fix(bzlmod): set the default_version to the python_version flag

CHANGELOG.md

@@ -28,7 +28,11 @@ A brief description of the categories of changes:
 * Nothing yet
 
 ### Fixed
-* Nothing yet
+* (bzlmod) The `python.override(minor_mapping)` now merges the default and the
+  overridden versions ensuring that the resultant `minor_mapping` will always
+  have all of the python versions.
+* (bzlmod) The default value for the {obj}`--python_version` flag will now be
+  always set to the default python toolchain version value.
 
 ### Added
 * Nothing yet

examples/bzlmod/MODULE.bazel

@@ -42,17 +42,16 @@ python.toolchain(
 python.override(
     available_python_versions = [
         "3.10.9",
+        "3.9.18",
         "3.9.19",
         # The following is used by the `other_module` and we need to include it here
         # as well.
         "3.11.8",
     ],
     # Also override the `minor_mapping` so that the root module,
-    # instead of rules_python's defaults, controls what full version
-    # is used when `3.x` is requested.
+    # instead of rules_python's defaulting to the latest available version,
+    # controls what full version is used when `3.x` is requested.
     minor_mapping = {
-        "3.10": "3.10.9",
-        "3.11": "3.11.8",
         "3.9": "3.9.19",
     },
 )
@@ -90,7 +89,7 @@ python.single_version_platform_override(
 # See the tests folder for various examples on using multiple Python versions.
 # The names "python_3_9" and "python_3_10" are autmatically created by the repo
 # rules based on the `python_version` arg values.
-use_repo(python, "python_3_10", "python_3_9", "python_versions")
+use_repo(python, "python_3_10", "python_3_9", "python_versions", "pythons_hub")
 
 # EXPERIMENTAL: This is experimental and may be removed without notice
 uv = use_extension("@rules_python//python/uv:extensions.bzl", "uv")

examples/bzlmod/tests/BUILD.bazel

@@ -1,8 +1,8 @@
 load("@python_versions//3.10:defs.bzl", py_binary_3_10 = "py_binary", py_test_3_10 = "py_test")
 load("@python_versions//3.11:defs.bzl", py_binary_3_11 = "py_binary", py_test_3_11 = "py_test")
 load("@python_versions//3.9:defs.bzl", py_binary_3_9 = "py_binary", py_test_3_9 = "py_test")
+load("@pythons_hub//:interpreters.bzl", "MINOR_MAPPING")
 load("@rules_python//python:defs.bzl", "py_binary", "py_test")
-load("@rules_python//python:versions.bzl", "MINOR_MAPPING")
 load("@rules_python//python/config_settings:transition.bzl", py_versioned_binary = "py_binary", py_versioned_test = "py_test")
 
 py_binary(

internal_setup.bzl

@@ -22,13 +22,25 @@ load("@rules_bazel_integration_test//bazel_integration_test:deps.bzl", "bazel_in
 load("@rules_bazel_integration_test//bazel_integration_test:repo_defs.bzl", "bazel_binaries")
 load("@rules_proto//proto:repositories.bzl", "rules_proto_dependencies", "rules_proto_toolchains")
 load("//:version.bzl", "SUPPORTED_BAZEL_VERSIONS")
+load("//python/private:bzlmod_enabled.bzl", "BZLMOD_ENABLED")  # buildifier: disable=bzl-visibility
 load("//python/private:internal_config_repo.bzl", "internal_config_repo")  # buildifier: disable=bzl-visibility
+load("//python/private:pythons_hub.bzl", "hub_repo")  # buildifier: disable=bzl-visibility
 load("//python/private/pypi:deps.bzl", "pypi_deps")  # buildifier: disable=bzl-visibility
 
 def rules_python_internal_setup():
     """Setup for rules_python tests and tools."""
 
     internal_config_repo(name = "rules_python_internal")
+    if not BZLMOD_ENABLED:
+        hub_repo(
+            name = "pythons_hub",
+            minor_mapping = {},
+            default_python_version = "",
+            toolchain_prefixes = [],
+            toolchain_python_versions = [],
+            toolchain_set_python_version_constraints = [],
+            toolchain_user_repository_names = [],
+        )
 
