build: Starlarkify python flags (#3334)

Add starlark flags for `--python_path`, `--build_python_zip` and
`--incompatible_default_to_explicit_init_py`.

- The transitions logic is updated to set both the native and starlark
versions of the flags to allow alternating between them until the native
ones are removed.
- `--build_python_zip` is changed to `boolean` instead of `Tristate`
with default value set to `True` on `windows` and `False` otherwise.
- `scope = universal` attribute is added to the starlark flags so they
can be propagated to exec config on Bazel 9. This required upgrading
`bazel_skylib` version to have `scope` attribute defined.

Work towards: #3252

cc @gregestren

---------

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
Co-authored-by: Richard Levasseur <rlevasseur@google.com>

Author: 3 people

.bazelrc

@@ -16,6 +16,7 @@ test --test_output=errors
 # creating (possibly empty) __init__.py files and adding them to the srcs of
 # Python targets as required.
 build --incompatible_default_to_explicit_init_py
+build --//python/config_settings:incompatible_default_to_explicit_init_py=True
 
 # Ensure ongoing compatibility with this flag.
 common --incompatible_disallow_struct_provider_syntax

CHANGELOG.md

@@ -85,6 +85,8 @@ END_UNRELEASED_TEMPLATE
   evaluated, see [our docs](/pypi/download.html#customizing-requires-dist-resolution) on customizing `Requires-Dist` resolution.
 * (toolchains) Added Python versions 3.14.0, 3.13.8, 3.12.12, 3.11.14, 3.10.19, and 3.9.24
   from the [20251010] release.
+* (deps) (bzlmod) Upgraded to `bazel-skylib` version
+  [1.8.2](https://github.com/bazelbuild/bazel-skylib/releases/tag/1.8.2)
 
 [20251010]: https://github.com/astral-sh/python-build-standalone/releases/tag/20251010
 

MODULE.bazel

@@ -5,7 +5,7 @@ module(
 )
 
 bazel_dep(name = "bazel_features", version = "1.21.0")
-bazel_dep(name = "bazel_skylib", version = "1.8.1")
+bazel_dep(name = "bazel_skylib", version = "1.8.2")
 bazel_dep(name = "rules_cc", version = "0.1.5")
 bazel_dep(name = "platforms", version = "0.0.11")
 

docs/api/rules_python/python/config_settings/index.md

@@ -24,6 +24,65 @@ This is a transition flag and will be removed in a subsequent release.
 ::::
 :::
 
+::::{bzl:flag} build_python_zip
+Controls if a `py_binary/py_test` output is a self-executable zipapp.
+
+When enabled, the output of `py_binary` or `py_test` targets will be a
+self-executable zipapp.
+
+:::{note}
+This affects _all_ `py_binary` and `py_test` targets in the build, not
+only the target(s) specified on the command line.
+:::
+
+Values:
+* `true`
+* `false`
+
+This flag replaces the Bazel builtin `--build_python_zip` flag.
+
+:::{versionadded} VERSION_NEXT_FEATURE
+:::
+::::
+
+::::{bzl:flag} experimental_python_import_all_repositories
+Controls whether repository directories are added to the import path.
+
+When enabled, the top-level directories in the runfiles root directory (which
+are presumbed to be repository directories) are added to the Python import
+search path.
+
+It's recommended to set this to **`false`** to avoid external dependencies
+unexpectedly interferring with import searching.
+
+Values;
+* `true` (default)
+* `false`
+
+This flag replaces the Bazel builtin
+`--experimental_python_import_all_repositories` flag.
+
+:::{versionadded} VERSION_NEXT_FEATURE
+:::
+::::
+
+::::{bzl:flag} python_path
+A fallback path to use for Python for particular legacy Windows-specific code paths.
+
+Deprecated, do not use. This flag is largely a no-op and was replaced by
+toolchains. It only remains for some legacy Windows code-paths that will
+be removed.
+
+This flag replaces the Bazel builtin `--python_path` flag.
+
+:::{deprecated} VERSION_NEXT_FEATURE
+Use toolchains instead.
+:::
+
+:::{versionadded} VERSION_NEXT_FEATURE
+:::
+::::
+
 :::{bzl:flag} python_version
 Determines the default hermetic Python toolchain version. This can be set to
 one of the values that `rules_python` maintains.
@@ -33,6 +92,29 @@ one of the values that `rules_python` maintains.
 Parses the value of the `python_version` and transforms it into a `X.Y` value.
 :::
 
