refactor(toolchain): use a helper method to convert an X.Y version to X.Y.Z (#1423)

Before this PR in numerous places we would check the MINOR_MAPPING dict.
This PR adds a function that also fails if the X.Y format is not in the
MINOR_MAPPING dict making the code more robust.

Split from #1340 to unblock #1364.

---------

Co-authored-by: Thulio Ferraz Assis <[email protected]>

Author: aignas

python/extensions/private/pythons_hub.bzl

@@ -14,7 +14,8 @@
 
 "Repo rule used by bzlmod extension to create a repo that has a map of Python interpreters and their labels"
 
-load("//python:versions.bzl", "MINOR_MAPPING", "WINDOWS_NAME")
+load("//python:versions.bzl", "WINDOWS_NAME")
+load("//python/private:full_version.bzl", "full_version")
 load(
     "//python/private:toolchains_repo.bzl",
     "get_host_os_arch",
@@ -28,12 +29,6 @@ def _have_same_length(*lists):
         fail("expected at least one list")
     return len({len(length): None for length in lists}) == 1
 
-def _get_version(python_version):
-    # we need to get the MINOR_MAPPING or use the full version
-    if python_version in MINOR_MAPPING:
-        python_version = MINOR_MAPPING[python_version]
-    return python_version
-
 def _python_toolchain_build_file_content(
         prefixes,
         python_versions,
@@ -55,7 +50,7 @@ def _python_toolchain_build_file_content(
     # build the toolchain content by calling python_toolchain_build_file_content
     return "\n".join([python_toolchain_build_file_content(
         prefix = prefixes[i],
-        python_version = _get_version(python_versions[i]),
+        python_version = full_version(python_versions[i]),
         set_python_version_constraint = set_python_version_constraints[i],
         user_repository_name = user_repository_names[i],
         rules_python = rules_python,

python/pip.bzl

@@ -17,8 +17,8 @@ load("//python/pip_install:pip_repository.bzl", "pip_repository", _package_annot
 load("//python/pip_install:repositories.bzl", "pip_install_dependencies")
 load("//python/pip_install:requirements.bzl", _compile_pip_requirements = "compile_pip_requirements")
 load("//python/private:bzlmod_enabled.bzl", "BZLMOD_ENABLED")
+load("//python/private:full_version.bzl", "full_version")
 load("//python/private:render_pkg_aliases.bzl", "NO_MATCH_ERROR_MESSAGE_TEMPLATE")
-load(":versions.bzl", "MINOR_MAPPING")
 
 compile_pip_requirements = _compile_pip_requirements
 package_annotation = _package_annotation
@@ -295,7 +295,7 @@ alias(
     for [python_version, repo_prefix] in version_map:
         alias.append("""\
         "@{rules_python}//python/config_settings:is_python_{full_python_version}": "{actual}",""".format(
-            full_python_version = MINOR_MAPPING[python_version] if python_version in MINOR_MAPPING else python_version,
+            full_python_version = full_version(python_version),
             actual = "@{repo_prefix}{wheel_name}//:{alias_name}".format(
                 repo_prefix = repo_prefix,
                 wheel_name = wheel_name,

python/private/full_version.bzl

@@ -0,0 +1,43 @@
+# Copyright 2023 The Bazel Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""A small helper to ensure that we are working with full versions."""
+
+load("//python:versions.bzl", "MINOR_MAPPING")
+
+def full_version(version):
+    """Return a full version.
+
+    Args:
+        version: the version in `X.Y` or `X.Y.Z` format.
+
+    Returns:
+        a full version given the version string. If the string is already a
+        major version then we return it as is.
+    """
+    if version in MINOR_MAPPING:
+        return MINOR_MAPPING[version]
+
+    parts = version.split(".")
+    if len(parts) == 3:
+        return version
+    elif len(parts) == 2:
+        fail(
+            "Unknown Python version '{}', available values are: {}".format(
+                version,
+                ",".join(MINOR_MAPPING.keys()),
+            ),
+        )
+    else:
+        fail("Unknown version format: {}".format(version))

python/repositories.bzl

@@ -21,6 +21,7 @@ load("@bazel_tools//tools/build_defs/repo:http.bzl", _http_archive = "http_archi
 load("@bazel_tools//tools/build_defs/repo:utils.bzl", "maybe", "read_netrc", "read_user_netrc", "use_netrc")
 load("//python/private:bzlmod_enabled.bzl", "BZLMOD_ENABLED")
 load("//python/private:coverage_deps.bzl", "coverage_dep")
+load("//python/private:full_version.bzl", "full_version")
 load("//python/private:internal_config_repo.bzl", "internal_config_repo")
 load(
     "//python/private:toolchains_repo.bzl",
@@ -32,7 +33,6 @@ load("//python/private:which.bzl", "which_with_fail")
 load(
     ":versions.bzl",
     "DEFAULT_RELEASE_BASE_URL",
-    "MINOR_MAPPING",
     "PLATFORMS",
     "TOOL_VERSIONS",
     "get_release_info",
@@ -534,8 +534,7 @@ def python_register_toolchains(
 
     base_url = kwargs.pop("base_url", DEFAULT_RELEASE_BASE_URL)
 
-    if python_version in MINOR_MAPPING:
-        python_version = MINOR_MAPPING[python_version]
+    python_version = full_version(python_version)
 
     toolchain_repo_name = "{name}_toolchains".format(name = name)