstrap_custom_store_in_environment(mutable_config, tmpdir):
 
 def test_nested_use_of_context_manager(mutable_config):
     """Test nested use of the context manager"""
-    user_config = spack.config.config
+    user_config = spack.config.CONFIG
     with spack.bootstrap.ensure_bootstrap_configuration():
-        assert spack.config.config != user_config
+        assert spack.config.CONFIG != user_config
         with spack.bootstrap.ensure_bootstrap_configuration():
-            assert spack.config.config != user_config
-    assert spack.config.config == user_config
+            assert spack.config.CONFIG != user_config
+    assert spack.config.CONFIG == user_config
 
 
 @pytest.mark.parametrize("expected_missing", [False, True])

lib/spack/spack/test/build_distribution.py

@@ -5,7 +5,6 @@
 
 import os
 import os.path
-import sys
 
 import pytest
 
@@ -16,7 +15,7 @@
 
 install = spack.main.SpackCommand("install")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 def test_build_tarball_overwrite(install_mockery, mock_fetch, monkeypatch, tmpdir):

lib/spack/spack/test/build_environment.py

@@ -6,7 +6,6 @@
 import os
 import platform
 import posixpath
-import sys
 
 import pytest
 
@@ -119,7 +118,7 @@ def __call__(self, *args, **kwargs):
     return mock_module_cmd
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Static to Shared not supported on Win (yet)")
+@pytest.mark.not_on_windows("Static to Shared not supported on Win (yet)")
 def test_static_to_shared_library(build_environment):
     os.environ["SPACK_TEST_COMMAND"] = "dump-args"
 

lib/spack/spack/test/build_systems.py

@@ -5,7 +5,6 @@
 
 import glob
 import os
-import sys
 
 import py.path
 import pytest
@@ -43,7 +42,7 @@ def _func(dir_str):
     return _func
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="make not available on Windows")
+@pytest.mark.not_on_windows("make not available on Windows")
 @pytest.mark.usefixtures("config", "mock_packages", "working_env")
 class TestTargets:
     @pytest.mark.parametrize(
@@ -92,7 +91,7 @@ def test_negative_ninja_check(self, input_dir, test_dir, concretize_and_setup):
             s.package._if_ninja_target_execute("check")
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="autotools not available on windows")
+@pytest.mark.not_on_windows("autotools not available on windows")
 @pytest.mark.usefixtures("config", "mock_packages")
 class TestAutotoolsPackage:
     def test_with_or_without(self, default_mock_concretization):

lib/spack/spack/test/builder.py

@@ -3,7 +3,6 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 import os.path
-import sys
 
 import pytest
 
@@ -106,10 +105,7 @@ def test_old_style_compatibility_with_super(spec_str, method_name, expected):
     assert value == expected
 
 
-@pytest.mark.skipif(
-    sys.platform == "win32",
-    reason="log_ouput cannot currently be used outside of subprocess on Windows",
-)
+@pytest.mark.not_on_windows("log_ouput cannot currently be used outside of subprocess on Windows")
 @pytest.mark.regression("33928")
 @pytest.mark.usefixtures("builder_test_repository", "config", "working_env")
 @pytest.mark.disable_clean_stage_check
@@ -153,7 +149,7 @@ def test_monkey_patching_test_log_file():
 
 # Windows context manager's __exit__ fails with ValueError ("I/O operation
 # on closed file").
-@pytest.mark.skipif(sys.platform == "win32", reason="Does not run on windows")
+@pytest.mark.not_on_windows("Does not run on windows")
 def test_install_time_test_callback(tmpdir, config, mock_packages, mock_stage):
     """Confirm able to run stand-alone test as a post-install callback."""
     s = spack.spec.Spec("py-test-callback").concretized()

lib/spack/spack/test/cc.py

@@ -8,7 +8,6 @@
 arguments correctly.
 """
 import os
-import sys
 
 import pytest
 
@@ -145,7 +144,7 @@
     + test_args_without_paths
 )
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 @pytest.fixture(scope="function")

lib/spack/spack/test/ci.py

@@ -5,7 +5,6 @@
 import itertools
 import os
 import subprocess
-import sys
 
 import pytest
 
@@ -35,7 +34,7 @@ def test_urlencode_string():
     assert ci._url_encode_string("Spack Test Project") == "Spack+Test+Project"
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Not supported on Windows (yet)")
+@pytest.mark.not_on_windows("Not supported on Windows (yet)")
 def test_import_signing_key(mock_gnupghome):
     signing_key_dir = spack_paths.mock_gpg_keys_path
     signing_key_path = os.path.join(signing_key_dir, "package-signing-key")
@@ -427,18 +426,14 @@ def test_affected_specs_on_first_concretization(mutable_mock_env_path, mock_pack
     assert len(mpileaks_specs) == 2, e.all_specs()
 
 
-@pytest.mark.skipif(
-    sys.platform == "win32", reason="Reliance on bash script not supported on Windows"
-)
+@pytest.mark.not_on_windows("Reliance on bash script not supported on Windows")
 def test_ci_process_command(repro_dir):
     result = ci.process_command("help", commands=[], repro_dir=str(repro_dir))
     help_sh = repro_dir / "help.sh"
     assert help_sh.exists() and not result
 
 
-@pytest.mark.skipif(
-    sys.platform == "win32", reason="Reliance on bash script not supported on Windows"
-)
+@pytest.mark.not_on_windows("Reliance on bash script not supported on Windows")
 def test_ci_process_command_fail(repro_dir, monkeypatch):
     msg = "subprocess wait exception"
 
@@ -489,9 +484,7 @@ def test_ci_run_standalone_tests_missing_requirements(
     assert "Reproduction directory is required" in err
 
 
-@pytest.mark.skipif(
-    sys.platform == "win32", reason="Reliance on bash script not supported on Windows"
-)
+@pytest.mark.not_on_windows("Reliance on bash script not supported on Windows")
 def test_ci_run_standalone_tests_not_installed_junit(
     tmp_path, repro_dir, working_env, default_mock_concretization, mock_test_stage, capfd
 ):
@@ -509,9 +502,7 @@ def test_ci_run_standalone_tests_not_installed_junit(
     assert os.path.getsize(log_file) > 0
 
 
-@pytest.mark.skipif(
-    sys.platform == "win32", reason="Reliance on bash script not supported on Windows"
-)
+@pytest.mark.not_on_windows("Reliance on bash script not supported on Windows")
 def test_ci_run_standalone_tests_not_installed_cdash(
     tmp_path, repro_dir, working_env, default_mock_concretization, mock_test_stage, capfd
 ):

lib/spack/spack/test/cmd/blame.py

@@ -3,8 +3,6 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
-import sys
-
 import pytest
 
 from llnl.util.filesystem import working_dir
@@ -35,7 +33,7 @@ def test_blame_by_percent(mock_packages):
     assert "EMAIL" in out
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Not supported on Windows (yet)")
+@pytest.mark.not_on_windows("Not supported on Windows (yet)")
 def test_blame_file(mock_packages):
     """Sanity check the blame command to make sure it works."""
     with working_dir(spack.paths.prefix):
@@ -68,7 +66,7 @@ def test_blame_json(mock_packages):
         assert key in loaded["authors"][0]
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="git hangs")
+@pytest.mark.not_on_windows("git hangs")
 def test_blame_by_git(mock_packages, capfd):
     """Sanity check the blame command to make sure it works."""
     with capfd.disabled():

lib/spack/spack/test/cmd/bootstrap.py

@@ -50,7 +50,7 @@ def test_reset_in_file_scopes(mutable_config, scopes):
     bootstrap_yaml_files = []
     for s in scopes:
         _bootstrap("disable", "--scope={0}".format(s))
-        scope_path = spack.config.config.scopes[s].path
+        scope_path = spack.config.CONFIG.scopes[s].path
         bootstrap_yaml = os.path.join(scope_path, "bootstrap.yaml")
         assert os.path.exists(bootstrap_yaml)
         bootstrap_yaml_files.append(bootstrap_yaml)
@@ -80,7 +80,7 @@ def test_reset_in_environment(mutable_mock_env_path, mutable_config):
 def test_reset_in_file_scopes_overwrites_backup_files(mutable_config):
     # Create a bootstrap.yaml with some config
     _bootstrap("disable", "--scope=site")
-    scope_path = spack.config.config.scopes["site"].path
+    scope_path = spack.config.CONFIG.scopes["site"].path
     bootstrap_yaml = os.path.join(scope_path, "bootstrap.yaml")
     assert os.path.exists(bootstrap_yaml)
 
@@ -174,7 +174,7 @@ def test_remove_and_add_a_source(mutable_config):
 
 
 @pytest.mark.maybeslow
-@pytest.mark.skipif(sys.platform == "win32", reason="Not supported on Windows (yet)")
+@pytest.mark.not_on_windows("Not supported on Windows (yet)")
 def test_bootstrap_mirror_metadata(mutable_config, linux_os, monkeypatch, tmpdir):
     """Test that `spack bootstrap mirror` creates a folder that can be ingested by
     `spack bootstrap add`. Here we don't download data, since that would be an

lib/spack/spack/test/cmd/build_env.py

@@ -54,7 +54,7 @@ def test_pickle(tmpdir):
     with tmpdir.as_cwd():
         build_env("--pickle", _out_file, "zlib")
         environment = pickle.load(open(_out_file, "rb"))
-        assert type(environment) == dict
+        assert isinstance(environment, dict)
         assert "PATH" in environment
 
 

lib/spack/spack/test/cmd/buildcache.py

@@ -6,7 +6,6 @@
 import errno
 import os
 import shutil
-import sys
 
 import pytest
 
@@ -26,7 +25,7 @@
 mirror = spack.main.SpackCommand("mirror")
 uninstall = spack.main.SpackCommand("uninstall")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 @pytest.fixture()

lib/spack/spack/test/cmd/checksum.py

@@ -4,7 +4,6 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
 import argparse
-import sys
 
 import pytest
 
@@ -36,7 +35,7 @@ def test_checksum_args(arguments, expected):
     assert check == expected
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Not supported on Windows (yet)")
+@pytest.mark.not_on_windows("Not supported on Windows (yet)")
 @pytest.mark.parametrize(
     "arguments,expected",
     [
@@ -57,7 +56,7 @@ def test_checksum(arguments, expected, mock_packages, mock_clone_repo, mock_stag
         assert "version(" in output
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Not supported on Windows (yet)")
+@pytest.mark.not_on_windows("Not supported on Windows (yet)")
 def test_checksum_interactive(mock_packages, mock_fetch, mock_stage, monkeypatch):
     # TODO: mock_fetch doesn't actually work with stage, working around with ignoring
     # fail_on_error for now

lib/spack/spack/test/cmd/ci.py

@@ -7,7 +7,6 @@
 import json
 import os
 import shutil
-import sys
 
 import jsonschema
 import pytest
@@ -41,10 +40,7 @@
 uninstall_cmd = spack.main.SpackCommand("uninstall")
 buildcache_cmd = spack.main.SpackCommand("buildcache")
 