+::::{bzl:flag} incompatible_default_to_explicit_init_py
+Controls if missing `__init__.py` files are generated or not.
+
+If false, `py_binary` and `py_test` will, for every `*.py` and `*.so` file,
+create `__init__.py` files for the containing directory, and all parent
+directories, that do not already have an `__init__.py` file. If true, this
+behavior is disabled.
+
+It's recommended to disable this behavior to avoid surprising import effects
+from directories being importable when they otherwise wouldn't be, and for
+how it can interfere with implicit namespace packages.
+
+Values:
+* `true`: do not generate missing `__init__.py` files
+* `false` (default): generate missing `__init__.py` files
+
+This flag replaces the Bazel builtin
+`--incompatible_default_to_explicit_init_py` flag.
+
+:::{versionadded} VERSION_NEXT_FEATURE
+:::
+::::
+
 :::{bzl:target} is_python_*
 config_settings to match Python versions
 

examples/build_file_generation/WORKSPACE

@@ -7,54 +7,7 @@ workspace(name = "build_file_generation_example")
 # file.  When the symbol is loaded you can use the rule.
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
-######################################################################
-# We need rules_go and bazel_gazelle, to build the gazelle plugin from source.
-# Setup instructions for this section are at
-# https://github.com/bazelbuild/bazel-gazelle#running-gazelle-with-bazel
-# You may need to update the version of the rule, which is listed in the above
-# documentation.
-######################################################################
-
-# Define an http_archive rule that will download the below ruleset,
-# test the sha, and extract the ruleset to you local bazel cache.
-
-http_archive(
-    name = "io_bazel_rules_go",
-    sha256 = "9d72f7b8904128afb98d46bbef82ad7223ec9ff3718d419afb355fddd9f9484a",
-    urls = [
-        "https://mirror.bazel.build/github.com/bazel-contrib/rules_go/releases/download/v0.55.1/rules_go-v0.55.1.zip",
-        "https://github.com/bazel-contrib/rules_go/releases/download/v0.55.1/rules_go-v0.55.1.zip",
-    ],
-)
-
-# Download the bazel_gazelle ruleset.
-http_archive(
-    name = "bazel_gazelle",
-    sha256 = "75df288c4b31c81eb50f51e2e14f4763cb7548daae126817247064637fd9ea62",
-    urls = [
-        "https://mirror.bazel.build/github.com/bazelbuild/bazel-gazelle/releases/download/v0.36.0/bazel-gazelle-v0.36.0.tar.gz",
-        "https://github.com/bazelbuild/bazel-gazelle/releases/download/v0.36.0/bazel-gazelle-v0.36.0.tar.gz",
-    ],
-)
-
-# Load rules_go ruleset and expose the toolchain and dep rules.
-load("@bazel_gazelle//:deps.bzl", "gazelle_dependencies")
-load("@io_bazel_rules_go//go:deps.bzl", "go_register_toolchains", "go_rules_dependencies")
-
-# go_rules_dependencies is a function that registers external dependencies
-# needed by the Go rules.
-# See: https://github.com/bazelbuild/rules_go/blob/master/go/dependencies.rst#go_rules_dependencies
-go_rules_dependencies()
-
-# go_rules_dependencies is a function that registers external dependencies
-# needed by the Go rules.
-# See: https://github.com/bazelbuild/rules_go/blob/master/go/dependencies.rst#go_rules_dependencies
-go_register_toolchains(version = "1.21.13")
-
-# The following call configured the gazelle dependencies, Go environment and Go SDK.
-gazelle_dependencies()
-
-# Remaining setup is for rules_python.
+# Setup rules_python.
 
 # DON'T COPY_PASTE THIS.
 # Our example uses `local_repository` to point to the HEAD version of rules_python.
@@ -124,6 +77,53 @@ load("@pip//:requirements.bzl", "install_deps")
 # Initialize repositories for all packages in requirements_lock.txt.
 install_deps()
 
+######################################################################
+# We need rules_go and bazel_gazelle, to build the gazelle plugin from source.
+# Setup instructions for this section are at
+# https://github.com/bazelbuild/bazel-gazelle#running-gazelle-with-bazel
+# You may need to update the version of the rule, which is listed in the above
+# documentation.
+######################################################################
+
+# Define an http_archive rule that will download the below ruleset,
+# test the sha, and extract the ruleset to you local bazel cache.
+
+http_archive(
+    name = "io_bazel_rules_go",
+    sha256 = "9d72f7b8904128afb98d46bbef82ad7223ec9ff3718d419afb355fddd9f9484a",
+    urls = [
+        "https://mirror.bazel.build/github.com/bazel-contrib/rules_go/releases/download/v0.55.1/rules_go-v0.55.1.zip",
+        "https://github.com/bazel-contrib/rules_go/releases/download/v0.55.1/rules_go-v0.55.1.zip",
+    ],
+)
+
+# Download the bazel_gazelle ruleset.
+http_archive(
+    name = "bazel_gazelle",
+    sha256 = "75df288c4b31c81eb50f51e2e14f4763cb7548daae126817247064637fd9ea62",
+    urls = [
+        "https://mirror.bazel.build/github.com/bazelbuild/bazel-gazelle/releases/download/v0.36.0/bazel-gazelle-v0.36.0.tar.gz",
+        "https://github.com/bazelbuild/bazel-gazelle/releases/download/v0.36.0/bazel-gazelle-v0.36.0.tar.gz",
+    ],
+)
+
+# Load rules_go ruleset and expose the toolchain and dep rules.
+load("@bazel_gazelle//:deps.bzl", "gazelle_dependencies")
+load("@io_bazel_rules_go//go:deps.bzl", "go_register_toolchains", "go_rules_dependencies")
+
+# go_rules_dependencies is a function that registers external dependencies
+# needed by the Go rules.
+# See: https://github.com/bazelbuild/rules_go/blob/master/go/dependencies.rst#go_rules_dependencies
+go_rules_dependencies()
+
+# go_rules_dependencies is a function that registers external dependencies
+# needed by the Go rules.
+# See: https://github.com/bazelbuild/rules_go/blob/master/go/dependencies.rst#go_rules_dependencies
+go_register_toolchains(version = "1.21.13")
+
+# The following call configured the gazelle dependencies, Go environment and Go SDK.
+gazelle_dependencies()
+
 # The rules_python gazelle extension has some third-party go dependencies
 # which we need to fetch in order to compile it.
 load("@rules_python_gazelle_plugin//:deps.bzl", _py_gazelle_deps = "gazelle_deps")

