[sean0407]

Summary

A persistent venv can retain a dangling package-directory symlink after the Python runtime changes. When initialization then creates a runtime file link beneath that path, os.makedirs(..., exist_ok=True) raises FileExistsError instead of recovering.

Remove the parent symlink only when it is confirmed dangling, then create the directory and the current runtime file link. Fixes #4269.

Checks

• Before: the issue reproduction raised FileExistsError at the parent-directory creation in a credential-isolated sandbox.
• After: cached_venv_replaces_dangling_package_symlink_test passed in the same isolated sandbox (1 test); it checks that the stale package link becomes a directory and the child link resolves to the current runfiles file.
• git diff --check passed.

The focused run was on macOS. Windows execution, Bazel, and buildifier were not run.

AI assistance: OpenAI Codex assisted with the patch and regression test; Sean is the submitting author.