Contributing to Bazel

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There are many ways to help the Bazel project and ecosystem.

Provide feedback

As you use Bazel, you may find things that can be improved. You can help by reporting issues when:

  • Bazel crashes or you encounter a bug that can only be resolved using bazel clean.
  • The documentation is incomplete or unclear. You can also report issues from the page you are viewing by using the "Create issue" link at the top right corner of the page.
  • An error message could be improved.

Participate in the community

You can engage with the Bazel community by:

Contribute code

Bazel is a large project and making a change to the Bazel source code can be difficult.

You can contribute to the Bazel ecosystem by:

  • Helping rules maintainers by contributing pull requests.
  • Creating new rules and open-sourcing them.
  • Contributing to Bazel-related tools, for example, migration tools.
  • Improving Bazel integration with other IDEs and tools.

Before making a change, create a GitHub issue or email bazel-dev@.

The most helpful contributions fix bugs or add features (as opposed to stylistic, refactoring, or "cleanup" changes). Your change should include tests and documentation, keeping in mind backward-compatibility, portability, and the impact on memory usage and performance.

To learn about how to submit a change, see the patch acceptance process.

Bazel's code description

Bazel has a large codebase with code in multiple locations. See the codebase guide for more details.

Bazel is organized as follows:

  • Client code is in src/main/cpp and provides the command-line interface.
  • Protocol buffers are in src/main/protobuf.
  • Server code is in src/main/java and src/test/java.
    • Core code which is mostly composed of SkyFrame and some utilities.
    • Built-in rules are in and in You might want to read about the Challenges of Writing Rules first.
  • Java native interfaces are in src/main/native.
  • Various tooling for language support are described in the list in the compiling Bazel section.

Searching Bazel's source code

To quickly search through Bazel's source code, use Bazel Code Search. You can navigate Bazel's repositories, branches, and files. You can also view history, diffs, and blame information. To learn more, see the Bazel Code Search User Guide.