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fix(toolchains): exclude pycache symlinks from runtime files - #4233
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The runtime's `lib/**` glob matches the `__pycache__` symlinks added in bazel-contrib#3661, so they end up in runfiles. With `RULES_PYTHON_PYCACHE_DIR=/dev/null` they are symlinks to a character device, and packaging a binary into a tar layer fails (bazel-contrib#4198). The glob now excludes `__pycache__` and everything under it. The pyc cache is now keyed on the runtime archive's sha256 rather than a hash of the workspace root. The sources in an archive all share one mtime, so Python's mtime-and-size check can't tell a patch release's sources from the previous one's. The workspace hash didn't keep workspaces apart anyway: the repository contents cache shares one fetched runtime, symlinks included, across workspaces. The default root stops trying locations that are likely to be shared and instead tries a more reliably user-owned fallback: if `XDG_CACHE_HOME` is unset, then on non-Windows, `$HOME/.cache` is used (per [XDG][0]). On Windows, `%LOCALAPPDATA%` is used. (NB. [`platformdirs`][1] would choose `rules_python\Cache` rather than `rules_python_pycache`; the current change opts for one directory name everywhere.) [0]: https://specifications.freedesktop.org/basedir/latest/#variables [1]: https://platformdirs.readthedocs.io/en/latest/
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@rickeylev @aignas I have signed the CLA - let me know if you need the email address on this commit to match or something. |
rickeylev
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Oct 13, 2026
Key the pycache directory on a combined hash of the workspace root and runtime identifier so different workspaces and runtime archives do not collide, clarify comments in python_repository.bzl, and fix Sphinx MyST directive nesting and issue link formatting in docs and news.
rickeylev
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Oct 13, 2026
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The runtime's
lib/**glob matches the__pycache__symlinks added in #3661, so they end up in runfiles.With
RULES_PYTHON_PYCACHE_DIR=/dev/nullthey are symlinks to a character device, and packaging a binary into a tar layer fails (#4198). The glob now excludes__pycache__and everything under it.The pyc cache is now keyed on the runtime archive's sha256 rather than a hash of the workspace root. The sources in an archive all share one mtime, so Python's mtime-and-size check can't tell a patch release's sources from the previous one's. The workspace hash didn't keep workspaces apart anyway: the repository contents cache shares one fetched runtime, symlinks included, across workspaces.
The default root stops trying locations that are likely to be shared and instead tries a more reliably user-owned fallback: if
XDG_CACHE_HOMEis unset, then on non-Windows,$HOME/.cacheis used (per XDG). On Windows,%LOCALAPPDATA%is used. (NB.platformdirswould chooserules_python\Cacherather thanrules_python_pycache; the current change opts for one directory name everywhere.)Fixes #4198