-pytestmark = [
-    pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows"),
-    pytest.mark.maybeslow,
-]
+pytestmark = [pytest.mark.not_on_windows("does not run on windows"), pytest.mark.maybeslow]
 
 
 @pytest.fixture()

lib/spack/spack/test/cmd/clean.py

@@ -33,8 +33,8 @@ def __call__(self, *args, **kwargs):
 
     monkeypatch.setattr(spack.package_base.PackageBase, "do_clean", Counter("package"))
     monkeypatch.setattr(spack.stage, "purge", Counter("stages"))
-    monkeypatch.setattr(spack.caches.fetch_cache, "destroy", Counter("downloads"), raising=False)
-    monkeypatch.setattr(spack.caches.misc_cache, "destroy", Counter("caches"))
+    monkeypatch.setattr(spack.caches.FETCH_CACHE, "destroy", Counter("downloads"), raising=False)
+    monkeypatch.setattr(spack.caches.MISC_CACHE, "destroy", Counter("caches"))
     monkeypatch.setattr(spack.store.STORE.failure_tracker, "clear_all", Counter("failures"))
     monkeypatch.setattr(spack.cmd.clean, "remove_python_cache", Counter("python_cache"))
 

lib/spack/spack/test/cmd/commands.py

@@ -7,7 +7,6 @@
 import os
 import shutil
 import subprocess
-import sys
 
 import pytest
 
@@ -254,9 +253,7 @@ def test_update_completion_arg(shell, tmpdir, monkeypatch):
 
 
 # Note: this test is never expected to be supported on Windows
-@pytest.mark.skipif(
-    sys.platform == "win32", reason="shell completion script generator fails on windows"
-)
+@pytest.mark.not_on_windows("Shell completion script generator fails on windows")
 @pytest.mark.parametrize("shell", ["bash", "fish"])
 def test_updated_completion_scripts(shell, tmpdir):
     """Make sure our shell tab completion scripts remain up-to-date."""

lib/spack/spack/test/cmd/compiler.py

@@ -64,7 +64,7 @@ def compilers_dir(mock_executable):
     return clang_path.parent
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Cannot execute bash script on Windows")
+@pytest.mark.not_on_windows("Cannot execute bash script on Windows")
 @pytest.mark.regression("11678,13138")
 def test_compiler_find_without_paths(no_compilers_yaml, working_env, mock_executable):
     """Tests that 'spack compiler find' looks into PATH by default, if no specific path
@@ -127,7 +127,7 @@ def test_removing_compilers_from_multiple_scopes(mutable_config, mock_packages):
     assert spack.spec.CompilerSpec("gcc@=4.5.0") not in spack.compilers.all_compiler_specs()
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Cannot execute bash script on Windows")
+@pytest.mark.not_on_windows("Cannot execute bash script on Windows")
 def test_compiler_add(mutable_config, mock_packages, mock_executable):
     """Tests that we can add a compiler to configuration."""
     expected_version = "4.5.3"
@@ -157,7 +157,7 @@ def test_compiler_add(mutable_config, mock_packages, mock_executable):
     assert new_compiler.version == spack.version.Version(expected_version)
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Cannot execute bash script on Windows")
+@pytest.mark.not_on_windows("Cannot execute bash script on Windows")
 @pytest.mark.regression("17590")
 def test_compiler_find_mixed_suffixes(no_compilers_yaml, working_env, compilers_dir):
     """Ensure that we'll mix compilers with different suffixes when necessary."""
@@ -189,7 +189,7 @@ def test_compiler_find_mixed_suffixes(no_compilers_yaml, working_env, compilers_
     }
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Cannot execute bash script on Windows")
+@pytest.mark.not_on_windows("Cannot execute bash script on Windows")
 @pytest.mark.regression("17590")
 def test_compiler_find_prefer_no_suffix(no_compilers_yaml, working_env, compilers_dir):
     """Ensure that we'll pick 'clang' over 'clang-gpu' when there is a choice."""
@@ -210,7 +210,7 @@ def test_compiler_find_prefer_no_suffix(no_compilers_yaml, working_env, compiler
     assert clang["paths"]["cxx"] == str(compilers_dir / "clang++")
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Cannot execute bash script on Windows")
+@pytest.mark.not_on_windows("Cannot execute bash script on Windows")
 def test_compiler_find_path_order(no_compilers_yaml, working_env, compilers_dir):
     """Ensure that we look for compilers in the same order as PATH, when there are duplicates"""
     new_dir = compilers_dir / "first_in_path"

lib/spack/spack/test/cmd/config.py

@@ -24,7 +24,7 @@
 
 def _create_config(scope=None, data={}, section="packages"):
     scope = scope or spack.config.default_modify_scope()
-    cfg_file = spack.config.config.get_config_filename(scope, section)
+    cfg_file = spack.config.CONFIG.get_config_filename(scope, section)
     with open(cfg_file, "w") as f:
         syaml.dump(data, stream=f)
     return cfg_file
@@ -80,8 +80,8 @@ def test_config_edit(mutable_config, working_env):
     """Ensure `spack config edit` edits the right paths."""
 
     dms = spack.config.default_modify_scope("compilers")
-    dms_path = spack.config.config.scopes[dms].path
-    user_path = spack.config.config.scopes["user"].path
+    dms_path = spack.config.CONFIG.scopes[dms].path
+    user_path = spack.config.CONFIG.scopes["user"].path
 
     comp_path = os.path.join(dms_path, "compilers.yaml")
     repos_path = os.path.join(user_path, "repos.yaml")
@@ -544,7 +544,7 @@ def test_config_update_not_needed(mutable_config):
 def test_config_update_can_handle_comments(mutable_config):
     # Create an outdated config file with comments
     scope = spack.config.default_modify_scope()
-    cfg_file = spack.config.config.get_config_filename(scope, "config")
+    cfg_file = spack.config.CONFIG.get_config_filename(scope, "config")
     with open(cfg_file, mode="w") as f:
         f.write(
             """
@@ -574,7 +574,7 @@ def test_config_update_can_handle_comments(mutable_config):
 @pytest.mark.regression("18050")
 def test_config_update_works_for_empty_paths(mutable_config):
     scope = spack.config.default_modify_scope()
-    cfg_file = spack.config.config.get_config_filename(scope, "config")
+    cfg_file = spack.config.CONFIG.get_config_filename(scope, "config")
     with open(cfg_file, mode="w") as f:
         f.write(
             """
@@ -627,7 +627,7 @@ def test_config_prefer_upstream(
 
     output = config("prefer-upstream")
     scope = spack.config.default_modify_scope("packages")
-    cfg_file = spack.config.config.get_config_filename(scope, "packages")
+    cfg_file = spack.config.CONFIG.get_config_filename(scope, "packages")
     packages = syaml.load(open(cfg_file))["packages"]
 
     # Make sure only the non-default variants are set.

lib/spack/spack/test/cmd/debug.py

@@ -6,7 +6,6 @@
 import os
 import os.path
 import platform
-import sys
 
 import pytest
 
@@ -17,7 +16,7 @@
 
 debug = SpackCommand("debug")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 @pytest.mark.db

lib/spack/spack/test/cmd/deprecate.py

@@ -3,8 +3,6 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
-import sys
-
 import pytest
 
 import spack.store
@@ -16,7 +14,7 @@
 deprecate = SpackCommand("deprecate")
 find = SpackCommand("find")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 def test_deprecate(mock_packages, mock_archive, mock_fetch, install_mockery):

lib/spack/spack/test/cmd/dev_build.py

@@ -4,7 +4,6 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
 import os
-import sys
 
 import pytest
 
@@ -18,7 +17,7 @@
 install = SpackCommand("install")
 env = SpackCommand("env")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 def test_dev_build_basics(tmpdir, mock_packages, install_mockery):

lib/spack/spack/test/cmd/develop.py

@@ -4,7 +4,6 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 import os
 import shutil
-import sys
 
 import pytest
 
@@ -17,7 +16,7 @@
 develop = SpackCommand("develop")
 env = SpackCommand("env")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 @pytest.mark.usefixtures("mutable_mock_env_path", "mock_packages", "mock_fetch", "config")

lib/spack/spack/test/cmd/diff.py

@@ -3,8 +3,6 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
-import sys
-
 import pytest
 
 import spack.cmd.diff
@@ -45,7 +43,7 @@ def test_diff_cmd(install_mockery, mock_fetch, mock_archive, mock_packages):
     assert ["hash", "mpileaks %s" % specB.dag_hash()] in c["b_not_a"]
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Not supported on Windows (yet)")
+@pytest.mark.not_on_windows("Not supported on Windows (yet)")
 def test_load_first(install_mockery, mock_fetch, mock_archive, mock_packages):
     """Test with and without the --first option"""
     install_cmd("mpileaks")

lib/spack/spack/test/cmd/env.py

@@ -8,7 +8,6 @@
 import os
 import pathlib
 import shutil
-import sys
 from argparse import Namespace
 
 import pytest
@@ -41,7 +40,7 @@
 pytestmark = [
     pytest.mark.usefixtures("mutable_mock_env_path", "config", "mutable_mock_repo"),
     pytest.mark.maybeslow,
-    pytest.mark.skipif(sys.platform == "win32", reason="Envs unsupported on Window"),
+    pytest.mark.not_on_windows("Envs unsupported on Window"),
 ]
 
 env = SpackCommand("env")

lib/spack/spack/test/cmd/extensions.py

@@ -3,7 +3,6 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
-import sys
 
 import pytest
 
@@ -23,7 +22,7 @@ def python_database(mock_packages, mutable_database):
     yield
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="All Fetchers Failed")
+@pytest.mark.not_on_windows("All Fetchers Failed")
 @pytest.mark.db
 def test_extensions(mock_packages, python_database, config, capsys):
     ext2 = Spec("py-extension2").concretized()

lib/spack/spack/test/cmd/external.py

@@ -212,7 +212,7 @@ def test_find_external_empty_default_manifest_dir(
     external("find")
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Can't chmod on Windows")
+@pytest.mark.not_on_windows("Can't chmod on Windows")
 @pytest.mark.skipif(getuid() == 0, reason="user is root")
 def test_find_external_manifest_with_bad_permissions(
     mutable_config,
@@ -399,7 +399,7 @@ def test_use_tags_for_detection(command_args, mock_executable, mutable_config, m
 
