gh-143768: rebuild broken interpreter symlinks

[claydugo]

Summary

Fix venv so re-running it in a directory with stale interpreter symlinks
removes the broken links before recreating them, and add a regression test
to ensure existing environments get their interpreter refreshed without --clear.

Issue number

#143768

• Issue: venv fails with confusing ENOENT when existing venv has broken symlinks #143768

[aisk]

Hi, please avoid force push in the future, see the Dev Guide: https://devguide.python.org/getting-started/pull-request-lifecycle/#don-t-force-push

[claydugo]

Oops sorry about that!

[github-actions]

This PR is stale because it has been open for 30 days with no activity.

[gaborbernat]

The fix is correct and well-scoped: os.path.islink(dst) and not os.path.exists(dst) targets only dangling symlinks and completes venv's existing overwrite path without adding repair semantics. Background and the virtualenv comparison are in #143768.

The regression test covers symlinks=True only, but the failure in the original report is the --copies path, which raises a different exception (FileNotFoundError [Errno 2] during the copy) than the symlinks path. The fix already handles it, so the test should cover it too; otherwise the exact reported scenario has no regression coverage. See the inline suggestion.

[gaborbernat]

Add a symlinks=False (--copies) case so the path from the original report is covered:

builder=venv.EnvBuilder(with_pip=False, symlinks=False)
self.run_with_capture(builder.create, self.env_dir)
self.assertFalse(os.path.islink(python))
self.assertTrue(os.path.exists(python))

[claydugo]

Thanks for spotting this, I pushed coverage for the --copies path

[claydugo]

Hmm, I could use guidance on getting the change detection pipeline passing without force push. I might have gotten it in a bad state using the Github UI

[brettcannon]

Hmm, I could use guidance on getting the change detection pipeline passing without force push. I might have gotten it in a bad state using the Github UI

I don't know how to get is out of this wedged state. Mind closing this PR and opening a new one?

[claydugo]

Closing in favor of #150985