bazel_clang_format

Run clang-format on Bazel C++ targets directly. It's like bazel_clang_tidy but for clang-format.

usage

Update your project with

# //:WORKSPACE.bazel
load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_repository")

BAZEL_CLANG_FORMAT_COMMIT = ...

http_repository(
    name = "bazel_clang_format",
    integrity = ...,
    strip_prefix = "bazel_clang_format-{commit}".format(
        commit = BAZEL_CLANG_FORMAT_COMMIT,
    ),
    url = "https://github.com/oliverlee/bazel_clang_format/archive/{commit}.tar.gz".format(
        commit = BAZEL_CLANG_FORMAT_COMMIT,
    ),
)

# //:.bazelrc
build:clang-format --aspects=@bazel_clang_format//:defs.bzl%check_aspect
build:clang-format --output_groups=report

build:clang-format-fix --aspects=@bazel_clang_format//:defs.bzl%fix_aspect
build:clang-format-fix --output_groups=report
build:clang-format-fix --use_action_cache=false

Check formatting with

bazel build //... --config=clang-format

Fix formatting with

bazel build //... --config=clang-format-fix

This will use clang-format in your PATH and .clang-format defined in this repo.

using a hermetic toolchain

To specify a specific binary (e.g. clang-format is specified by a hermetic toolchain like this), update the build setting in .bazelrc.

# //:.bazelrc
build:clang-format-base --output_groups=report
build:clang-format-base --@bazel_clang_format//:binary=@llvm18//:clang-format

build:clang-format --aspects=@bazel_clang_format//:defs.bzl%check_aspect

build:clang-format-fix --aspects=@bazel_clang_format//:defs.bzl%fix_aspect
build:clang-format-fix --use_action_cache=false

specifying .clang-format

To override the default .clang-format, define a filegroup containing the replacement config and update build setting in .bazelrc.

# //:BUILD.bazel

load("@bazel_clang_format//:defs.bzl")

filegroup(
    name = "clang-format-config",
    srcs = [".clang-format"],
    visibility = ["//visibility:public"],
)

# //:.bazelrc
build:clang-format-base --output_groups=report
build:clang-format-base --@bazel_clang_format//:config=//:clang-format-config
...

ignoring certain targets

Formatting can be skipped for certain targets by specifying a filegroup

# //:BUILD.bazel

filegroup(
    name = "clang-format-ignore",
    srcs = [
       "//third_party/lib1",
       "//third_party/lib2",
    ],
)

# //:.bazelrc

build:clang-format-base --output_groups=report
build:clang-format-base --@bazel_clang_format//:ignore=//:clang-format-ignore
...

Requirements

• Bazel 5.x
• ClangFormat 14