 
 @pytest.mark.regression("38733")
-@pytest.mark.skipif(sys.platform == "win32", reason="the test uses bash scripts")
+@pytest.mark.not_on_windows("the test uses bash scripts")
 def test_failures_in_scanning_do_not_result_in_an_error(
     mock_executable, monkeypatch, mutable_config
 ):

lib/spack/spack/test/cmd/find.py

@@ -332,7 +332,7 @@ def test_find_command_basic_usage(database):
     assert "mpileaks" in output
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="envirnment is not yet supported on windows")
+@pytest.mark.not_on_windows("envirnment is not yet supported on windows")
 @pytest.mark.regression("9875")
 def test_find_prefix_in_env(
     mutable_mock_env_path, install_mockery, mock_fetch, mock_packages, mock_archive, config

lib/spack/spack/test/cmd/gc.py

@@ -3,7 +3,6 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
-import sys
 
 import pytest
 
@@ -13,7 +12,7 @@
 
 gc = spack.main.SpackCommand("gc")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 @pytest.mark.db

lib/spack/spack/test/cmd/gpg.py

@@ -4,7 +4,6 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
 import os
-import sys
 
 import pytest
 
@@ -22,7 +21,7 @@
 bootstrap = SpackCommand("bootstrap")
 mirror = SpackCommand("mirror")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 # test gpg command detection

lib/spack/spack/test/cmd/install.py

@@ -7,8 +7,8 @@
 import filecmp
 import itertools
 import os
+import pathlib
 import re
-import sys
 import time
 
 import pytest
@@ -38,8 +38,6 @@
 buildcache = SpackCommand("buildcache")
 find = SpackCommand("find")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
-
 
 @pytest.fixture()
 def noop_install(monkeypatch):
@@ -204,7 +202,7 @@ def test_show_log_on_error(
     assert isinstance(install.error, spack.build_environment.ChildError)
     assert install.error.pkg.name == "build-error"
 
-    assert "==> Installing build-error" in out
+    assert "Installing build-error" in out
     assert "See build log for details:" in out
 
 
@@ -263,9 +261,9 @@ def test_install_commit(mock_git_version_info, install_mockery, mock_packages, m
 
     """
     repo_path, filename, commits = mock_git_version_info
-    monkeypatch.setattr(
-        spack.package_base.PackageBase, "git", "file://%s" % repo_path, raising=False
-    )
+    file_url = pathlib.Path(repo_path).as_uri()
+
+    monkeypatch.setattr(spack.package_base.PackageBase, "git", file_url, raising=False)
 
     # Use the earliest commit in the respository
     spec = Spec(f"git-test-commit@{commits[-1]}").concretized()
@@ -548,6 +546,7 @@ def test_cdash_report_concretization_error(
             assert any(x in content for x in expected_messages)
 
 
+@pytest.mark.not_on_windows("Windows log_output logs phase header out of order")
 @pytest.mark.disable_clean_stage_check
 def test_cdash_upload_build_error(tmpdir, mock_fetch, install_mockery, capfd):
     # capfd interferes with Spack's capturing
@@ -747,6 +746,7 @@ def test_install_deps_then_package(tmpdir, mock_fetch, install_mockery):
     assert os.path.exists(root.prefix)
 
 
+@pytest.mark.not_on_windows("Environment views not supported on windows. Revisit after #34701")
 @pytest.mark.regression("12002")
 def test_install_only_dependencies_in_env(
     tmpdir, mock_fetch, install_mockery, mutable_mock_env_path
@@ -896,7 +896,7 @@ def test_install_help_does_not_show_cdash_options(capsys):
         assert "CDash URL" not in captured.out
 
 
-def test_install_help_cdash(capsys):
+def test_install_help_cdash():
     """Make sure `spack install --help-cdash` describes CDash arguments"""
     install_cmd = SpackCommand("install")
     out = install_cmd("--help-cdash")
@@ -913,6 +913,7 @@ def test_cdash_auth_token(tmpdir, mock_fetch, install_mockery, capfd):
             assert "Using CDash auth token from environment" in out
 
 
+@pytest.mark.not_on_windows("Windows log_output logs phase header out of order")
 @pytest.mark.disable_clean_stage_check
 def test_cdash_configure_warning(tmpdir, mock_fetch, install_mockery, capfd):
     # capfd interferes with Spack's capturing of e.g., Build.xml output
@@ -938,6 +939,7 @@ def test_cdash_configure_warning(tmpdir, mock_fetch, install_mockery, capfd):
             assert "foo: No such file or directory" in content
 
 
+@pytest.mark.not_on_windows("ArchSpec gives test platform debian rather than windows")
 def test_compiler_bootstrap(
     install_mockery_mutable_config,
     mock_packages,
@@ -954,6 +956,7 @@ def test_compiler_bootstrap(
     install("a%gcc@=12.0")
 
 
+@pytest.mark.not_on_windows("Binary mirrors not supported on windows")
 def test_compiler_bootstrap_from_binary_mirror(
     install_mockery_mutable_config,
     mock_packages,
@@ -994,6 +997,7 @@ def test_compiler_bootstrap_from_binary_mirror(
     install("--no-cache", "--only", "package", "b%gcc@10.2.0")
 
 
+@pytest.mark.not_on_windows("ArchSpec gives test platform debian rather than windows")
 @pytest.mark.regression("16221")
 def test_compiler_bootstrap_already_installed(
     install_mockery_mutable_config,
@@ -1037,6 +1041,7 @@ def test_install_fails_no_args_suggests_env_activation(tmpdir):
     assert "using the `spack.yaml` in this directory" in output
 
 
+@pytest.mark.not_on_windows("Environment views not supported on windows. Revisit after #34701")
 def test_install_env_with_tests_all(
     tmpdir, mock_packages, mock_fetch, install_mockery, mutable_mock_env_path
 ):
@@ -1048,6 +1053,7 @@ def test_install_env_with_tests_all(
         assert os.path.exists(test_dep.prefix)
 
 
+@pytest.mark.not_on_windows("Environment views not supported on windows. Revisit after #34701")
 def test_install_env_with_tests_root(
     tmpdir, mock_packages, mock_fetch, install_mockery, mutable_mock_env_path
 ):
@@ -1059,6 +1065,7 @@ def test_install_env_with_tests_root(
         assert not os.path.exists(test_dep.prefix)
 
 
+@pytest.mark.not_on_windows("Environment views not supported on windows. Revisit after #34701")
 def test_install_empty_env(
     tmpdir, mock_packages, mock_fetch, install_mockery, mutable_mock_env_path
 ):
@@ -1072,6 +1079,7 @@ def test_install_empty_env(
     assert "no specs to install" in out
 
 
+@pytest.mark.not_on_windows("Windows logger I/O operation on closed file when install fails")
 @pytest.mark.disable_clean_stage_check
 @pytest.mark.parametrize(
     "name,method",
@@ -1095,6 +1103,7 @@ def test_installation_fail_tests(install_mockery, mock_fetch, name, method):
     assert "See test log for details" in output
 
 
+@pytest.mark.not_on_windows("Buildcache not supported on windows")
 def test_install_use_buildcache(
     capsys,
     mock_packages,
@@ -1172,6 +1181,7 @@ def install_use_buildcache(opt):
             install_use_buildcache(opt)
 
 
+@pytest.mark.not_on_windows("Windows logger I/O operation on closed file when install fails")
 @pytest.mark.regression("34006")
 @pytest.mark.disable_clean_stage_check
 def test_padded_install_runtests_root(install_mockery_mutable_config, mock_fetch):

lib/spack/spack/test/cmd/license.py

@@ -5,7 +5,6 @@
 
 import os.path
 import re
-import sys
 
 import pytest
 
@@ -17,7 +16,7 @@
 
 license = SpackCommand("license")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 def test_list_files():

lib/spack/spack/test/cmd/load.py

@@ -4,7 +4,6 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 import os
 import re
-import sys
 
 import pytest
 
@@ -17,7 +16,7 @@
 install = SpackCommand("install")
 location = SpackCommand("location")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 def test_manpath_trailing_colon(

lib/spack/spack/test/cmd/location.py

@@ -5,7 +5,6 @@
 
 import os
 import shutil
-import sys
 
 import pytest
 
@@ -19,7 +18,7 @@
 # Everything here uses (or can use) the mock config and database.
 pytestmark = [
     pytest.mark.usefixtures("config", "database"),
-    pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows"),
+    pytest.mark.not_on_windows("does not run on windows"),
 ]
 # location prints out "locations of packages and spack directories"
 location = SpackCommand("location")

lib/spack/spack/test/cmd/mirror.py

@@ -4,7 +4,6 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
 import os
-import sys
 
 import pytest
 
@@ -23,7 +22,7 @@
 buildcache = SpackCommand("buildcache")
 uninstall = SpackCommand("uninstall")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 @pytest.mark.disable_clean_stage_check

lib/spack/spack/test/cmd/module.py

@@ -5,7 +5,6 @@
 
 import os.path
 import re
-import sys
 
 import pytest
 
@@ -16,7 +15,7 @@
 
 module = spack.main.SpackCommand("module")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 #: make sure module files are generated for all the tests here

lib/spack/spack/test/cmd/pkg.py

@@ -5,7 +5,6 @@
 
 import re
 import shutil
-import sys
 
 import pytest
 
@@ -133,7 +132,7 @@ def test_pkg_add(git, mock_pkg_git_repo):
         pkg("add", "does-not-exist")
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="stdout format conflict")
+@pytest.mark.not_on_windows("stdout format conflict")
 def test_pkg_list(mock_pkg_git_repo, mock_pkg_names):
     out = split(pkg("list", "HEAD^^"))
     assert sorted(mock_pkg_names) == sorted(out)
@@ -149,7 +148,7 @@ def test_pkg_list(mock_pkg_git_repo, mock_pkg_names):
     assert sorted(mock_pkg_names) == sorted(out)
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="stdout format conflict")
+@pytest.mark.not_on_windows("stdout format conflict")
 def test_pkg_diff(mock_pkg_git_repo, mock_pkg_names):
     out = split(pkg("diff", "HEAD^^", "HEAD^"))
     assert out == ["HEAD^:", "pkg-a", "pkg-b", "pkg-c"]
@@ -161,7 +160,7 @@ def test_pkg_diff(mock_pkg_git_repo, mock_pkg_names):
     assert out == ["HEAD^:", "pkg-c", "HEAD:", "pkg-d"]
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="stdout format conflict")
+@pytest.mark.not_on_windows("stdout format conflict")
 def test_pkg_added(mock_pkg_git_repo):
     out = split(pkg("added", "HEAD^^", "HEAD^"))
     assert ["pkg-a", "pkg-b", "pkg-c"] == out
@@ -176,7 +175,7 @@ def test_pkg_added(mock_pkg_git_repo):
     assert out == []
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="stdout format conflict")
+@pytest.mark.not_on_windows("stdout format conflict")
 def test_pkg_removed(mock_pkg_git_repo):
     out = split(pkg("removed", "HEAD^^", "HEAD^"))
     assert out == []
@@ -188,7 +187,7 @@ def test_pkg_removed(mock_pkg_git_repo):
     assert out == ["pkg-c"]
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="stdout format conflict")
+@pytest.mark.not_on_windows("stdout format conflict")
 def test_pkg_changed(mock_pkg_git_repo):
     out = split(pkg("changed", "HEAD^^", "HEAD^"))
     assert out == []

lib/spack/spack/test/cmd/providers.py

@@ -4,17 +4,13 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
 
-import sys
-
 import pytest
 
 from spack.main import SpackCommand
 
 providers = SpackCommand("providers")
 
-pytestmark = pytest.mark.skipif(
-    sys.platform == "win32", reason="Providers not currently supported on Windows"
-)
+pytestmark = pytest.mark.not_on_windows("Providers not currently supported on Windows")
 
 
 @pytest.mark.parametrize(

lib/spack/spack/test/cmd/reindex.py

@@ -3,7 +3,6 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 import os
-import sys
 
 import pytest
 
@@ -14,7 +13,7 @@
 deprecate = SpackCommand("deprecate")
 reindex = SpackCommand("reindex")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 def test_reindex_basic(mock_packages, mock_archive, mock_fetch, install_mockery):

lib/spack/spack/test/cmd/spec.py

@@ -32,6 +32,7 @@ def test_spec():
     assert "mpich@3.0.4" in output
 
 
+@pytest.mark.only_clingo("Known failure of the original concretizer")
 def test_spec_concretizer_args(mutable_config, mutable_database):
     """End-to-end test of CLI concretizer prefs.
 
