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Starlarkify Python's build flags #3252
Description
As part of Starlarkification, we plan to move all Python-related build flags defined in Bazel core code into rules_python.
This:
- gives
rules_pythonowners more complete control over Bazel's Python support - reduces the need for bazel /
rules_pythonrelease synchronization - saves
rules_pythoncontributors from having to know how to patch Bazel. - saves Bazel devs from having to know the details of Python
This issue tracks the effort.
Also see:
- Starlarkify Python flags
- Starlarkify native Bazel flags (proposal)
- Starlarkify native Bazel flags (GitHub discussion)
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gregestren commentedon Sep 8, 2025
I'm happy to have this assigned to me!
Graveyard `--incompatible_use_python_toolchains`.
Graveyard no-op python2 related flags
build: remove no-op _native_rules_allowlist (#3275)
rickeylev commentedon Sep 17, 2025
FYI: I've added a CI job that uses bazel rolling. It won't shorten the iteration cycle, but you'll be able to more commit changes here with more confidence they work and won't regress. If they do, we'll see it in typical PRs. The CI job is non-blocking, so we can still merge, but it'll be much more visible.
Graveyard deprecated --python_top.
Remote outdated nn-toolchain resolution logic.
chore: remove non-toolchain runtime resolution logic. (#3280)
Graveyard deprecated --python_top.
refactor: read migrated native flags through a centralized accessor f…
Graveyard deprecated --python_top.
New incompatible flags disable ctx.fragments.py, ctx.fragments.bazel_py
Graveyard no-op python2-to-python3 migration flags
chore: reject py2 runtimes and remove usages of ctx.fragments.py.disa…
build: Starlarkify python flags (#3334)
Auto-set missing Python flag aliases for Bazel 9 with rules_python >=…
Inject `MODULE.bazel`-defined flag aliases as `--flag_alias=foo=//bar`.
Inject `MODULE.bazel`-defined flag aliases as `--flag_alias=foo=//bar`.
Enable `--incompatible_remove_ctx_bazel_py_fragment`, `--incompatible…
Delete BazelPythonConfiguration
Deleting PythonOptions and PythonConfiguration
shayanhoshyari commentedon Jan 8, 2026
@rickeylev @aignas Related to this, are the documentation now busted?
The docs say https://rules-python.readthedocs.io/en/stable/api/rules_python/python/config_settings/index.html#experimental_python_import_all_repositories
However, I tried setting it and nothing happened in
.1.8.0-rc1. Only setting the bazel's own--experimental_python_import_all_repositoriesworked. Looking at the code, seems thatread_possibly_native_flag(...)only reads therules_pythonvariant if--incompatible_remove_ctx_bazel_py_fragmentis set (which needs bazel > 9), but the doc does not mention this at all.gregestren commentedon Jan 8, 2026
FWIW I'd expect
--experimental_python_import_all_repositoriessyntax to work with any Bazel version. Bazel 9+ should automatically route to--//python/config_settings:experimental_python_import_all_repositories. Let us know if you see otherwise.Acknowledged the documentation is a separate concern.