From a14808554e926227b9d4e0d2015857f842e40447 Mon Sep 17 00:00:00 2001
From: Xavier Bonaventura <xavier.bonaventura@bmw.de>
Date: Thu, 13 Nov 2025 10:07:22 +0100
Subject: [PATCH] Add support to inject cc_feature into legacy toolchains

This adds a parameter to unix cc_toolchain_config and windows
cc_toolchain_config to be able to inject a cc_feature.
This allows a user to inject a feature (for example for custom
warnings) without having to reimplement the full toolchain.

Resolves #517
---
 .../toolchain/unix_cc_toolchain_config.bzl    |  4 ++++
 .../toolchain/windows_cc_toolchain_config.bzl |  7 ++++++-
 cc/toolchains/feature_injection.bzl           | 20 +++++++++++++++++++
 3 files changed, 30 insertions(+), 1 deletion(-)
 create mode 100644 cc/toolchains/feature_injection.bzl

diff --git a/cc/private/toolchain/unix_cc_toolchain_config.bzl b/cc/private/toolchain/unix_cc_toolchain_config.bzl
index f91fa3f1..ea3f5575 100644
--- a/cc/private/toolchain/unix_cc_toolchain_config.bzl
+++ b/cc/private/toolchain/unix_cc_toolchain_config.bzl
@@ -31,6 +31,7 @@ load(
 )
 load("@rules_cc//cc/common:cc_common.bzl", "cc_common")
 load("@rules_cc//cc/toolchains:cc_toolchain_config_info.bzl", "CcToolchainConfigInfo")
+load("@rules_cc//cc/toolchains:feature_injection.bzl", "FeatureInfo", "convert_feature")
 
 def _target_os_version(ctx):
     platform_type = ctx.fragments.apple.single_arch_platform.platform_type
@@ -1950,6 +1951,8 @@ def _impl(ctx):
     if symbol_check:
         features.append(symbol_check)
 
+    features.extend([convert_feature(extra_feature[FeatureInfo]) for extra_feature in ctx.attr.extra_features])
+
     return cc_common.create_cc_toolchain_config_info(
         ctx = ctx,
         features = features,
@@ -1985,6 +1988,7 @@ cc_toolchain_config = rule(
         "cxx_builtin_include_directories": attr.string_list(),
         "cxx_flags": attr.string_list(),
         "dbg_compile_flags": attr.string_list(),
+        "extra_features": attr.label_list(providers = [FeatureInfo], default = []),
         "extra_flags_per_feature": attr.string_list_dict(),
         "fastbuild_compile_flags": attr.string_list(),
         "host_system_name": attr.string(mandatory = True),
diff --git a/cc/private/toolchain/windows_cc_toolchain_config.bzl b/cc/private/toolchain/windows_cc_toolchain_config.bzl
index 5fa087e5..a5df2035 100644
--- a/cc/private/toolchain/windows_cc_toolchain_config.bzl
+++ b/cc/private/toolchain/windows_cc_toolchain_config.bzl
@@ -31,6 +31,7 @@ load(
 )
 load("@rules_cc//cc/common:cc_common.bzl", "cc_common")
 load("@rules_cc//cc/toolchains:cc_toolchain_config_info.bzl", "CcToolchainConfigInfo")
+load("@rules_cc//cc/toolchains:feature_injection.bzl", "FeatureInfo", "convert_feature")
 
 all_compile_actions = [
     ACTION_NAMES.c_compile,
@@ -1703,9 +1704,12 @@ def _impl(ctx):
         ],
         enabled = True,
     )
+    features.extend([cpp_modules_feature, cpp_module_modmap_file_feature, cpp20_module_compile_flags_feature])
+    features.extend([convert_feature(extra_feature[FeatureInfo]) for extra_feature in ctx.attr.extra_features])
+
     return cc_common.create_cc_toolchain_config_info(
         ctx = ctx,
-        features = features + [cpp_modules_feature, cpp_module_modmap_file_feature, cpp20_module_compile_flags_feature],
+        features = features,
         action_configs = action_configs,
         artifact_name_patterns = artifact_name_patterns,
         cxx_builtin_include_directories = ctx.attr.cxx_builtin_include_directories,
@@ -1736,6 +1740,7 @@ cc_toolchain_config = rule(
         "dbg_mode_debug_flag": attr.string(default = ""),
         "default_compile_flags": attr.string_list(default = []),
         "default_link_flags": attr.string_list(default = []),
+        "extra_features": attr.label_list(providers = [FeatureInfo], default = []),
         "fastbuild_mode_debug_flag": attr.string(default = ""),
         "host_system_name": attr.string(),
         "link_flags": attr.string_list(),
diff --git a/cc/toolchains/feature_injection.bzl b/cc/toolchains/feature_injection.bzl
new file mode 100644
index 00000000..44ca300e
--- /dev/null
+++ b/cc/toolchains/feature_injection.bzl
@@ -0,0 +1,20 @@
+# Copyright 2026 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.
+"""Provides necessary tools to inject rules-based features to legacy toolchains"""
+
+load("@rules_cc//cc/toolchains:cc_toolchain_info.bzl", _FeatureInfo = "FeatureInfo")
+load("@rules_cc//cc/toolchains/impl:legacy_converter.bzl", _convert_feature = "convert_feature")
+
+convert_feature = _convert_feature
+FeatureInfo = _FeatureInfo