clang-tidy

clang-tidy is a linter for Protobuf and C, C++.

You can enable the clang-tidy linter with:

trunk check enable clang-tidy

Auto Enabling

clang-tidy will be auto-enabled if a .clang-tidy config file is present.

Settings

clang-tidy supports the following config files:

.clang-tidy

You can move these files to .trunk/configs and trunk check will still find them. See Moving Linters for more info. Trunk Code Quality provides a default .clang-tidy if your project does not already have one.

Usage Notes

We only support using clang-tidy from Bazel and CMake projects.

In order to only see issues in your own code, not from library header files your code includes, add this to your .clang-tidy file:

HeaderFilterRegex: \./.+

You may have to build your project first if you depend on any generated header files.

Linter Failures

If a file you're linting does not compile, clang-tidy may fail to process it. In trunk, this will show up as a Linter Failure. The output you'll see will look like a compilation error. This can also happen if the pre-reqs to running clang-tidy haven't been met (see below).

Using Bazel

By default Trunk will query bazel for compile commands used to run clang-tidy. This requires no configuration.

Trunk will build needed compilation pre-requisites before invoking clang-tidy on each file (e.g. generated protobuf headers).

You can generate a local compilation database by running trunk generate-compile-commands.

Finding the bazel binary

Trunk will search for the bazel binary in two ways.

Paths relative to the workspace root.
Binaries in any of the directories in the PATH environment variable.

First trunk will search all workspace root relative paths and then all system directories. If you override anything in lint.bazel.paths then we only search the paths you specify. By default the configuration is as follows.

lint:
  bazel:
    paths:
      workspace:
        - tools/bazel
        - bazelisk
      system:
        - bazel
        - bazelisk

Using `compile_commands.json` generated by CMake

Trunk supports using the compile_commands.json file generated by CMake. If you run cmake from a directory called build in the root of your project then Trunk will find the compile commands automatically. If you run it in some other directory then you will have to symlink the compile_commands.json in that directory to the root of your repo for trunk to find them. Note that Trunk does not currently support CMake out of tree builds.

Another tool claims I have clang-tidy issues, but not Trunk. What gives?

Trunk runs clang-tidy with a compile commands database so that we can guarantee clang-tidy produces the correct diagnostics about your code. Other tools, such as clangd, may use best-effort heuristics to guess a compile command for a given clang-tidy input file (for example, see this discussion) and consequently produce incorrect clang-tidy findings because they guessed the compile command wrong.