@@ -39,9 +40,6 @@ def test_spec_concretizer_args(mutable_config, mutable_database):
     options to `solver.py`, and that config options are not
     lost along the way.
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.xfail("Known failure of the original concretizer")
-
     # remove two non-preferred mpileaks installations
     # so that reuse will pick up the zmpi one
     uninstall = SpackCommand("uninstall")

lib/spack/spack/test/cmd/stage.py

@@ -4,7 +4,6 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
 import os
-import sys
 
 import pytest
 
@@ -23,7 +22,7 @@
 pytestmark = pytest.mark.usefixtures("install_mockery", "mock_packages")
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="not implemented on windows")
+@pytest.mark.not_on_windows("not implemented on windows")
 @pytest.mark.disable_clean_stage_check
 def test_stage_spec(monkeypatch):
     """Verify that staging specs works."""
@@ -52,7 +51,7 @@ def fake_stage(pkg, mirror_only=False):
     return expected_path
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="PermissionError")
+@pytest.mark.not_on_windows("PermissionError")
 def test_stage_path(check_stage_path):
     """Verify that --path only works with single specs."""
     stage("--path={0}".format(check_stage_path), "trivial-install-test-package")
@@ -64,7 +63,7 @@ def test_stage_path_errors_multiple_specs(check_stage_path):
         stage(f"--path={check_stage_path}", "trivial-install-test-package", "mpileaks")
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="not implemented on windows")
+@pytest.mark.not_on_windows("not implemented on windows")
 @pytest.mark.disable_clean_stage_check
 def test_stage_with_env_outside_env(mutable_mock_env_path, monkeypatch):
     """Verify that stage concretizes specs not in environment instead of erroring."""
@@ -83,7 +82,7 @@ def fake_stage(pkg, mirror_only=False):
         stage("trivial-install-test-package")
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="not implemented on windows")
+@pytest.mark.not_on_windows("not implemented on windows")
 @pytest.mark.disable_clean_stage_check
 def test_stage_with_env_inside_env(mutable_mock_env_path, monkeypatch):
     """Verify that stage filters specs in environment instead of reconcretizing."""
@@ -102,7 +101,7 @@ def fake_stage(pkg, mirror_only=False):
         stage("mpileaks")
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="not implemented on windows")
+@pytest.mark.not_on_windows("not implemented on windows")
 @pytest.mark.disable_clean_stage_check
 def test_stage_full_env(mutable_mock_env_path, monkeypatch):
     """Verify that stage filters specs in environment."""

lib/spack/spack/test/cmd/test.py

@@ -5,7 +5,6 @@
 
 import argparse
 import os
-import sys
 
 import pytest
 
@@ -22,7 +21,7 @@
 install = SpackCommand("install")
 spack_test = SpackCommand("test")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 def test_test_package_not_installed(

lib/spack/spack/test/cmd/undevelop.py

@@ -3,7 +3,6 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
-import sys
 
 import pytest
 
@@ -15,7 +14,7 @@
 env = SpackCommand("env")
 concretize = SpackCommand("concretize")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 def test_undevelop(tmpdir, config, mock_packages, mutable_mock_env_path):

lib/spack/spack/test/cmd/uninstall.py

@@ -3,7 +3,6 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
-import sys
 
 import pytest
 
@@ -206,7 +205,7 @@ def _warn(*args, **kwargs):
 
 # Note: I want to use https://docs.pytest.org/en/7.1.x/how-to/skipping.html#skip-all-test-functions-of-a-class-or-module
 # the style formatter insists on separating these two lines.
-@pytest.mark.skipif(sys.platform == "win32", reason="Envs unsupported on Windows")
+@pytest.mark.not_on_windows("Envs unsupported on Windows")
 class TestUninstallFromEnv:
     """Tests an installation with two environments e1 and e2, which each have
     shared package installations:

lib/spack/spack/test/cmd/view.py

@@ -4,7 +4,6 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
 import os.path
-import sys
 
 import pytest
 
@@ -16,7 +15,7 @@
 install = SpackCommand("install")
 view = SpackCommand("view")
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="does not run on windows")
+pytestmark = pytest.mark.not_on_windows("does not run on windows")
 
 
 def create_projection_file(tmpdir, projection):

lib/spack/spack/test/compilers/basics.py

@@ -4,7 +4,6 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 """Test basic behavior of compilers in Spack"""
 import os
-import sys
 from copy import copy
 
 import pytest
@@ -192,7 +191,7 @@ def call_compiler(exe, *args, **kwargs):
     return no_flag_output
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Not supported on Windows (yet)")
+@pytest.mark.not_on_windows("Not supported on Windows (yet)")
 @pytest.mark.parametrize(
     "exe,flagname",
     [
@@ -248,7 +247,7 @@ def test_get_compiler_link_paths_no_verbose_flag():
     assert dirs == []
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Not supported on Windows (yet)")
+@pytest.mark.not_on_windows("Not supported on Windows (yet)")
 @pytest.mark.enable_compiler_link_paths
 def test_get_compiler_link_paths_load_env(working_env, monkeypatch, tmpdir):
     gcc = str(tmpdir.join("gcc"))
@@ -693,7 +692,7 @@ def test_raising_if_compiler_target_is_over_specific(config):
             spack.compilers.get_compilers(cfg, spack.spec.CompilerSpec("gcc@9.0.1"), arch_spec)
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Not supported on Windows (yet)")
+@pytest.mark.not_on_windows("Not supported on Windows (yet)")
 def test_compiler_get_real_version(working_env, monkeypatch, tmpdir):
     # Test variables
     test_version = "2.2.2"
@@ -796,9 +795,7 @@ def _call(*args, **kwargs):
         assert "SPACK_TEST_CMP_ON" not in os.environ
 
 
-@pytest.mark.skipif(
-    sys.platform == "win32", reason="Bash scripting unsupported on Windows (for now)"
-)
+@pytest.mark.not_on_windows("Bash scripting unsupported on Windows (for now)")
 def test_compiler_flags_use_real_version(working_env, monkeypatch, tmpdir):
     # Create compiler
     gcc = str(tmpdir.join("gcc"))

lib/spack/spack/test/compilers/detection.py

@@ -4,7 +4,6 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 """Test detection of compiler version"""
 import os
-import sys
 
 import pytest
 
@@ -414,7 +413,7 @@ def test_xl_version_detection(version_str, expected_version):
     assert version == expected_version
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Not supported on Windows (yet)")
+@pytest.mark.not_on_windows("Not supported on Windows (yet)")
 @pytest.mark.parametrize(
     "compiler,version",
     [

lib/spack/spack/test/concretize.py

@@ -152,7 +152,7 @@ class Root(Package):
     version("1.0", sha256="abcde")
     depends_on("changing")
 
-    conflicts("changing~foo")
+    conflicts("^changing~foo")
 """
     packages_dir.join("root", "package.py").write(root_pkg_str, ensure=True)
 
@@ -353,9 +353,8 @@ def test_concretize_compiler_flag_propagate(self):
 
         assert spec.satisfies("^openblas cflags='-g'")
 
-    @pytest.mark.skipif(
-        os.environ.get("SPACK_TEST_SOLVER") == "original",
-        reason="Optional compiler propagation isn't deprecated for original concretizer",
+    @pytest.mark.only_clingo(
+        "Optional compiler propagation isn't deprecated for original concretizer"
     )
     def test_concretize_compiler_flag_does_not_propagate(self):
         spec = Spec("hypre cflags='-g' ^openblas")
@@ -363,9 +362,8 @@ def test_concretize_compiler_flag_does_not_propagate(self):
 
         assert not spec.satisfies("^openblas cflags='-g'")
 
-    @pytest.mark.skipif(
-        os.environ.get("SPACK_TEST_SOLVER") == "original",
-        reason="Optional compiler propagation isn't deprecated for original concretizer",
+    @pytest.mark.only_clingo(
+        "Optional compiler propagation isn't deprecated for original concretizer"
     )
     def test_concretize_propagate_compiler_flag_not_passed_to_dependent(self):
         spec = Spec("hypre cflags=='-g' ^openblas cflags='-O3'")
@@ -394,14 +392,12 @@ def test_architecture_inheritance(self):
         spec.concretize()
         assert spec["cmake"].architecture == spec.architecture
 
+    @pytest.mark.only_clingo("Fixing the parser broke this test for the original concretizer")
     def test_architecture_deep_inheritance(self, mock_targets):
         """Make sure that indirect dependencies receive architecture
         information from the root even when partial architecture information
         is provided by an intermediate dependency.
         """
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Fixing the parser broke this test for the original concretizer.")
-
         spec_str = "mpileaks %gcc@4.5.0 os=CNL target=nocona" " ^dyninst os=CNL ^callpath os=CNL"
         spec = Spec(spec_str).concretized()
         for s in spec.traverse(root=False):
@@ -457,9 +453,8 @@ def test_concretize_two_virtuals_with_dual_provider_and_a_conflict(self):
         with pytest.raises(spack.error.SpackError):
             s.concretize()
 
-    @pytest.mark.skipif(
-        os.environ.get("SPACK_TEST_SOLVER") == "original",
-        reason="Optional compiler propagation isn't deprecated for original concretizer",
+    @pytest.mark.only_clingo(
+        "Optional compiler propagation isn't deprecated for original concretizer"
     )
     def test_concretize_propagate_disabled_variant(self):
         """Test a package variant value was passed from its parent."""
@@ -619,10 +614,8 @@ def test_conflicts_in_spec(self, conflict_spec):
         with pytest.raises(spack.error.SpackError):
             s.concretize()
 
+    @pytest.mark.only_clingo("Testing debug statements specific to new concretizer")
     def test_conflicts_show_cores(self, conflict_spec, monkeypatch):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Testing debug statements specific to new concretizer")
-
         s = Spec(conflict_spec)
         with pytest.raises(spack.error.SpackError) as e:
             s.concretize()
@@ -742,7 +735,7 @@ def test_noversion_pkg(self, spec):
         with pytest.raises(spack.error.SpackError):
             Spec(spec).concretized()
 