     # Because we don't use the pip_install rule, we have to call this to fetch its deps
     pypi_deps()

python/config_settings/BUILD.bazel

@@ -1,5 +1,7 @@
 load("@bazel_skylib//rules:common_settings.bzl", "string_flag")
-load("//python:versions.bzl", "MINOR_MAPPING", "TOOL_VERSIONS")
+load("@pythons_hub//:interpreters.bzl", "DEFAULT_PYTHON_VERSION", "MINOR_MAPPING", "PYTHON_VERSIONS")
+load("//python:versions.bzl", "TOOL_VERSIONS", _DEFAULT_MINOR_MAPPING = "MINOR_MAPPING")
+load("//python/private:bzlmod_enabled.bzl", "BZLMOD_ENABLED")
 load(
     "//python/private:flags.bzl",
     "BootstrapImplFlag",
@@ -28,8 +30,9 @@ filegroup(
 
 construct_config_settings(
     name = "construct_config_settings",
-    minor_mapping = MINOR_MAPPING,
-    versions = TOOL_VERSIONS.keys(),
+    default_version = DEFAULT_PYTHON_VERSION,
+    minor_mapping = MINOR_MAPPING if BZLMOD_ENABLED else _DEFAULT_MINOR_MAPPING,
+    versions = PYTHON_VERSIONS if BZLMOD_ENABLED else sorted(TOOL_VERSIONS.keys()),
 )
 
 string_flag(

python/private/BUILD.bazel

@@ -157,6 +157,7 @@ bzl_library(
     deps = [
         ":bazel_tools_bzl",
         ":internal_config_repo_bzl",
+        ":pythons_hub_bzl",
         "//python/private/pypi:deps_bzl",
     ],
 )
@@ -204,6 +205,7 @@ bzl_library(
     srcs = ["pythons_hub.bzl"],
     deps = [
         ":py_toolchain_suite_bzl",
+        ":text_util_bzl",
     ],
 )
 

python/private/config_settings.bzl

@@ -22,25 +22,22 @@ load(":semver.bzl", "semver")
 _PYTHON_VERSION_FLAG = Label("//python/config_settings:python_version")
 _PYTHON_VERSION_MAJOR_MINOR_FLAG = Label("//python/config_settings:_python_version_major_minor")
 
-def construct_config_settings(*, name, versions, minor_mapping):  # buildifier: disable=function-docstring
+def construct_config_settings(*, name, default_version, versions, minor_mapping):  # buildifier: disable=function-docstring
     """Create a 'python_version' config flag and construct all config settings used in rules_python.
 
     This mainly includes the targets that are used in the toolchain and pip hub
     repositories that only match on the 'python_version' flag values.
 
     Args:
         name: {type}`str` A dummy name value that is no-op for now.
+        default_version: {type}`str` the default value for the `python_version` flag.
         versions: {type}`list[str]` A list of versions to build constraint settings for.
         minor_mapping: {type}`dict[str, str]` A mapping from `X.Y` to `X.Y.Z` python versions.
     """
     _ = name  # @unused
     _python_version_flag(
         name = _PYTHON_VERSION_FLAG.name,
-        # TODO: The default here should somehow match the MODULE config. Until
-        # then, use the empty string to indicate an unknown version. This
-        # also prevents version-unaware targets from inadvertently matching
-        # a select condition when they shouldn't.
-        build_setting_default = "",
+        build_setting_default = default_version,
         visibility = ["//visibility:public"],
     )
 

python/private/py_repositories.bzl

@@ -18,6 +18,7 @@ load("@bazel_tools//tools/build_defs/repo:http.bzl", _http_archive = "http_archi
 load("@bazel_tools//tools/build_defs/repo:utils.bzl", "maybe")
 load("//python/private/pypi:deps.bzl", "pypi_deps")
 load(":internal_config_repo.bzl", "internal_config_repo")
+load(":pythons_hub.bzl", "hub_repo")
 
