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fix: preserve bootstrap_impl in exec config - #4477
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StephanDollberg wants to merge 2 commits into
Open
StephanDollberg wants to merge 2 commits into
StephanDollberg wants to merge 2 commits into
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With Bazel 10, `--bootstrap_impl=script` no longer applies to Python executables built as tools, e.g. a `py_binary` run by a `genrule`. They fall back to `system_python` and fail to start on hosts without a `python3`. Give the flag universal scope, as 159b6c2 did for `python_version` and 05916c1 for `venvs_use_declare_symlink`.
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PR was created with AI help, I'll be responding to comments myself. |
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🟡 Changes recommended
The existing genrule tests do not cover command-line bootstrap flag propagation into the exec configuration, leaving a regression test with a plain py_binary tool under Bazel 10 needed.
1 open issue
What changed in this PR
Preserves --bootstrap_impl across Bazel 10 exec transitions so Python build tools honor the selected bootstrap instead of reverting to system_python.
Changes:
- Adds a
scopeattribute to rules_python’s string build-setting rule. - Gives
bootstrap_impluniversal scope so its value propagates to build tools. - Documents the behavior and adds a release note.
| File | Description |
|---|---|
python/private/flags.bzl |
Exposes the Bazel-recognized scope attribute. |
python/config_settings/BUILD.bazel |
Sets universal scope for bootstrap_impl. |
news/bootstrap-impl-exec-config.fixed.md |
Announces the Bazel 10 build-tool bootstrap fix. |
docs/api/rules_python/python/config_settings/index.md |
Documents flag propagation to exec configurations. |
Review effort: Balanced
| # configuration. Bazel 10 resets Starlark flags in exec configurations | ||
| # unless they have universal scope | ||
| # (https://github.com/bazelbuild/bazel/issues/26909). | ||
| scope = "universal", |
Author
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Will do if maintainers agree.
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Yes please, a test for this would be good.
Builds a py_binary genrule tool with --bootstrap_impl=script set on the command line and checks that it gets the script bootstrap.
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With Bazel 10,
--bootstrap_impl=scriptno longer applies to Pythonexecutables built as tools, e.g. a
py_binaryrun by agenrule. Theyfall back to
system_pythonand fail to start on hosts without apython3.Give the flag universal scope, as 159b6c2 did for
python_versionand05916c1 for
venvs_use_declare_symlink.