gazelle/.bazelrc

@@ -7,6 +7,7 @@ test --test_output=errors
 # creating (possibly empty) __init__.py files and adding them to the srcs of
 # Python targets as required.
 build --incompatible_default_to_explicit_init_py
+build --@rules_python//python/config_settings:incompatible_default_to_explicit_init_py=True
 
 # Windows makes use of runfiles for some rules
 build --enable_runfiles

gazelle/MODULE.bazel

@@ -4,7 +4,7 @@ module(
     compatibility_level = 1,
 )
 
-bazel_dep(name = "bazel_skylib", version = "1.6.1")
+bazel_dep(name = "bazel_skylib", version = "1.8.2")
 bazel_dep(name = "rules_python", version = "0.18.0")
 bazel_dep(name = "rules_go", version = "0.55.1", repo_name = "io_bazel_rules_go")
 bazel_dep(name = "gazelle", version = "0.36.0", repo_name = "bazel_gazelle")

gazelle/WORKSPACE

@@ -2,6 +2,19 @@ workspace(name = "rules_python_gazelle_plugin")
 
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
+http_archive(
+    name = "bazel_skylib",
+    sha256 = "6e78f0e57de26801f6f564fa7c4a48dc8b36873e416257a92bbb0937eeac8446",
+    urls = [
+        "https://mirror.bazel.build/github.com/bazelbuild/bazel-skylib/releases/download/1.8.2/bazel-skylib-1.8.2.tar.gz",
+        "https://github.com/bazelbuild/bazel-skylib/releases/download/1.8.2/bazel-skylib-1.8.2.tar.gz",
+    ],
+)
+
+load("@bazel_skylib//:workspace.bzl", "bazel_skylib_workspace")
+
+bazel_skylib_workspace()
+
 http_archive(
     name = "io_bazel_rules_go",
     sha256 = "9d72f7b8904128afb98d46bbef82ad7223ec9ff3718d419afb355fddd9f9484a",

internal_dev_deps.bzl

@@ -60,10 +60,10 @@ def rules_python_internal_deps():
 
     http_archive(
         name = "bazel_skylib",
-        sha256 = "bc283cdfcd526a52c3201279cda4bc298652efa898b10b4db0837dc51652756f",
+        sha256 = "6e78f0e57de26801f6f564fa7c4a48dc8b36873e416257a92bbb0937eeac8446",
         urls = [
-            "https://mirror.bazel.build/github.com/bazelbuild/bazel-skylib/releases/download/1.7.1/bazel-skylib-1.7.1.tar.gz",
-            "https://github.com/bazelbuild/bazel-skylib/releases/download/1.7.1/bazel-skylib-1.7.1.tar.gz",
+            "https://mirror.bazel.build/github.com/bazelbuild/bazel-skylib/releases/download/1.8.2/bazel-skylib-1.8.2.tar.gz",
+            "https://github.com/bazelbuild/bazel-skylib/releases/download/1.8.2/bazel-skylib-1.8.2.tar.gz",
         ],
     )
 

python/config_settings/BUILD.bazel

@@ -1,5 +1,6 @@
 load("@bazel_skylib//rules:common_settings.bzl", "bool_flag", "string_flag")
 load("@pythons_hub//:versions.bzl", "DEFAULT_PYTHON_VERSION", "MINOR_MAPPING", "PYTHON_VERSIONS")
+load("@rules_python_internal//:rules_python_config.bzl", "config")
 load(
     "//python/private:flags.bzl",
     "AddSrcsToRunfilesFlag",
@@ -244,5 +245,28 @@ label_flag(
 bool_flag(
     name = "experimental_python_import_all_repositories",
     build_setting_default = True,
+    scope = "universal",
+    visibility = ["//visibility:public"],
+)
+
+bool_flag(
+    name = "build_python_zip",
+    build_setting_default = config.build_python_zip_default,
+    help = "Build python executable zip. Defaults to on on Windows, off on other platforms",
+    scope = "universal",
+    visibility = ["//visibility:public"],
+)
+
+bool_flag(
+    name = "incompatible_default_to_explicit_init_py",
+    build_setting_default = False,
+    scope = "universal",
+    visibility = ["//visibility:public"],
+)
+
+string_flag(
+    name = "python_path",
+    build_setting_default = "python",
+    scope = "universal",
     visibility = ["//visibility:public"],
 )