 def http_archive(**kwargs):
     maybe(_http_archive, **kwargs)
@@ -32,6 +33,16 @@ def py_repositories():
         internal_config_repo,
         name = "rules_python_internal",
     )
+    maybe(
+        hub_repo,
+        name = "pythons_hub",
+        minor_mapping = {},
+        default_python_version = "",
+        toolchain_prefixes = [],
+        toolchain_python_versions = [],
+        toolchain_set_python_version_constraints = [],
+        toolchain_user_repository_names = [],
+    )
     http_archive(
         name = "bazel_skylib",
         sha256 = "74d544d96f4a5bb630d465ca8bbcfe231e3594e5aae57e1edbf17a6eb3ca2506",

python/private/pypi/config_settings.bzl

@@ -109,9 +109,14 @@ def config_settings(
 
     for python_version in [""] + python_versions:
         is_python = "is_python_{}".format(python_version or "version_unset")
-        native.alias(
+
+        # Do not rely on aliases in the `rules_python` so that we can just blindly
+        # add all of the found wheels on the internet to the select statement.
+        native.config_setting(
             name = is_python,
-            actual = Label("//python/config_settings:" + is_python),
+            flag_values = {
+                Label("//python/config_settings:_python_version_major_minor"): python_version,
+            },
             visibility = visibility,
         )
 

python/private/pypi/extension.bzl

@@ -15,7 +15,7 @@
 "pip module extension for use with bzlmod"
 
 load("@bazel_features//:features.bzl", "bazel_features")
-load("@pythons_hub//:interpreters.bzl", "DEFAULT_PYTHON_VERSION", "INTERPRETER_LABELS")
+load("@pythons_hub//:interpreters.bzl", "INTERPRETER_LABELS")
 load("//python/private:auth.bzl", "AUTH_ATTRS")
 load("//python/private:normalize_name.bzl", "normalize_name")
 load("//python/private:repo_utils.bzl", "repo_utils")
@@ -500,7 +500,6 @@ def _pip_impl(module_ctx):
                 key: json.encode(value)
                 for key, value in whl_map.items()
             },
-            default_version = _major_minor_version(DEFAULT_PYTHON_VERSION),
             packages = sorted(exposed_packages.get(hub_name, {})),
             groups = hub_group_map.get(hub_name),
         )

python/private/pypi/hub_repository.bzl

@@ -35,8 +35,6 @@ def _impl(rctx):
             key: [whl_alias(**v) for v in json.decode(values)]
             for key, values in rctx.attr.whl_map.items()
         },
-        default_version = rctx.attr.default_version,
-        default_config_setting = "//_config:is_python_" + rctx.attr.default_version,
         requirement_cycles = rctx.attr.groups,
     )
     for path, contents in aliases.items():
@@ -67,13 +65,6 @@ def _impl(rctx):
 
 hub_repository = repository_rule(
     attrs = {
-        "default_version": attr.string(
-            mandatory = True,
-            doc = """\
-This is the default python version in the format of X.Y. This should match
-what is setup by the 'python' extension using the 'is_default = True'
-setting.""",
-        ),
         "groups": attr.string_list_dict(
             mandatory = False,
         ),

python/private/pypi/render_pkg_aliases.bzl

@@ -198,7 +198,9 @@ def render_pkg_aliases(*, aliases, default_config_setting = None, requirement_cy
     Args:
         aliases: dict, the keys are normalized distribution names and values are the
             whl_alias instances.
-        default_config_setting: the default to be used for the aliases.
+        default_config_setting: the default to be used for the aliases. Effectively
+            only used in WORKSPACE because we are not setting the value of the
+            {obj}`--python_version` by default there.
         requirement_cycles: any package groups to also add.
 
     Returns:
@@ -278,13 +280,12 @@ def whl_alias(*, repo, version = None, config_setting = None, filename = None, t
         target_platforms = target_platforms,
     )
 
-def render_multiplatform_pkg_aliases(*, aliases, default_version = None, **kwargs):
+def render_multiplatform_pkg_aliases(*, aliases, **kwargs):
     """Render the multi-platform pkg aliases.
 
