bazel: Enable the layering check by default

However, disable it for any package which currently does not build with
the layering check enabled. We will burn down this list, but enabling
the layering check for those modules that do build with it will prevent
backsliding.

I decided to disable the check on a package-by-package basis because
digging down into the targets seemed too finnicky. This way, the
workflow for the OWNERS of the individual modules (which approximately
correspond to packages) is to remove one line, get the compiler to be
happy, and send a CL.

This change was auto-generated by buildifier (see bug for details),
except for changes to the following files:

* .bazelrc
* REPO.bazel
* pw_fuzzer/fuzztest.bazelrc
* pw_toolchain/host_clang/BUILD.bazel

Bug: 219091175
Change-Id: Ie9a39620ffdd5fd1406b9d38145e3530f4479c5e
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/261293
Commit-Queue: Ted Pudlik <tpudlik@google.com>
Docs-Not-Needed: Ted Pudlik <tpudlik@google.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Reviewed-by: Armando Montanez <amontanez@google.com>

.bazelrc

@@ -92,6 +92,17 @@ build --features=internal_strict_warnings
 coverage --experimental_generate_llvm_lcov
 coverage --combined_report=lcov
 
+# Enable layering check support.
+#
+# NOTE: this _does not_ by itself enable the layering check; that's done in
+# REPO.bazel. This flag only ensures the module maps for sysroot and toolchain
+# headers (needed for the layering check to not produce false positives) are
+# constructed. Module map construction is gated behind a flag because the
+# approach we take does not work in Bazel versions older than 8.0.0, so some
+# downstream projects using Pigweed's toolchains would be broken if this flag
+# was removed and always set to true in the toolchain definition.
+common --//pw_toolchain/host_clang:layering_check
+
 # Java related flags
 # ==================
 # Workaround for https://github.com/bazelbuild/rules_jvm_external/issues/445.
@@ -194,6 +205,9 @@ build:microbit --platforms=//targets/microbit
 common:googletest --//pw_unit_test:backend=//pw_unit_test:googletest
 common:googletest --//pw_unit_test:main=@com_google_googletest//:gtest_main
 common:googletest --platforms=//pw_unit_test:googletest_platform
+# TODO: https://pwbug.dev/390709187 - Re-enable layering check once the layering
+# issues in the googletest backend are fixed.
+common:googletest --features=-layering_check
 
 # Remote execution config definitions
 # ===================================

REPO.bazel

@@ -0,0 +1,26 @@
+# Copyright 2025 The Pigweed Authors
+#
+# 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
+#
+#     https://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.
+"""Repository-wide configuration for Pigweed.
+
+See https://bazel.build/external/overview#repo.bazel. This file is used in
+particular to enable toolchain features that we want to enable for all Pigweed
+targets, but not for any external dependencies also compiled with Bazel.
+"""
+
+repo(
+    # Any C++ toolchain features enabled here will be enabled when compiling
+    # Pigweed, but not when compiling any dependencies hosted in external
+    # repositories.
+    features = ["layering_check"],
+)

pw_allocator/BUILD.bazel

@@ -16,7 +16,10 @@ load("@rules_python//sphinxdocs:sphinx_docs_library.bzl", "sphinx_docs_library")
 load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_allocator/benchmarks/BUILD.bazel

@@ -17,7 +17,10 @@ load(
     "pw_cc_test",
 )
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_allocator/block/BUILD.bazel

@@ -14,7 +14,10 @@
 
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_allocator/bucket/BUILD.bazel

@@ -14,7 +14,10 @@
 
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_allocator/examples/BUILD.bazel

@@ -17,7 +17,10 @@ load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 load("//pw_build:pw_cc_binary.bzl", "pw_cc_binary")
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_allocator/size_report/BUILD.bazel

@@ -14,7 +14,10 @@
 
 load("//pw_build:pw_cc_binary.bzl", "pw_cc_binary")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_assert_log/BUILD.bazel

@@ -15,7 +15,10 @@
 load("@rules_python//sphinxdocs:sphinx_docs_library.bzl", "sphinx_docs_library")
 load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_assert_tokenized/BUILD.bazel

@@ -15,7 +15,10 @@
 load("@rules_python//sphinxdocs:sphinx_docs_library.bzl", "sphinx_docs_library")
 load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_async/BUILD.bazel

@@ -17,7 +17,10 @@ load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 load("//pw_build:pw_facade.bzl", "pw_facade")
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_async2/BUILD.bazel

@@ -20,7 +20,10 @@ load(
 )
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_async2/examples/BUILD.bazel