-    @pytest.mark.skipif(sys.platform == "win32", reason="Not supported on Windows (yet)")
+    @pytest.mark.not_on_windows("Not supported on Windows (yet)")
     # Include targets to prevent regression on 20537
     @pytest.mark.parametrize(
         "spec, best_achievable",
@@ -795,10 +788,8 @@ def test_concretize_anonymous_dep(self, spec_str):
             ("bowtie@1.2.2 os=redhat6", "%gcc@11.1.0"),
         ],
     )
+    @pytest.mark.only_clingo("Original concretizer cannot work around conflicts")
     def test_compiler_conflicts_in_package_py(self, spec_str, expected_str):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Original concretizer cannot work around conflicts")
-
         s = Spec(spec_str).concretized()
         assert s.satisfies(expected_str)
 
@@ -902,10 +893,8 @@ def test_patching_dependencies(self, spec_str, patched_deps):
             ("quantum-espresso~veritas", ["^libelf@0.8.13"]),
         ],
     )
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_working_around_conflicting_defaults(self, spec_str, expected):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known failure of the original concretizer")
-
         s = Spec(spec_str).concretized()
 
         assert s.concrete
@@ -917,10 +906,8 @@ def test_working_around_conflicting_defaults(self, spec_str, expected):
         "spec_str,expected",
         [("cmake", ["%clang"]), ("cmake %gcc", ["%gcc"]), ("cmake %clang", ["%clang"])],
     )
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_external_package_and_compiler_preferences(self, spec_str, expected):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known failure of the original concretizer")
-
         packages_yaml = {
             "all": {"compiler": ["clang", "gcc"]},
             "cmake": {
@@ -936,14 +923,12 @@ def test_external_package_and_compiler_preferences(self, spec_str, expected):
             assert s.satisfies(condition)
 
     @pytest.mark.regression("5651")
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_package_with_constraint_not_met_by_external(self):
         """Check that if we have an external package A at version X.Y in
         packages.yaml, but our spec doesn't allow X.Y as a version, then
         a new version of A is built that meets the requirements.
         """
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known failure of the original concretizer")
-
         packages_yaml = {"libelf": {"externals": [{"spec": "libelf@0.8.13", "prefix": "/usr"}]}}
         spack.config.set("packages", packages_yaml)
 
@@ -953,10 +938,8 @@ def test_package_with_constraint_not_met_by_external(self):
         assert not s["libelf"].external
 
     @pytest.mark.regression("9744")
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_cumulative_version_ranges_with_different_length(self):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known failure of the original concretizer")
-
         s = Spec("cumulative-vrange-root").concretized()
         assert s.concrete
         assert s.satisfies("^cumulative-vrange-bottom@2.2")
@@ -983,10 +966,8 @@ def test_dependency_conditional_on_another_dependency_state(self):
     @pytest.mark.parametrize(
         "spec_str,expected", [("cmake %gcc", "%gcc"), ("cmake %clang", "%clang")]
     )
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_compiler_constraint_with_external_package(self, spec_str, expected):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known failure of the original concretizer")
-
         packages_yaml = {
             "cmake": {"externals": [{"spec": "cmake@3.4.3", "prefix": "/usr"}], "buildable": False}
         }
@@ -1035,10 +1016,8 @@ def test_compiler_in_nonbuildable_external_package(
         assert s.satisfies(expected)
         assert "external-common-perl" not in [d.name for d in s.dependencies()]
 
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_external_packages_have_consistent_hash(self):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("This tests needs the ASP-based concretizer")
-
         s, t = Spec("externaltool"), Spec("externaltool")
         s._old_concretize(), t._new_concretize()
 
@@ -1062,10 +1041,8 @@ def test_transitive_conditional_virtual_dependency(self):
         assert "externalvirtual" in s
 
     @pytest.mark.regression("20040")
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_conditional_provides_or_depends_on(self):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known failure of the original concretizer")
-
         # Check that we can concretize correctly a spec that can either
         # provide a virtual or depend on it based on the value of a variant
         s = Spec("conditional-provider +disable-v1").concretized()
@@ -1103,10 +1080,8 @@ def test_activating_test_dependencies(self, spec_str, tests_arg, with_dep, witho
             assert not node.dependencies(deptype="test"), msg.format(pkg_name)
 
     @pytest.mark.regression("20019")
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_compiler_match_is_preferred_to_newer_version(self):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known failure of the original concretizer")
-
         # This spec depends on openblas. Openblas has a conflict
         # that doesn't allow newer versions with gcc@4.4.0. Check
         # that an old version of openblas is selected, rather than
@@ -1122,9 +1097,8 @@ def test_target_ranges_in_conflicts(self):
         with pytest.raises(spack.error.SpackError):
             Spec("impossible-concretization").concretized()
 
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_target_compatibility(self):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known failure of the original concretizer")
         with pytest.raises(spack.error.SpackError):
             Spec("libdwarf target=x86_64 ^libelf target=x86_64_v2").concretized()
 
@@ -1140,10 +1114,8 @@ def test_variant_not_default(self):
         assert "+foo+bar+baz" in d
 
     @pytest.mark.regression("20055")
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_custom_compiler_version(self):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known failure of the original concretizer")
-
         s = Spec("a %gcc@10foo os=redhat6").concretized()
         assert "%gcc@10foo" in s
 
@@ -1240,12 +1212,10 @@ def mock_fn(*args, **kwargs):
             {"add_variant": True, "delete_variant": True},
         ],
     )
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_reuse_installed_packages_when_package_def_changes(
         self, context, mutable_database, repo_with_changing_recipe
     ):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known failure of the original concretizer")
-
         # Install a spec
         root = Spec("root").concretized()
         dependency = root["changing"].copy()
@@ -1269,10 +1239,8 @@ def test_reuse_installed_packages_when_package_def_changes(
         # Structure and package hash will be different without reuse
         assert root.dag_hash() != new_root_without_reuse.dag_hash()
 
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_reuse_with_flags(self, mutable_database, mutable_config):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Original concretizer does not reuse")
-
         spack.config.set("concretizer:reuse", True)
         spec = Spec("a cflags=-g cxxflags=-g").concretized()
         spack.store.STORE.db.add(spec, None)
@@ -1292,10 +1260,8 @@ def test_concretization_of_test_dependencies(self):
     @pytest.mark.parametrize(
         "spec_str", ["wrong-variant-in-conflicts", "wrong-variant-in-depends-on"]
     )
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_error_message_for_inconsistent_variants(self, spec_str):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known failure of the original concretizer")
-
         s = Spec(spec_str)
         with pytest.raises(RuntimeError, match="not found in package"):
             s.concretize()
@@ -1392,12 +1358,9 @@ def test_multivalued_variants_from_cli(self, spec_str, expected_dict):
             ("deprecated-versions@1.1.0", ["deprecated-versions@1.1.0"]),
         ],
     )
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_deprecated_versions_not_selected(self, spec_str, expected):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known failure of the original concretizer")
-
         s = Spec(spec_str).concretized()
-
         for abstract_spec in expected:
             assert abstract_spec in s
 
@@ -1456,12 +1419,10 @@ def test_non_default_provider_of_multiple_virtuals(self):
         "spec_str,expect_installed",
         [("mpich", True), ("mpich+debug", False), ("mpich~debug", True)],
     )
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_concrete_specs_are_not_modified_on_reuse(
         self, mutable_database, spec_str, expect_installed, config
     ):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Original concretizer cannot reuse specs")
-
         # Test the internal consistency of solve + DAG reconstruction
         # when reused specs are added to the mix. This prevents things
         # like additional constraints being added to concrete specs in
@@ -1472,10 +1433,8 @@ def test_concrete_specs_are_not_modified_on_reuse(
         assert s.satisfies(spec_str)
 
     @pytest.mark.regression("26721,19736")
+    @pytest.mark.only_clingo("Original concretizer cannot use sticky variants")
     def test_sticky_variant_in_package(self):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Original concretizer cannot use sticky variants")
-
         # Here we test that a sticky variant cannot be changed from its default value
         # by the ASP solver if not set explicitly. The package used in the test needs
         # to have +allow-gcc set to be concretized with %gcc and clingo is not allowed
@@ -1489,10 +1448,8 @@ def test_sticky_variant_in_package(self):
         s = Spec("sticky-variant %clang").concretized()
         assert s.satisfies("%clang") and s.satisfies("~allow-gcc")
 
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_do_not_invent_new_concrete_versions_unless_necessary(self):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Original concretizer doesn't resolve concrete versions to known ones")
-
         # ensure we select a known satisfying version rather than creating
         # a new '2.7' version.
         assert ver("=2.7.11") == Spec("python@2.7").concretized().version
@@ -1513,30 +1470,24 @@ def test_do_not_invent_new_concrete_versions_unless_necessary(self):
             ("conditional-values-in-variant foo=foo", True),
         ],
     )
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_conditional_values_in_variants(self, spec_str, valid):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Original concretizer doesn't resolve conditional values in variants")
-
         s = Spec(spec_str)
         raises = pytest.raises((RuntimeError, spack.error.UnsatisfiableSpecError))
         with llnl.util.lang.nullcontext() if valid else raises:
             s.concretize()
 
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_conditional_values_in_conditional_variant(self):
         """Test that conditional variants play well with conditional possible values"""
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Original concretizer doesn't resolve conditional values in variants")
-
         s = Spec("conditional-values-in-variant@1.50.0").concretized()
         assert "cxxstd" not in s.variants
 
         s = Spec("conditional-values-in-variant@1.60.0").concretized()
         assert "cxxstd" in s.variants
 
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_target_granularity(self):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Original concretizer cannot account for target granularity")
-
         # The test architecture uses core2 as the default target. Check that when
         # we configure Spack for "generic" granularity we concretize for x86_64
         default_target = spack.platforms.test.Test.default
@@ -1546,10 +1497,8 @@ def test_target_granularity(self):
         with spack.config.override("concretizer:targets", {"granularity": "generic"}):
             assert s.concretized().satisfies("target=%s" % generic_target)
 
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_host_compatible_concretization(self):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Original concretizer cannot account for host compatibility")
-
         # Check that after setting "host_compatible" to false we cannot concretize.
         # Here we use "k10" to set a target non-compatible with the current host
         # to avoid a lot of boilerplate when mocking the test platform. The issue
@@ -1561,10 +1510,8 @@ def test_host_compatible_concretization(self):
             with pytest.raises(spack.error.SpackError):
                 s.concretized()
 
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_add_microarchitectures_on_explicit_request(self):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Original concretizer cannot account for host compatibility")
-
         # Check that if we consider only "generic" targets, we can still solve for
         # specific microarchitectures on explicit requests
         with spack.config.override("concretizer:targets", {"granularity": "generic"}):
@@ -1572,13 +1519,11 @@ def test_add_microarchitectures_on_explicit_request(self):
         assert s.satisfies("target=k10")
 