     Args:
         aliases: dict[str, list(whl_alias)] A list of aliases that will be
           transformed from ones having `filename` to ones having `config_setting`.
-        default_version: str, the default python version. Defaults to None.
         **kwargs: extra arguments passed to render_pkg_aliases.
 
     Returns:
@@ -302,7 +303,6 @@ def render_multiplatform_pkg_aliases(*, aliases, default_version = None, **kwarg
     config_setting_aliases = {
         pkg: multiplatform_whl_aliases(
             aliases = pkg_aliases,
-            default_version = default_version,
             glibc_versions = flag_versions.get("glibc_versions", []),
             muslc_versions = flag_versions.get("muslc_versions", []),
             osx_versions = flag_versions.get("osx_versions", []),
@@ -317,14 +317,13 @@ def render_multiplatform_pkg_aliases(*, aliases, default_version = None, **kwarg
     contents["_config/BUILD.bazel"] = _render_config_settings(**flag_versions)
     return contents
 
-def multiplatform_whl_aliases(*, aliases, default_version = None, **kwargs):
+def multiplatform_whl_aliases(*, aliases, **kwargs):
     """convert a list of aliases from filename to config_setting ones.
 
     Args:
         aliases: list(whl_alias): The aliases to process. Any aliases that have
             the filename set will be converted to a list of aliases, each with
             an appropriate config_setting value.
-        default_version: string | None, the default python version to use.
         **kwargs: Extra parameters passed to get_filename_config_settings.
 
     Returns:
@@ -344,7 +343,6 @@ def multiplatform_whl_aliases(*, aliases, default_version = None, **kwargs):
             filename = alias.filename,
             target_platforms = alias.target_platforms,
             python_version = alias.version,
-            python_default = default_version == alias.version,
             **kwargs
         )
 
@@ -511,8 +509,7 @@ def get_filename_config_settings(
         glibc_versions,
         muslc_versions,
         osx_versions,
-        python_version = "",
-        python_default = True):
+        python_version):
     """Get the filename config settings.
 
     Args:
@@ -522,7 +519,6 @@ def get_filename_config_settings(
         muslc_versions: list[tuple[int, int]], list of versions.
         osx_versions: list[tuple[int, int]], list of versions.
         python_version: the python version to generate the config_settings for.
-        python_default: if we should include the setting when python_version is not set.
 
     Returns:
         A tuple:
@@ -573,28 +569,19 @@ def get_filename_config_settings(
         prefixes = ["sdist"]
         suffixes = [_non_versioned_platform(p) for p in target_platforms or []]
 
-    if python_default and python_version:
-        prefixes += ["cp{}_{}".format(python_version, p) for p in prefixes]
-    elif python_version:
-        prefixes = ["cp{}_{}".format(python_version, p) for p in prefixes]
-    elif python_default:
-        pass
-    else:
-        fail("BUG: got no python_version and it is not default")
-
     versioned = {
-        ":is_{}_{}".format(p, suffix): {
-            version: ":is_{}_{}".format(p, setting)
+        ":is_cp{}_{}_{}".format(python_version, p, suffix): {
+            version: ":is_cp{}_{}_{}".format(python_version, p, setting)
             for version, setting in versions.items()
         }
         for p in prefixes
         for suffix, versions in setting_supported_versions.items()
     }
 
     if suffixes or versioned:
-        return [":is_{}_{}".format(p, s) for p in prefixes for s in suffixes], versioned
+        return [":is_cp{}_{}_{}".format(python_version, p, s) for p in prefixes for s in suffixes], versioned
     else:
-        return [":is_{}".format(p) for p in prefixes], setting_supported_versions
+        return [":is_cp{}_{}".format(python_version, p) for p in prefixes], setting_supported_versions
 
 def _whl_config_setting_suffixes(
         platform_tag,