chore: stop exposing config settings in the toolchain aliases repo

Author: aignas

python/private/toolchain_aliases.bzl

@@ -0,0 +1,45 @@
+# Copyright 2024 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.
+
+"""Create toolchain alias targets."""
+
+load("@rules_python//python:versions.bzl", "PLATFORMS")
+
+def toolchain_aliases(*, name, platforms, native = native):
+    """Cretae toolchain aliases for the python toolchains.
+
+    Args:
+        name: {type}`str` The name of the current repository.
+        platforms: {type}`platforms` The list of platforms that are supported
+            for the current toolchain repository.
+        native: The native struct used in the macro, useful for testing.
+    """
+    for platform in PLATFORMS.keys():
+        if platform not in platforms:
+            continue
+
+        native.config_setting(
+            name = platform,
+            flag_values = PLATFORMS[platform].flag_values,
+            constraint_values = PLATFORMS[platform].compatible_with,
+            visibility = ["//visibility:private"],
+        )
+
+    native.alias(name = "files", actual = select({{":" + item: "@" + name + "_" + item + "//:files" for item in platforms}}))
+    native.alias(name = "includes", actual = select({{":" + item: "@" + name + "_" + item + "//:includes" for item in platforms}}))
+    native.alias(name = "libpython", actual = select({{":" + item: "@" + name + "_" + item + "//:libpython" for item in platforms}}))
+    native.alias(name = "py3_runtime", actual = select({{":" + item: "@" + name + "_" + item + "//:py3_runtime" for item in platforms}}))
+    native.alias(name = "python_headers", actual = select({{":" + item: "@" + name + "_" + item + "//:python_headers" for item in platforms}}))
+    native.alias(name = "python_runtimes", actual = select({{":" + item: "@" + name + "_" + item + "//:python_runtimes" for item in platforms}}))
+    native.alias(name = "python3", actual = select({{":" + item: "@" + name + "_" + item + "//:" + ("python.exe" if "windows" in item else "bin/python3") for item in platforms}}))

python/private/toolchains_repo.bzl

@@ -135,20 +135,16 @@ def _toolchain_aliases_impl(rctx):
     build_contents = """\
 # Generated by python/private/toolchains_repo.bzl
 package(default_visibility = ["//visibility:public"])
-load("@rules_python//python:versions.bzl", "gen_python_config_settings")
-gen_python_config_settings()
+load("@rules_python//python/private:toolchain_aliases.bzl", "toolchain_aliases")
 exports_files(["defs.bzl"])
 
 PLATFORMS = [
 {loaded_platforms}
 ]
-alias(name = "files",           actual = select({{":" + item: "@{py_repository}_" + item + "//:files" for item in PLATFORMS}}))
-alias(name = "includes",        actual = select({{":" + item: "@{py_repository}_" + item + "//:includes" for item in PLATFORMS}}))
-alias(name = "libpython",       actual = select({{":" + item: "@{py_repository}_" + item + "//:libpython" for item in PLATFORMS}}))
-alias(name = "py3_runtime",     actual = select({{":" + item: "@{py_repository}_" + item + "//:py3_runtime" for item in PLATFORMS}}))
-alias(name = "python_headers",  actual = select({{":" + item: "@{py_repository}_" + item + "//:python_headers" for item in PLATFORMS}}))
-alias(name = "python_runtimes", actual = select({{":" + item: "@{py_repository}_" + item + "//:python_runtimes" for item in PLATFORMS}}))
-alias(name = "python3",         actual = select({{":" + item: "@{py_repository}_" + item + "//:" + ("python.exe" if "windows" in item else "bin/python3") for item in PLATFORMS}}))
+toolchain_aliases(
+    name = "{py_repository}",
+    platforms = PLATFORMS,
+)
 """.format(
         py_repository = rctx.attr.user_repository_name,
         loaded_platforms = "\n".join(["    \"{}\",".format(p) for p in rctx.attr.platforms]),