"spack build-env" searches env for relevant spec (#21642)

If you install packages using spack install in an environment with
complex spec constraints, and the install fails, you may want to
test out the build using spack build-env; one issue (particularly
if you use concretize: together) is that it may be hard to pass
the appropriate spec that matches what the environment is
attempting to install.

This updates the build-env command to default to pulling a matching
spec from the environment rather than concretizing what the user
provides on the command line independently.

This makes a similar change to spack cd.

If the user-provided spec matches multiple specs in the environment,
then these commands will now report an error and display all
matching specs (to help the user specify).

Co-authored-by: Gregory Becker <becker33@llnl.gov>

lib/spack/spack/cmd/__init__.py

@@ -181,6 +181,19 @@ def parse_specs(args, **kwargs):
         raise spack.error.SpackError(msg)
 
 
+def matching_spec_from_env(spec):
+    """
+    Returns a concrete spec, matching what is available in the environment.
+    If no matching spec is found in the environment (or if no environment is
+    active), this will return the given spec but concretized.
+    """
+    env = spack.environment.get_env({}, cmd_name)
+    if env:
+        return env.matching_spec(spec) or spec.concretized()
+    else:
+        return spec.concretized()
+
+
 def elide_list(line_list, max_num=10):
     """Takes a long list and limits it to a smaller number of elements,
        replacing intervening elements with '...'.  For example::

lib/spack/spack/cmd/common/env_utility.py

@@ -53,11 +53,13 @@ def emulate_env_utility(cmd_name, context, args):
         spec = args.spec[0]
         cmd = args.spec[1:]
 
-    specs = spack.cmd.parse_specs(spec, concretize=True)
+    specs = spack.cmd.parse_specs(spec, concretize=False)
     if len(specs) > 1:
         tty.die("spack %s only takes one spec." % cmd_name)
     spec = specs[0]
 
+    spec = spack.cmd.matching_spec_from_env(spec)
+
     build_environment.setup_package(spec.package, args.dirty, context)
 
     if args.dump:

lib/spack/spack/cmd/location.py

@@ -98,9 +98,8 @@ def location(parser, args):
                 print(spack.repo.path.dirname_for_package_name(spec.name))
 
             else:
-                # These versions need concretized specs.
-                spec.concretize()
-                pkg = spack.repo.get(spec)
+                spec = spack.cmd.matching_spec_from_env(spec)
+                pkg = spec.package
 
                 if args.stage_dir:
                     print(pkg.stage.path)

lib/spack/spack/environment.py

@@ -1505,6 +1505,67 @@ def concretized_specs(self):
         for s, h in zip(self.concretized_user_specs, self.concretized_order):
             yield (s, self.specs_by_hash[h])
 
+    def matching_spec(self, spec):
+        """
+        Given a spec (likely not concretized), find a matching concretized
+        spec in the environment.
+
+        The matching spec does not have to be installed in the environment,
+        but must be concrete (specs added with `spack add` without an
+        intervening `spack concretize` will not be matched).
+
+        If there is a single root spec that matches the provided spec or a
+        single dependency spec that matches the provided spec, then the
+        concretized instance of that spec will be returned.
+
+        If multiple root specs match the provided spec, or no root specs match
+        and multiple dependency specs match, then this raises an error
+        and reports all matching specs.
+        """
+        # Root specs will be keyed by concrete spec, value abstract
+        # Dependency-only specs will have value None
+        matches = {}
+
+        for user_spec, concretized_user_spec in self.concretized_specs():
+            if concretized_user_spec.satisfies(spec):
+                matches[concretized_user_spec] = user_spec
+            for dep_spec in concretized_user_spec.traverse(root=False):
+                if dep_spec.satisfies(spec):
+                    # Don't overwrite the abstract spec if present
+                    # If not present already, set to None
+                    matches[dep_spec] = matches.get(dep_spec, None)
+
+        if not matches:
+            return None
+        elif len(matches) == 1:
+            return list(matches.keys())[0]
+
+        root_matches = dict((concrete, abstract)
+                            for concrete, abstract in matches.items()
+                            if abstract)
+
+        if len(root_matches) == 1:
+            return root_matches[0][1]
+
+        # More than one spec matched, and either multiple roots matched or
+        # none of the matches were roots
+        # If multiple root specs match, it is assumed that the abstract
+        # spec will most-succinctly summarize the difference between them
+        # (and the user can enter one of these to disambiguate)
+        match_strings = []
+        fmt_str = '{hash:7}  ' + spack.spec.default_format
+        for concrete, abstract in matches.items():
+            if abstract:
+                s = 'Root spec %s\n  %s' % (abstract, concrete.format(fmt_str))
+            else:
+                s = 'Dependency spec\n  %s' % concrete.format(fmt_str)
+            match_strings.append(s)
+        matches_str = '\n'.join(match_strings)
+
+        msg = ("{0} matches multiple specs in the environment {1}: \n"
+               "{2}".format(str(spec), self.name, matches_str))
+        raise SpackEnvironmentError(msg)
+
     def removed_specs(self):
         """Tuples of (user spec, concrete spec) for all specs that will be
            removed on nexg concretize."""

lib/spack/spack/test/cmd/common/arguments.py

@@ -12,6 +12,7 @@
 import spack.cmd
 import spack.cmd.common.arguments as arguments
 import spack.config
+import spack.environment as ev
 
 
 @pytest.fixture()
@@ -65,3 +66,40 @@ def test_parse_spec_flags_with_spaces(
 
     assert all(x not in s.variants for x in unexpected_variants)
     assert all(x in s.variants for x in expected_variants)
+
+
+@pytest.mark.usefixtures('config')
+def test_match_spec_env(mock_packages, mutable_mock_env_path):
+    """
+    Concretize a spec with non-default options in an environment. Make
+    sure that when we ask for a matching spec when the environment is
+    active that we get the instance concretized in the environment.
+    """
+    # Initial sanity check: we are planning on choosing a non-default
+    # value, so make sure that is in fact not the default.
+    check_defaults = spack.cmd.parse_specs(['a'], concretize=True)[0]
+    assert not check_defaults.satisfies('foobar=baz')
+
+    e = ev.create('test')
+    e.add('a foobar=baz')
+    e.concretize()
+    with e:
+        env_spec = spack.cmd.matching_spec_from_env(
+            spack.cmd.parse_specs(['a'])[0])
+        assert env_spec.satisfies('foobar=baz')
+        assert env_spec.concrete
+
+
+@pytest.mark.usefixtures('config')
+def test_multiple_env_match_raises_error(mock_packages, mutable_mock_env_path):
+    e = ev.create('test')
+    e.add('a foobar=baz')
+    e.add('a foobar=fee')
+    e.concretize()
+    with e:
+        with pytest.raises(
+                spack.environment.SpackEnvironmentError) as exc_info:
+
+            spack.cmd.matching_spec_from_env(spack.cmd.parse_specs(['a'])[0])
+
+    assert 'matches multiple specs' in exc_info.value.message