extensions.py: remove import of spack.cmd (#47963)

4 files changed, 30 insertions, 34 deletions

diff --git a/lib/spack/spack/cmd/__init__.py b/lib/spack/spack/cmd/__init__.py
index e0bcf6da8d..4b64a2529a 100644
--- a/lib/spack/spack/cmd/__init__.py
+++ b/lib/spack/spack/cmd/__init__.py
@@ -4,6 +4,7 @@
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
 
 import argparse
+import difflib
 import importlib
 import os
 import re
@@ -125,6 +126,8 @@ def get_module(cmd_name):
         tty.debug("Imported {0} from built-in commands".format(pname))
     except ImportError:
         module = spack.extensions.get_module(cmd_name)
+        if not module:
+            raise CommandNotFoundError(cmd_name)
 
     attr_setdefault(module, SETUP_PARSER, lambda *args: None)  # null-op
     attr_setdefault(module, DESCRIPTION, "")
@@ -691,3 +694,24 @@ def find_environment(args):
 def first_line(docstring):
     """Return the first line of the docstring."""
     return docstring.split("\n")[0]
+
+
+class CommandNotFoundError(spack.error.SpackError):
+    """Exception class thrown when a requested command is not recognized as
+    such.
+    """
+
+    def __init__(self, cmd_name):
+        msg = (
+            f"{cmd_name} is not a recognized Spack command or extension command; "
+            "check with `spack commands`."
+        )
+        long_msg = None
+
+        similar = difflib.get_close_matches(cmd_name, all_commands())
+
+        if 1 <= len(similar) <= 5:
+            long_msg = "\nDid you mean one of the following commands?\n  "
+            long_msg += "\n  ".join(similar)
+
+        super().__init__(msg, long_msg)
diff --git a/lib/spack/spack/extensions.py b/lib/spack/spack/extensions.py
index e13e3f17d4..af7766f098 100644
--- a/lib/spack/spack/extensions.py
+++ b/lib/spack/spack/extensions.py
@@ -5,7 +5,6 @@
 """Service functions and classes to implement the hooks
 for Spack's command extensions.
 """
-import difflib
 import glob
 import importlib
 import os
@@ -17,7 +16,6 @@ from typing import List
 
 import llnl.util.lang
 
-import spack.cmd
 import spack.config
 import spack.error
 import spack.util.path
@@ -25,9 +23,6 @@ import spack.util.path
 _extension_regexp = re.compile(r"spack-(\w[-\w]*)$")
 
 
-# TODO: For consistency we should use spack.cmd.python_name(), but
-#       currently this would create a circular relationship between
-#       spack.cmd and spack.extensions.
 def _python_name(cmd_name):
     return cmd_name.replace("-", "_")
 
@@ -211,8 +206,7 @@ def get_module(cmd_name):
         module = load_command_extension(cmd_name, folder)
         if module:
             return module
-    else:
-        raise CommandNotFoundError(cmd_name)
+    return None
 
 
 def get_template_dirs():
@@ -224,27 +218,6 @@ def get_template_dirs():
     return extensions
 
 
-class CommandNotFoundError(spack.error.SpackError):
-    """Exception class thrown when a requested command is not recognized as
-    such.
-    """
-
-    def __init__(self, cmd_name):
-        msg = (
-            "{0} is not a recognized Spack command or extension command;"
-            " check with `spack commands`.".format(cmd_name)
-        )
-        long_msg = None
-
-        similar = difflib.get_close_matches(cmd_name, spack.cmd.all_commands())
-
-        if 1 <= len(similar) <= 5:
-            long_msg = "\nDid you mean one of the following commands?\n  "
-            long_msg += "\n  ".join(similar)
-
-        super().__init__(msg, long_msg)
-
-
 class ExtensionNamingError(spack.error.SpackError):
     """Exception class thrown when a configured extension does not follow
     the expected naming convention.
diff --git a/lib/spack/spack/repo.py b/lib/spack/spack/repo.py
index c4a104c6b9..502aa4734b 100644
--- a/lib/spack/spack/repo.py
+++ b/lib/spack/spack/repo.py
@@ -41,6 +41,7 @@ import spack.patch
 import spack.provider_index
 import spack.spec
 import spack.tag
+import spack.tengine
 import spack.util.file_cache
 import spack.util.git
 import spack.util.naming as nm
@@ -1485,8 +1486,6 @@ class MockRepositoryBuilder:
                 Both "dep_type" and "condition" can default to ``None`` in which case
                 ``spack.dependency.default_deptype`` and ``spack.spec.Spec()`` are used.
         """
-        import spack.tengine  # avoid circular import
-
         dependencies = dependencies or []
         context = {"cls_name": nm.mod_to_class(name), "dependencies": dependencies}
         template = spack.tengine.make_environment().get_template("mock-repository/package.pyt")
diff --git a/lib/spack/spack/test/cmd_extensions.py b/lib/spack/spack/test/cmd_extensions.py
index 6a4fcc0fad..fe2ab2c70b 100644
--- a/lib/spack/spack/test/cmd_extensions.py
+++ b/lib/spack/spack/test/cmd_extensions.py
@@ -210,7 +210,7 @@ def test_missing_command():
     """Ensure that we raise the expected exception if the desired command is
     not present.
     """
-    with pytest.raises(spack.extensions.CommandNotFoundError):
+    with pytest.raises(spack.cmd.CommandNotFoundError):
         spack.cmd.get_module("no-such-command")
 
 
@@ -220,9 +220,9 @@ def test_missing_command():
         ("/my/bad/extension", spack.extensions.ExtensionNamingError),
         ("", spack.extensions.ExtensionNamingError),
         ("/my/bad/spack--extra-hyphen", spack.extensions.ExtensionNamingError),
-        ("/my/good/spack-extension", spack.extensions.CommandNotFoundError),
-        ("/my/still/good/spack-extension/", spack.extensions.CommandNotFoundError),
-        ("/my/spack-hyphenated-extension", spack.extensions.CommandNotFoundError),
+        ("/my/good/spack-extension", spack.cmd.CommandNotFoundError),
+        ("/my/still/good/spack-extension/", spack.cmd.CommandNotFoundError),
+        ("/my/spack-hyphenated-extension", spack.cmd.CommandNotFoundError),
     ],
     ids=["no_stem", "vacuous", "leading_hyphen", "basic_good", "trailing_slash", "hyphenated"],
 )