@@ -17,7 +17,10 @@ load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 load("//pw_build:pw_cc_binary.bzl", "pw_cc_binary")
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_async2_basic/BUILD.bazel

@@ -15,7 +15,10 @@
 load("@rules_python//sphinxdocs:sphinx_docs_library.bzl", "sphinx_docs_library")
 load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_async2_epoll/BUILD.bazel

@@ -15,7 +15,10 @@
 load("@rules_python//sphinxdocs:sphinx_docs_library.bzl", "sphinx_docs_library")
 load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_async_basic/BUILD.bazel

@@ -16,7 +16,10 @@ load("@rules_python//sphinxdocs:sphinx_docs_library.bzl", "sphinx_docs_library")
 load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_async_basic/size_report/BUILD.bazel

@@ -14,6 +14,8 @@
 
 load("//pw_build:pw_cc_binary.bzl", "pw_cc_binary")
 
+package(features = ["-layering_check"])
+
 licenses(["notice"])
 
 pw_cc_binary(

pw_blob_store/BUILD.bazel

@@ -16,7 +16,10 @@ load("@rules_python//sphinxdocs:sphinx_docs_library.bzl", "sphinx_docs_library")
 load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_blob_store/size_report/BUILD.bazel

@@ -14,7 +14,10 @@
 
 load("//pw_build:pw_cc_binary.bzl", "pw_cc_binary")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_bluetooth/BUILD.bazel

@@ -17,7 +17,10 @@ load("@rules_python//sphinxdocs:sphinx_docs_library.bzl", "sphinx_docs_library")
 load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_bluetooth_hci/BUILD.bazel

@@ -17,7 +17,10 @@ load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 load("//pw_fuzzer:fuzzer.bzl", "pw_cc_fuzz_test")
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_bluetooth_profiles/BUILD.bazel

@@ -16,7 +16,10 @@ load("@rules_python//sphinxdocs:sphinx_docs_library.bzl", "sphinx_docs_library")
 load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_bluetooth_proxy/BUILD.bazel

@@ -16,7 +16,10 @@ load("@rules_python//sphinxdocs:sphinx_docs_library.bzl", "sphinx_docs_library")
 load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_bluetooth_proxy/size_report/BUILD.bazel

@@ -14,7 +14,10 @@
 
 load("//pw_build:pw_cc_binary.bzl", "pw_cc_binary")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 licenses(["notice"])
 

pw_bluetooth_sapphire/BUILD.bazel

@@ -16,7 +16,10 @@ load("@rules_python//sphinxdocs:sphinx_docs_library.bzl", "sphinx_docs_library")
 load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//pw_bluetooth_sapphire:__subpackages__"])
+package(
+    default_visibility = ["//pw_bluetooth_sapphire:__subpackages__"],
+    features = ["-layering_check"],
+)
 
 cc_library(
     name = "config",

pw_bluetooth_sapphire/host/BUILD.bazel

@@ -14,7 +14,10 @@
 
 # Note, this file is not copybara'd from upstream Fuchsia.
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 cc_library(
     name = "stack",

pw_bluetooth_sapphire/host/att/BUILD.bazel

@@ -16,7 +16,10 @@ load("@rules_python//sphinxdocs:sphinx_docs_library.bzl", "sphinx_docs_library")
 load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 # Basic target with protocol definitions and no logic, suitable for test
 # emulation.

pw_bluetooth_sapphire/host/common/BUILD.bazel

@@ -15,7 +15,10 @@
 load("//pw_fuzzer:fuzzer.bzl", "pw_cc_fuzz_test")
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 cc_library(
     name = "common",

pw_bluetooth_sapphire/host/gap/BUILD.bazel

@@ -17,7 +17,10 @@ load("//pw_build:compatibility.bzl", "incompatible_with_mcu")
 load("//pw_fuzzer:fuzzer.bzl", "pw_cc_fuzz_test")
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 cc_library(
     name = "definitions",

pw_bluetooth_sapphire/host/gatt/BUILD.bazel

@@ -14,7 +14,10 @@
 
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 # Basic target with protocol definitions and no logic, suitable for test
 # emulation.

pw_bluetooth_sapphire/host/hci-spec/BUILD.bazel

@@ -14,7 +14,10 @@
 
 load("//pw_unit_test:pw_cc_test.bzl", "pw_cc_test")
 
-package(default_visibility = ["//visibility:public"])
+package(
+    default_visibility = ["//visibility:public"],
+    features = ["-layering_check"],
+)
 
 cc_library(
     name = "hci-spec",