Conftest.restore_import_state should restore sys.meta_path as well as sys.path #1140
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Now that restore_import_state restores meta_path, don't use monkeypatch to do that as well. That the ordering between the monkeypatch's and restore_import_state's teardown execution is indeterminate, so using both can cause problems.
Clean up the code a bit. Also, out of paranoia, also restore sys.path_hooks.
dairiki
force-pushed
the
fix.restore_import_state
branch
from
75ef6df
to
447058d
Compare
dairiki
force-pushed
the
fix.restore_import_state
branch
from
447058d
to
79629aa
Compare
dairiki
added a commit
to dairiki/lektor
that referenced
this pull request
Sep 11, 2023
… sys.path (lektor#1140) * test(conftest.restore_import_state): ensure sys.meta_path is restored * fix(conftest.restore_import_state): restore sys.meta_path * fix(test_pluginsystem): preserve sys.meta_path * refactor(conftest.restore_import_state): cleanup & paranoia * test(tests): check that tests do not alter sys.path * fix(tests): fix the tests that were munging sys.path
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
The
restore_import_statecontext manager (in conftest.py) is used to isolate tests with respect to any changes they may make insys.pathand any modules they may import.It turns out that
sys.meta_pathneeds to be restored as well. If that's not done, there are a couple of insidious bugs (spurious test failures) that crop up.Issue(s) Resolved
Spurious test failures.
Description of Changes
Restore
sys.meta_path.Some modules, when imported, add their own custom finders to sys.meta_path. If such a module is imported within a test that is protected by
restore_import_state, it is in effect, "unimported" at the end of the test. If another test also imports that module, it can add its finder to meta_path again.(This can result in a
RuntimeError: Plugin "webpack-support" is already registered, since, with a duplicate finder on meta_path, import.metadata.distributions() can list all distributions twice.)Demangle the finders on
sys.meta_pathIt gets worse.
It turns out that when
importlib_metadatais imported, it neuters the stdlib PathFinder (by deleting its find_distributions method). It then adds its own custom finder to handle distribution lookup instead.If
importlib_metadatais imported within a test that is protected byrestore_import_state, its custom finder gets removed from sys.meta_path at the end of the test. But the stdlib finder has been crippled at this point, so now attempts to list installed distributions fail.So here, we make a copy of the stdlib PathFinder before the test run and restore that at the end of the test.