     @pytest.mark.regression("29201")
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_delete_version_and_reuse(self, mutable_database, repo_with_changing_recipe):
         """Test that we can reuse installed specs with versions not
         declared in package.py
         """
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known failure of the original concretizer")
-
         root = Spec("root").concretized()
         root.package.do_install(fake=True, explicit=True)
         repo_with_changing_recipe.change({"delete_version": True})
@@ -1589,17 +1534,15 @@ def test_delete_version_and_reuse(self, mutable_database, repo_with_changing_rec
         assert root.dag_hash() == new_root.dag_hash()
 
     @pytest.mark.regression("29201")
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_installed_version_is_selected_only_for_reuse(
         self, mutable_database, repo_with_changing_recipe
     ):
         """Test that a version coming from an installed spec is a possible
         version only for reuse
         """
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known failure of the original concretizer")
-
         # Install a dependency that cannot be reused with "root"
-        # because of a conflict a variant, then delete its version
+        # because of a conflict in a variant, then delete its version
         dependency = Spec("changing@1.0~foo").concretized()
         dependency.package.do_install(fake=True, explicit=True)
         repo_with_changing_recipe.change({"delete_version": True})
@@ -1653,12 +1596,10 @@ def test_reuse_with_unknown_package_dont_raise(self, tmpdir, monkeypatch):
             (["mpi", "mpich"], 1),
         ],
     )
+    @pytest.mark.only_clingo("Original concretizer cannot concretize in rounds")
     def test_best_effort_coconcretize(self, specs, expected):
         import spack.solver.asp
 
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Original concretizer cannot concretize in rounds")
-
         specs = [Spec(s) for s in specs]
         solver = spack.solver.asp.Solver()
         solver.reuse = False
@@ -1699,13 +1640,11 @@ def test_best_effort_coconcretize(self, specs, expected):
             (["hdf5+mpi", "zmpi", "mpich"], "mpich", 2),
         ],
     )
+    @pytest.mark.only_clingo("Original concretizer cannot concretize in rounds")
     def test_best_effort_coconcretize_preferences(self, specs, expected_spec, occurances):
         """Test package preferences during coconcretization."""
         import spack.solver.asp
 
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Original concretizer cannot concretize in rounds")
-
         specs = [Spec(s) for s in specs]
         solver = spack.solver.asp.Solver()
         solver.reuse = False
@@ -1719,20 +1658,16 @@ def test_best_effort_coconcretize_preferences(self, specs, expected_spec, occura
                 counter += 1
         assert counter == occurances, concrete_specs
 
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_coconcretize_reuse_and_virtuals(self):
         import spack.solver.asp
 
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Original concretizer cannot reuse")
-
         reusable_specs = []
         for s in ["mpileaks ^mpich", "zmpi"]:
             reusable_specs.extend(Spec(s).concretized().traverse(root=True))
 
         root_specs = [Spec("mpileaks"), Spec("zmpi")]
 
-        import spack.solver.asp
-
         with spack.config.override("concretizer:reuse", True):
             solver = spack.solver.asp.Solver()
             setup = spack.solver.asp.SpackSolverSetup()
@@ -1742,15 +1677,13 @@ def test_coconcretize_reuse_and_virtuals(self):
             assert "zmpi" in spec
 
     @pytest.mark.regression("30864")
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_misleading_error_message_on_version(self, mutable_database):
         # For this bug to be triggered we need a reusable dependency
         # that is not optimal in terms of optimization scores.
         # We pick an old version of "b"
         import spack.solver.asp
 
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Original concretizer cannot reuse")
-
         reusable_specs = [Spec("non-existing-conditional-dep@1.0").concretized()]
         root_spec = Spec("non-existing-conditional-dep@2.0")
 
@@ -1763,13 +1696,11 @@ def test_misleading_error_message_on_version(self, mutable_database):
                 solver.driver.solve(setup, [root_spec], reuse=reusable_specs)
 
     @pytest.mark.regression("31148")
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_version_weight_and_provenance(self):
         """Test package preferences during coconcretization."""
         import spack.solver.asp
 
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Original concretizer cannot reuse")
-
         reusable_specs = [Spec(spec_str).concretized() for spec_str in ("b@0.9", "b@1.0")]
         root_spec = Spec("a foobar=bar")
 
@@ -1799,12 +1730,10 @@ def test_version_weight_and_provenance(self):
             assert result_spec.satisfies("^b@1.0")
 
     @pytest.mark.regression("31169")
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_not_reusing_incompatible_os_or_compiler(self):
         import spack.solver.asp
 
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Original concretizer cannot reuse")
-
         root_spec = Spec("b")
         s = root_spec.concretized()
         wrong_compiler, wrong_os = s.copy(), s.copy()
@@ -1826,9 +1755,8 @@ def test_git_hash_assigned_version_is_preferred(self):
         assert hash in str(c)
 
     @pytest.mark.parametrize("git_ref", ("a" * 40, "0.2.15", "main"))
+    @pytest.mark.only_clingo("Original concretizer cannot account for git hashes")
     def test_git_ref_version_is_equivalent_to_specified_version(self, git_ref):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Original concretizer cannot account for git hashes")
         s = Spec("develop-branch-version@git.%s=develop" % git_ref)
         c = s.concretized()
         assert git_ref in str(c)
@@ -1837,21 +1765,17 @@ def test_git_ref_version_is_equivalent_to_specified_version(self, git_ref):
         assert s.satisfies("@0.1:")
 
     @pytest.mark.parametrize("git_ref", ("a" * 40, "0.2.15", "fbranch"))
+    @pytest.mark.only_clingo("Original concretizer cannot account for git hashes")
     def test_git_ref_version_succeeds_with_unknown_version(self, git_ref):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("Original concretizer cannot account for git hashes")
         # main is not defined in the package.py for this file
         s = Spec("develop-branch-version@git.%s=main" % git_ref)
         s.concretize()
         assert s.satisfies("develop-branch-version@main")
 
     @pytest.mark.regression("31484")
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_installed_externals_are_reused(self, mutable_database, repo_with_changing_recipe):
         """Test that external specs that are in the DB can be reused."""
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Use case not supported by the original concretizer")
-
-        # Configuration to be added to packages.yaml
         external_conf = {
             "changing": {
                 "buildable": False,
@@ -1879,12 +1803,9 @@ def test_installed_externals_are_reused(self, mutable_database, repo_with_changi
         assert external3.dag_hash() == external1.dag_hash()
 
     @pytest.mark.regression("31484")
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_user_can_select_externals_with_require(self, mutable_database):
         """Test that users have means to select an external even in presence of reusable specs."""
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Use case not supported by the original concretizer")
-
-        # Configuration to be added to packages.yaml
         external_conf = {
             "mpi": {"buildable": False},
             "multi-provider-mpi": {
@@ -1911,13 +1832,11 @@ def test_user_can_select_externals_with_require(self, mutable_database):
             assert mpi_spec.name == "multi-provider-mpi"
 
     @pytest.mark.regression("31484")
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_installed_specs_disregard_conflicts(self, mutable_database, monkeypatch):
         """Test that installed specs do not trigger conflicts. This covers for the rare case
         where a conflict is added on a package after a spec matching the conflict was installed.
         """
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Use case not supported by the original concretizer")
-
         # Add a conflict to "mpich" that match an already installed "mpich~debug"
         pkg_cls = spack.repo.PATH.get_pkg_class("mpich")
         monkeypatch.setitem(pkg_cls.conflicts, "~debug", [(Spec(), None)])
@@ -1933,11 +1852,9 @@ def test_installed_specs_disregard_conflicts(self, mutable_database, monkeypatch
             assert s.satisfies("~debug")
 
     @pytest.mark.regression("32471")
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_require_targets_are_allowed(self, mutable_database):
         """Test that users can set target constraints under the require attribute."""
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Use case not supported by the original concretizer")
-
         # Configuration to be added to packages.yaml
         external_conf = {"all": {"require": "target=%s" % spack.platforms.test.Test.front_end}}
         spack.config.set("packages", external_conf)
@@ -2125,7 +2042,7 @@ def test_compiler_match_constraints_when_selected(self):
         assert s.compiler.version == ver("=11.1.0"), s
 
     @pytest.mark.regression("36339")
-    @pytest.mark.skipif(sys.platform == "win32", reason="Not supported on Windows")
+    @pytest.mark.not_on_windows("Not supported on Windows")
     def test_compiler_with_custom_non_numeric_version(self, mock_executable):
         """Test that, when a compiler has a completely made up version, we can use its
         'real version' to detect targets and don't raise during concretization.
@@ -2181,3 +2098,98 @@ def test_virtuals_are_annotated_on_edges(self, spec_str, default_mock_concretiza
         assert len(edges) == 1 and edges[0].virtuals == ("mpi",)
         edges = spec.edges_to_dependencies(name="callpath")
         assert len(edges) == 1 and edges[0].virtuals == ()
+
+
+@pytest.fixture()
+def duplicates_test_repository():
+    builder_test_path = os.path.join(spack.paths.repos_path, "duplicates.test")
+    with spack.repo.use_repositories(builder_test_path) as mock_repo:
+        yield mock_repo
+
+
+@pytest.mark.usefixtures("mutable_config", "duplicates_test_repository")
+class TestConcretizeSeparately:
+    @pytest.mark.parametrize("strategy", ["minimal", "full"])
+    @pytest.mark.skipif(
+        os.environ.get("SPACK_TEST_SOLVER") == "original",
+        reason="Not supported by the original concretizer",
+    )
+    def test_two_gmake(self, strategy):
+        """Tests that we can concretize a spec with nodes using the same build
+        dependency pinned at different versions.
+
+        o hdf5@1.0
+        |\
+        o | pinned-gmake@1.0
+        o | gmake@3.0
+         /
+        o gmake@4.1
+
+        """
+        spack.config.CONFIG.set("concretizer:duplicates:strategy", strategy)
+        s = Spec("hdf5").concretized()
+
+        # Check that hdf5 depends on gmake@=4.1
+        hdf5_gmake = s["hdf5"].dependencies(name="gmake", deptype="build")
+        assert len(hdf5_gmake) == 1 and hdf5_gmake[0].satisfies("@=4.1")
+
+        # Check that pinned-gmake depends on gmake@=3.0
+        pinned_gmake = s["pinned-gmake"].dependencies(name="gmake", deptype="build")
+        assert len(pinned_gmake) == 1 and pinned_gmake[0].satisfies("@=3.0")
+
+    @pytest.mark.parametrize("strategy", ["minimal", "full"])
+    @pytest.mark.skipif(
+        os.environ.get("SPACK_TEST_SOLVER") == "original",
+        reason="Not supported by the original concretizer",
+    )
+    def test_two_setuptools(self, strategy):
+        """Tests that we can concretize separate build dependencies, when we are dealing
+        with extensions.
+
+        o py-shapely@1.25.0
+        |\
+        | |\
+        | o | py-setuptools@60
+        |/ /
+        | o py-numpy@1.25.0
+        |/|
+        | |\
+        | o | py-setuptools@59
+        |/ /
+        o | python@3.11.2
+        o | gmake@3.0
+         /
+        o gmake@4.1
+
+        """
+        spack.config.CONFIG.set("concretizer:duplicates:strategy", strategy)
+        s = Spec("py-shapely").concretized()
+        # Requirements on py-shapely
+        setuptools = s["py-shapely"].dependencies(name="py-setuptools", deptype="build")
+        assert len(setuptools) == 1 and setuptools[0].satisfies("@=60")
+
+        # Requirements on py-numpy
+        setuptools = s["py-numpy"].dependencies(name="py-setuptools", deptype="build")
+        assert len(setuptools) == 1 and setuptools[0].satisfies("@=59")
+        gmake = s["py-numpy"].dependencies(name="gmake", deptype="build")
+        assert len(gmake) == 1 and gmake[0].satisfies("@=4.1")
+
+        # Requirements on python
+        gmake = s["python"].dependencies(name="gmake", deptype="build")
+        assert len(gmake) == 1 and gmake[0].satisfies("@=3.0")
+
+    @pytest.mark.skipif(
+        os.environ.get("SPACK_TEST_SOLVER") == "original",
+        reason="Not supported by the original concretizer",
+    )
+    def test_solution_without_cycles(self):
+        """Tests that when we concretize a spec with cycles, a fallback kicks in to recompute
+        a solution without cycles.
+        """
+        s = Spec("cycle-a").concretized()
+        assert s["cycle-a"].satisfies("+cycle")
+        assert s["cycle-b"].satisfies("~cycle")
+
+        s = Spec("cycle-b").concretized()
+        assert s["cycle-a"].satisfies("~cycle")
+        assert s["cycle-b"].satisfies("+cycle")

