bugfix: config edit should work with a malformed spack.yaml

If you don't format `spack.yaml` correctly, `spack config edit` still fails and
you have to edit your `spack.yaml` manually.

- [x] Add some code to `_main()` to defer `ConfigFormatError` when loading the
  environment, until we know what command is being run.

- [x] Make `spack config edit` use `SPACK_ENV` instead of the config scope
  object to find `spack.yaml`, so it can work even if the environment is bad.

Co-authored-by: scheibelp <scheibel1@llnl.gov>

lib/spack/spack/cmd/config.py

@@ -170,12 +170,19 @@ def config_edit(args):
     With no arguments and an active environment, edit the spack.yaml for
     the active environment.
     """
-    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.')
+    spack_env = os.environ.get(ev.spack_env_var)
+    if spack_env and not args.scope:
+        # Don't use the scope object for envs, as `config edit` can be called
+        # for a malformed environment. Use SPACK_ENV to find spack.yaml.
+        config_file = ev.manifest_file(spack_env)
+    else:
+        # If we aren't editing a spack.yaml file, get config path from scope.
+        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)
     else:

lib/spack/spack/main.py

@@ -740,7 +740,7 @@ def _main(argv=None):
 
     Args:
         argv (list or None): command line arguments, NOT including
-            the executable name. If None, parses from sys.argv.
+            the executable name. If None, parses from ``sys.argv``.
 
     """
     # ------------------------------------------------------------------------
@@ -803,10 +803,17 @@ def _main(argv=None):
         spack.config.command_line_scopes = args.config_scopes
 
     # activate an environment if one was specified on the command line
+    env_format_error = None
     if not args.no_env:
-        env = spack.cmd.find_environment(args)
-        if env:
-            ev.activate(env, args.use_env_repo)
+        try:
+            env = spack.cmd.find_environment(args)
+            if env:
+                ev.activate(env, args.use_env_repo)
+        except spack.config.ConfigFormatError as e:
+            # print the context but delay this exception so that commands like
+            # `spack config edit` can still work with a bad environment.
+            e.print_context()
+            env_format_error = e
 
     # ------------------------------------------------------------------------
     # Things that require configuration should go below here
@@ -830,6 +837,13 @@ def _main(argv=None):
     # Re-parse with the proper sub-parser added.
     args, unknown = parser.parse_known_args()
 
+    # Now that we know what command this is and what its args are, determine
+    # whether we can continue with a bad environment and raise if not.
+    if env_format_error:
+        subcommand = getattr(args, "config_command", None)
+        if (cmd_name, subcommand) != ("config", "edit"):
+            raise env_format_error
+
     # many operations will fail without a working directory.
     set_working_dir()
 
@@ -854,7 +868,7 @@ def main(argv=None):
     The logic is all in ``_main()``.
 
     Args:
-        argv (list of str or None): command line arguments, NOT including
+        argv (list or None): command line arguments, NOT including
             the executable name. If None, parses from sys.argv.
 
     """