Clang-tidy

rules_ll includes a Bazel overlay for clang-tidy. The ll_compilation_database rule creates a compilation database for a target and its dependencies. Running that rule invokes clang-tidy on it.

You can find similar examples to the ones in this guide at rules_ll/examples/clang_tidy_example.

Usage

For a target my_library defined in a BUILD.bazel file, add an ll_compilation_database like this:

BUILD.bazel

load("@rules_ll//ll:defs.bzl", "ll_library", "ll_compilation_database")

filegroup(
   name = "clang_tidy_config",
   srcs = [".clang-tidy"],
)

ll_library(
    name = "my_library",
    srcs = ["my_library.cpp"],
)

ll_compilation_database(
    name = "my_library_compile_commands",
    targets = [":my_library"],
    config = ":clang_tidy_config",
)

The targets attribute in ll_compilation_database declares the targets included in the compile_commands.json file.

The .clang-tidy file configures clang-tidy. See rules_ll/examples/.clang-tidy for an example.

To run clang-tidy on the sources of my_library_compile_commands, run

bazel run my_library_compile_commands
# Prints warnings for my_library.cpp.

If you require a compile_commands.json file for using it with an IDE, you can build instead of run the compile_commands target and locate the compile_commands.json file in the bazel-bin directory.

bazel build my_library_compile_commands
# Output in bazel-bin/k8-fastbuild/bin

This builds a file named compile_commands.json, regardless of the ll_compilation_database target's name attribute.

Compilation databases

The ll_compilation_database rule constructs the compile_commands.json file from all targets needed to build the targets in the targets attribute. Consider the following targets:

BUILD.bazel

filegroup(
   name = "clang_tidy_config",
   srcs = [".clang-tidy"],
)

ll_library(
    name = "mylib_1",
    srcs = [
        "mylib_1.cpp",
        "mylib_1_additional_source.cpp",
    ]
)

ll_library(
    name = "mylib_2",
    srcs = "mylib_2.cpp",
    deps = [
        ":mylib_1",
    ]
)

ll_compilation_database(
    name = "cdb_1",
    targets = [":mylib_1"],
    config = ":clang_tidy_config",
)

ll_compilation_database(
    name = "cdb_2",
    targets = [":mylib_2"],
    config = ":clang_tidy_config",
)

ll_compilation_database(
   name = "compile_commands",
   targets = [
      ":mylib_1",
      ":mylib_2",
   ],
   config = ":clang_tidy_config",
)

Running cdb_1 invokes clang-tidy on mylib_1.cpp alone:

bazel run cdb_1
# Prints warnings for mylib_1.cpp and mylib_1_additional_source.cpp.

Running cdb_2 invokes clang-tidy on mylib_1.cpp and mylib_2.cpp:

bazel run cdb_2
# Prints warnings for mylib_1.cpp, mylib_2.cpp and
# mylib_1_additional_source.cpp.

Running compile_commands also invokes clang-tidy on both targets.

Limitations

The ll_compilation_database rule doesn't support the -fix option for clang-tidy. The auto fixer tends to break code and would have to work outside of the Bazel build directories.