lib/spack/spack/test/concretize_preferences.py

@@ -117,13 +117,9 @@ def test_preferred_compilers(self, compiler_str, spec_str):
         # etc.
         assert spec.compiler.satisfies(CompilerSpec(compiler_str))
 
+    @pytest.mark.only_clingo("Use case not supported by the original concretizer")
     def test_preferred_target(self, mutable_mock_repo):
         """Test preferred targets are applied correctly"""
-        # FIXME: This test was a false negative, since the default and
-        # FIXME: the preferred target were the same
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("Known bug in the original concretizer")
-
         spec = concretize("mpich")
         default = str(spec.target)
         preferred = str(spec.target.family)
@@ -151,9 +147,8 @@ def test_preferred_versions(self):
         spec = concretize("mpileaks")
         assert spec.version == Version("2.2")
 
+    @pytest.mark.only_clingo("This behavior is not enforced for the old concretizer")
     def test_preferred_versions_mixed_version_types(self):
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("This behavior is not enforced for the old concretizer")
         update_packages("mixedversions", "version", ["=2.0"])
         spec = concretize("mixedversions")
         assert spec.version == Version("2.0")
@@ -230,24 +225,20 @@ def test_preferred(self):
         spec.concretize()
         assert spec.version == Version("3.5.0")
 
+    @pytest.mark.only_clingo("This behavior is not enforced for the old concretizer")
     def test_preferred_undefined_raises(self):
         """Preference should not specify an undefined version"""
-        if spack.config.get("config:concretizer") == "original":
-            pytest.xfail("This behavior is not enforced for the old concretizer")
-
         update_packages("python", "version", ["3.5.0.1"])
         spec = Spec("python")
         with pytest.raises(spack.config.ConfigError):
             spec.concretize()
 
+    @pytest.mark.only_clingo("This behavior is not enforced for the old concretizer")
     def test_preferred_truncated(self):
         """Versions without "=" are treated as version ranges: if there is
         a satisfying version defined in the package.py, we should use that
         (don't define a new version).
         """
-        if spack.config.get("config:concretizer") == "original":
-            pytest.skip("This behavior is not enforced for the old concretizer")
-
         update_packages("python", "version", ["3.5"])
         spec = Spec("python")
         spec.concretize()

lib/spack/spack/test/concretize_requirements.py

@@ -3,7 +3,6 @@
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 import pathlib
-import sys
 
 import pytest
 
@@ -14,11 +13,14 @@
 import spack.repo
 import spack.util.spack_yaml as syaml
 import spack.version
-from spack.solver.asp import UnsatisfiableSpecError
+from spack.solver.asp import InternalConcretizerError, UnsatisfiableSpecError
 from spack.spec import Spec
 from spack.util.url import path_to_file_url
 
-pytestmark = pytest.mark.skipif(sys.platform == "win32", reason="Windows uses old concretizer")
+pytestmark = [
+    pytest.mark.not_on_windows("Windows uses old concretizer"),
+    pytest.mark.only_clingo("Original concretizer does not support configuration requirements"),
+]
 
 
 def update_packages_config(conf_str):
@@ -134,9 +136,6 @@ def fake_installs(monkeypatch, tmpdir):
 
 
 def test_one_package_multiple_reqs(concretize_scope, test_repo):
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     conf_str = """\
 packages:
   y:
@@ -153,9 +152,6 @@ def test_requirement_isnt_optional(concretize_scope, test_repo):
     """If a user spec requests something that directly conflicts
     with a requirement, make sure we get an error.
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     conf_str = """\
 packages:
   x:
@@ -173,9 +169,6 @@ def test_require_undefined_version(concretize_scope, test_repo):
     (it is assumed this is a typo, and raising the error here
     avoids a likely error when Spack attempts to fetch the version).
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     conf_str = """\
 packages:
   x:
@@ -192,9 +185,6 @@ def test_require_truncated(concretize_scope, test_repo):
     of the defined versions (vs. allowing the requirement to
     define a new version).
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     conf_str = """\
 packages:
   x:
@@ -256,9 +246,6 @@ def test_git_user_supplied_reference_satisfaction(
 def test_requirement_adds_new_version(
     concretize_scope, test_repo, mock_git_version_info, monkeypatch
 ):
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     repo_path, filename, commits = mock_git_version_info
     monkeypatch.setattr(
         spack.package_base.PackageBase, "git", path_to_file_url(repo_path), raising=False
@@ -289,9 +276,6 @@ def test_requirement_adds_version_satisfies(
     depends_on condition and make sure it is triggered (i.e. the
     dependency is added).
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration" " requirements")
-
     repo_path, filename, commits = mock_git_version_info
     monkeypatch.setattr(
         spack.package_base.PackageBase, "git", path_to_file_url(repo_path), raising=False
@@ -318,9 +302,6 @@ def test_requirement_adds_version_satisfies(
 def test_requirement_adds_git_hash_version(
     concretize_scope, test_repo, mock_git_version_info, monkeypatch
 ):
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     repo_path, filename, commits = mock_git_version_info
     monkeypatch.setattr(
         spack.package_base.PackageBase, "git", path_to_file_url(repo_path), raising=False
@@ -342,9 +323,6 @@ def test_requirement_adds_git_hash_version(
 def test_requirement_adds_multiple_new_versions(
     concretize_scope, test_repo, mock_git_version_info, monkeypatch
 ):
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     repo_path, filename, commits = mock_git_version_info
     monkeypatch.setattr(
         spack.package_base.PackageBase, "git", path_to_file_url(repo_path), raising=False
@@ -370,9 +348,6 @@ def test_preference_adds_new_version(
     """Normally a preference cannot define a new version, but that constraint
     is ignored if the version is a Git hash-based version.
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not enforce this constraint for preferences")
-
     repo_path, filename, commits = mock_git_version_info
     monkeypatch.setattr(
         spack.package_base.PackageBase, "git", path_to_file_url(repo_path), raising=False
@@ -398,9 +373,6 @@ def test_external_adds_new_version_that_is_preferred(concretize_scope, test_repo
     """Test that we can use a version, not declared in package recipe, as the
     preferred version if that version appears in an external spec.
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not enforce this constraint for preferences")
-
     conf_str = """\
 packages:
   y:
@@ -421,9 +393,6 @@ def test_requirement_is_successfully_applied(concretize_scope, test_repo):
     """If a simple requirement can be satisfied, make sure the
     concretization succeeds and the requirement spec is applied.
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     s1 = Spec("x").concretized()
     # Without any requirements/preferences, the later version is preferred
     assert s1.satisfies("@1.1")
@@ -443,9 +412,6 @@ def test_multiple_packages_requirements_are_respected(concretize_scope, test_rep
     """Apply requirements to two packages; make sure the concretization
     succeeds and both requirements are respected.
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     conf_str = """\
 packages:
   x:
@@ -463,9 +429,6 @@ def test_oneof(concretize_scope, test_repo):
     """'one_of' allows forcing the concretizer to satisfy one of
     the specs in the group (but not all have to be satisfied).
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     conf_str = """\
 packages:
   y:
@@ -483,9 +446,6 @@ def test_one_package_multiple_oneof_groups(concretize_scope, test_repo):
     """One package has two 'one_of' groups; check that both are
     applied.
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     conf_str = """\
 packages:
   y:
@@ -505,9 +465,6 @@ def test_one_package_multiple_oneof_groups(concretize_scope, test_repo):
 @pytest.mark.regression("34241")
 def test_require_cflags(concretize_scope, test_repo):
     """Ensures that flags can be required from configuration."""
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration" " requirements")
-
     conf_str = """\
 packages:
   y:
@@ -523,9 +480,6 @@ def test_requirements_for_package_that_is_not_needed(concretize_scope, test_repo
     a dependency of a concretized spec (in other words, none of
     the requirements are used for the requested spec).
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     # Note that the exact contents aren't important since this isn't
     # intended to be used, but the important thing is that a number of
     # packages have requirements applied
@@ -549,9 +503,6 @@ def test_oneof_ordering(concretize_scope, test_repo):
     This priority should override default priority (e.g. choosing
     later versions).
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     conf_str = """\
 packages:
   y:
@@ -568,9 +519,6 @@ def test_oneof_ordering(concretize_scope, test_repo):
 
 
 def test_reuse_oneof(concretize_scope, create_test_repo, mutable_database, fake_installs):
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     conf_str = """\
 packages:
   y:
@@ -591,9 +539,6 @@ def test_reuse_oneof(concretize_scope, create_test_repo, mutable_database, fake_
 
 def test_requirements_are_higher_priority_than_deprecation(concretize_scope, test_repo):
     """Test that users can override a deprecated version with a requirement."""
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     # @2.3 is a deprecated versions. Ensure that any_of picks both constraints,
     # since they are possible
     conf_str = """\
@@ -612,9 +557,6 @@ def test_requirements_are_higher_priority_than_deprecation(concretize_scope, tes
 @pytest.mark.parametrize("spec_str,requirement_str", [("x", "%gcc"), ("x", "%clang")])
 def test_default_requirements_with_all(spec_str, requirement_str, concretize_scope, test_repo):
     """Test that default requirements are applied to all packages."""
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     conf_str = """\
 packages:
   all:
@@ -640,8 +582,6 @@ def test_default_and_package_specific_requirements(
     concretize_scope, requirements, expectations, test_repo
 ):
     """Test that specific package requirements override default package requirements."""
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
     generic_req, specific_req = requirements
     generic_exp, specific_exp = expectations
     conf_str = """\
@@ -663,8 +603,6 @@ def test_default_and_package_specific_requirements(
 
