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bazel_clang_tidy

Run clang-tidy on Bazel C++ targets directly, without generating a compile commands database, and take advantage of Bazels powerful cache mechanism.

Usage:

# //:WORKSPACE
load(
    "@bazel_tools//tools/build_defs/repo:git.bzl",
    "git_repository",
)

git_repository(
       name = "bazel_clang_tidy",
       commit = "69aa13e6d7cf102df70921c66be15d4592251e56",
       remote = "https://github.com/erenon/bazel_clang_tidy.git",
)

You can now compile using the default clang tidy configuration provided using the following command;

bazel build //... \
  --aspects @bazel_clang_tidy//clang_tidy:clang_tidy.bzl%clang_tidy_aspect \
  --output_groups=report

If you would like to override the default clang tidy configuration then you can reconfigure the default target from the command line. To do this you must first make a filegroup target that has the .clang-tidy config file as a data dependency.

# //:BUILD
filegroup(
       name = "clang_tidy_config",
       data = [".clang-tidy"],
       visibility = ["//visibility:public"],
)

Now you can override the default config file in this repository using a command line flag;

bazel build //... \
  --aspects @bazel_clang_tidy//clang_tidy:clang_tidy.bzl%clang_tidy_aspect \
  --output_groups=report \
  --@bazel_clang_tidy//:clang_tidy_config=//:clang_tidy_config

Now if you don't want to type this out every time, it is recommended that you add a config in your .bazelrc that matches this command line;

# Required for bazel_clang_tidy to operate as expected
build:clang-tidy --aspects @bazel_clang_tidy//clang_tidy:clang_tidy.bzl%clang_tidy_aspect
build:clang-tidy --output_groups=report

# Optionally override the .clang-tidy config file target
build:clang-tidy --@bazel_clang_tidy//:clang_tidy_config=//:clang_tidy_config

Now from the command line this is a lot nicer to use;

bazel build //... --config clang-tidy

Features

  • Run clang-tidy on any C++ target
  • Run clang-tidy without also building the target
  • Use Bazel to cache clang-tidy reports: recompute stale reports only

Install

Copy .clang-tidy, BUILD and clang_tidy dir to your workspace. Edit .clang-tidy as needed.

Example

To see the tool in action:

  1. Clone the repository

  2. Run clang-tidy:

    bazel build //example:app --aspects clang_tidy/clang_tidy.bzl%clang_tidy_aspect --output_groups=report

  3. Check the error:

    lib.cpp:4:43: error: the parameter 'name' is copied for each invocation but only used as a const reference; consider making it a const reference [performance-unnecessary-value-param,-warnings-as-errors] std::string lib_get_greet_for(std::string name)
Aspect //clang_tidy:clang_tidy.bzl%clang_tidy_aspect of //example:app failed to build

  4. Fix the error by changing lib.cpp only.

  5. Re-run clang-tidy with the same command. Observe that it does not run clang-tidy for app.cpp: the cached report is re-used.

Requirements

  • Bazel 4.0 or newer (might work with older versions)
  • clang-tidy on $PATH. (if not, edit run_clang_tidy.sh)