 @pytest.mark.parametrize("mpi_requirement", ["mpich", "mpich2", "zmpi"])
 def test_requirements_on_virtual(mpi_requirement, concretize_scope, mock_packages):
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
     conf_str = """\
 packages:
   mpi:
@@ -686,8 +624,6 @@ def test_requirements_on_virtual(mpi_requirement, concretize_scope, mock_package
 def test_requirements_on_virtual_and_on_package(
     mpi_requirement, specific_requirement, concretize_scope, mock_packages
 ):
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
     conf_str = """\
 packages:
   mpi:
@@ -706,8 +642,6 @@ def test_requirements_on_virtual_and_on_package(
 
 
 def test_incompatible_virtual_requirements_raise(concretize_scope, mock_packages):
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
     conf_str = """\
     packages:
       mpi:
@@ -716,13 +650,12 @@ def test_incompatible_virtual_requirements_raise(concretize_scope, mock_packages
     update_packages_config(conf_str)
 
     spec = Spec("callpath ^zmpi")
-    with pytest.raises(UnsatisfiableSpecError):
+    # TODO (multiple nodes): recover a better error message later
+    with pytest.raises((UnsatisfiableSpecError, InternalConcretizerError)):
         spec.concretize()
 
 
 def test_non_existing_variants_under_all(concretize_scope, mock_packages):
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
     conf_str = """\
     packages:
       all:
@@ -805,9 +738,6 @@ def test_conditional_requirements_from_packages_yaml(
     """Test that conditional requirements are required when the condition is met,
     and optional when the condition is not met.
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     update_packages_config(packages_yaml)
     spec = Spec(spec_str).concretized()
     for match_str, expected in expected_satisfies:
@@ -883,9 +813,6 @@ def test_requirements_fail_with_custom_message(
     """Test that specs failing due to requirements not being satisfiable fail with a
     custom error message.
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     update_packages_config(packages_yaml)
     with pytest.raises(spack.error.SpackError, match=expected_message):
         Spec(spec_str).concretized()
@@ -899,9 +826,6 @@ def test_skip_requirement_when_default_requirement_condition_cannot_be_met(
     package. For those packages the requirement rule is not emitted, since it can be
     determined to be always false.
     """
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
-
     packages_yaml = """
         packages:
           all:
@@ -919,8 +843,6 @@ def test_skip_requirement_when_default_requirement_condition_cannot_be_met(
 
 
 def test_requires_directive(concretize_scope, mock_packages):
-    if spack.config.get("config:concretizer") == "original":
-        pytest.skip("Original concretizer does not support configuration requirements")
     compilers_yaml = pathlib.Path(concretize_scope) / "compilers.yaml"
     compilers_yaml.write_text(
         """
@@ -937,7 +859,7 @@ def test_requires_directive(concretize_scope, mock_packages):
     modules: []
 """
     )
-    spack.config.config.clear_caches()
+    spack.config.CONFIG.clear_caches()
 
     # This package requires either clang or gcc
     s = Spec("requires_clang_or_gcc").concretized()

lib/spack/spack/test/config.py

@@ -7,7 +7,6 @@
 import getpass
 import io
 import os
-import sys
 import tempfile
 from datetime import date
 
@@ -236,7 +235,7 @@ def test_write_key_to_disk(mock_low_high_config, compiler_specs):
     spack.config.set("compilers", b_comps["compilers"], scope="high")
 
     # Clear caches so we're forced to read from disk.
-    spack.config.config.clear_caches()
+    spack.config.CONFIG.clear_caches()
 
     # Same check again, to ensure consistency.
     check_compiler_config(a_comps["compilers"], *compiler_specs.a)
@@ -249,7 +248,7 @@ def test_write_to_same_priority_file(mock_low_high_config, compiler_specs):
     spack.config.set("compilers", b_comps["compilers"], scope="low")
 
     # Clear caches so we're forced to read from disk.
-    spack.config.config.clear_caches()
+    spack.config.CONFIG.clear_caches()
 
     # Same check again, to ensure consistency.
     check_compiler_config(a_comps["compilers"], *compiler_specs.a)
@@ -369,7 +368,7 @@ def test_substitute_config_variables(mock_low_high_config, monkeypatch):
     spack.config.set(
         "modules:default", {"roots": {"lmod": os.path.join("foo", "bar", "baz")}}, scope="low"
     )
-    spack.config.config.clear_caches()
+    spack.config.CONFIG.clear_caches()
     path = spack.config.get("modules:default:roots:lmod")
     assert spack_path.canonicalize_path(path) == os.path.normpath(
         os.path.join(mock_low_high_config.scopes["low"].path, os.path.join("foo", "bar", "baz"))
@@ -484,7 +483,7 @@ def test_parse_install_tree(config_settings, expected, mutable_config):
     assert projections == expected_proj
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="Padding unsupported on Windows")
+@pytest.mark.not_on_windows("Padding unsupported on Windows")
 @pytest.mark.parametrize(
     "config_settings,expected",
     [
@@ -816,7 +815,7 @@ def test_bad_config_section(mock_low_high_config):
         spack.config.get("foobar")
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="chmod not supported on Windows")
+@pytest.mark.not_on_windows("chmod not supported on Windows")
 @pytest.mark.skipif(getuid() == 0, reason="user is root")
 def test_bad_command_line_scopes(tmpdir, config):
     cfg = spack.config.Configuration()
@@ -854,18 +853,18 @@ def test_add_command_line_scopes(tmpdir, mutable_config):
 
 def test_nested_override():
     """Ensure proper scope naming of nested overrides."""
-    base_name = spack.config.overrides_base_name
+    base_name = spack.config._OVERRIDES_BASE_NAME
 
     def _check_scopes(num_expected, debug_values):
         scope_names = [
-            s.name for s in spack.config.config.scopes.values() if s.name.startswith(base_name)
+            s.name for s in spack.config.CONFIG.scopes.values() if s.name.startswith(base_name)
         ]
 
         for i in range(num_expected):
             name = "{0}{1}".format(base_name, i)
             assert name in scope_names
 
-            data = spack.config.config.get_config("config", name)
+            data = spack.config.CONFIG.get_config("config", name)
             assert data["debug"] == debug_values[i]
 
     # Check results from single and nested override
@@ -878,23 +877,23 @@ def _check_scopes(num_expected, debug_values):
 
 def test_alternate_override(monkeypatch):
     """Ensure proper scope naming of override when conflict present."""
-    base_name = spack.config.overrides_base_name
+    base_name = spack.config._OVERRIDES_BASE_NAME
 
     def _matching_scopes(regexpr):
         return [spack.config.InternalConfigScope("{0}1".format(base_name))]
 
     # Check that the alternate naming works
-    monkeypatch.setattr(spack.config.config, "matching_scopes", _matching_scopes)
+    monkeypatch.setattr(spack.config.CONFIG, "matching_scopes", _matching_scopes)
 
     with spack.config.override("config:debug", False):
         name = "{0}2".format(base_name)
 
         scope_names = [
-            s.name for s in spack.config.config.scopes.values() if s.name.startswith(base_name)
+            s.name for s in spack.config.CONFIG.scopes.values() if s.name.startswith(base_name)
         ]
         assert name in scope_names
 
-        data = spack.config.config.get_config("config", name)
+        data = spack.config.CONFIG.get_config("config", name)
         assert data["debug"] is False
 
 
@@ -1395,7 +1394,7 @@ def test_config_file_dir_failure(tmpdir, mutable_empty_config):
         spack.config.read_config_file(tmpdir.strpath)
 
 
-@pytest.mark.skipif(sys.platform == "win32", reason="chmod not supported on Windows")
+@pytest.mark.not_on_windows("chmod not supported on Windows")
 def test_config_file_read_perms_failure(tmpdir, mutable_empty_config):
     """Test reading a configuration file without permissions to ensure
     ConfigFileError is raised."""

lib/spack/spack/test/conftest.py

@@ -480,10 +480,10 @@ def __str__(self):
 
 @pytest.fixture(autouse=True)
 def mock_fetch_cache(monkeypatch):
-    """Substitutes spack.paths.fetch_cache with a mock object that does nothing
+    """Substitutes spack.paths.FETCH_CACHE with a mock object that does nothing
     and raises on fetch.
     """
-    monkeypatch.setattr(spack.caches, "fetch_cache", MockCache())
+    monkeypatch.setattr(spack.caches, "FETCH_CACHE", MockCache())
 
 
 @pytest.fixture()
@@ -716,7 +716,7 @@ def configuration_dir(tmpdir_factory, linux_os):
 
 def _create_mock_configuration_scopes(configuration_dir):
     """Create the configuration scopes used in `config` and `mutable_config`."""
-    scopes = [spack.config.InternalConfigScope("_builtin", spack.config.config_defaults)]
+    scopes = [spack.config.InternalConfigScope("_builtin", spack.config.CONFIG_DEFAULTS)]
     scopes += [
         spack.config.ConfigScope(name, str(configuration_dir.join(name)))
         for name in ["site", "system", "user"]
@@ -1935,7 +1935,25 @@ def shell_as(shell):
 @pytest.fixture()
 def nullify_globals(request, monkeypatch):
     ensure_configuration_fixture_run_before(request)
-    monkeypatch.setattr(spack.config, "config", None)
-    monkeypatch.setattr(spack.caches, "misc_cache", None)
+    monkeypatch.setattr(spack.config, "CONFIG", None)
+    monkeypatch.setattr(spack.caches, "MISC_CACHE", None)
+    monkeypatch.setattr(spack.caches, "FETCH_CACHE", None)
     monkeypatch.setattr(spack.repo, "PATH", None)
     monkeypatch.setattr(spack.store, "STORE", None)
+
+
+def pytest_runtest_setup(item):
+    # Skip tests if they are marked only clingo and are run with the original concretizer
+    only_clingo_marker = item.get_closest_marker(name="only_clingo")
+    if only_clingo_marker and os.environ.get("SPACK_TEST_SOLVER") == "original":
+        pytest.skip(*only_clingo_marker.args)
+
+    # Skip tests if they are marked only original and are run with clingo
+    only_original_marker = item.get_closest_marker(name="only_original")
+    if only_original_marker and os.environ.get("SPACK_TEST_SOLVER", "clingo") == "clingo":
+        pytest.skip(*only_original_marker.args)
+
+    # Skip test marked "not_on_windows" if they're run on Windows
+    not_on_windows_marker = item.get_closest_marker(name="not_on_windows")
+    if not_on_windows_marker and sys.platform == "win32":
+        pytest.skip(*not_on_windows_marker.args)