This page covers how to start contributing code to Bazel. It covers how to set up your coding environment, describes creating an IntelliJ project and takes you through compiling and debugging your project.
After you set up your environment, there is a quick overview of the structure of Bazel’s code base, how to search and navigate the code, and how to monitor your builds with Bazel’s continuous integration system.
Before you start developing, you’ll need to:
Install the latest version of Bazel on your system. For instructions, see Compiling Bazel from source.
Clone Bazel’s Git repository from GitHub:
git clone https://github.com/bazelbuild/bazel.git
Install any missing prerequisites.
Try to build Bazel:
On Linux/macOS, in Bash/Terminal:
cd bazel bazel build //src:bazel
On Windows, in the Command Prompt:
cd bazel bazel --output_user_root=c:\tmp build //src:bazel.exe
For faster iteration times (but larger binaries), use
This produces a working Bazel binary in
bazel-bin/src/bazel.exe on Windows).
Creating an IntelliJ project
The IDE that Bazel supports is IntelliJ.
To work with IntelliJ:
- Install Bazel’s IntelliJ plug-in.
- Set the path to the Bazel binary in the plugin preferences
- Import the Bazel workspace as a Bazel project
Import Bazel Project...) with the following settings:
- Use existing Bazel workspace: choose your cloned Git repository.
Import from workspaceand choose the
scripts/ij.bazelprojectfile as the
- Download Google’s Java Code Style Scheme file for IntelliJ,
import it (go to
Import) and use it when working on Bazel’s code.
You need to compile Bazel in order to test it. To compile a development version of Bazel, you need the latest released version of Bazel, which can be compiled from source.
You can build the Bazel binary using
bazel build //src:bazel, using
bazel from your PATH.
The resulting binary can be found at
bazel-bin/src/bazel. This is the
recommended way of rebuilding Bazel once you have bootstrapped it.
In addition to the Bazel binary, you might want to build the various tools Bazel
uses. They are located in
//src/tools/... and their directories contain README files describing their
When modifying Bazel:
- Build a distribution archive with
bazel build //:bazel-distfile.
- Unzip the archive in a new empty directory.
bash compile.sh allthere.
This command rebuilds Bazel with
./compile.sh, Bazel with
compile.sh and Bazel with the Bazel-built binary. It compares if the
constructed Bazel builts are identical and then runs all Bazel tests with
bazel test //src/... //third_party/ijar/.... This is also used internally
to ensure that we don’t break Bazel when pushing new commits.
To create a debug configuration for both C++ and Java in your
build:debug -c dbg build:debug --javacopt="-g" build:debug --copt="-g" build:debug --strip="never"
Rebuild Bazel with
bazel build --config debug //src:bazel and use
your favorite debugger to start debugging.
To debug the C++ client, run it from
lldb as usual.
However, to debug Java code, attach to the server using the following:
- Run Bazel with the debugging option
--host_jvm_debugbefore the command (e.g.,
bazel --host_jvm_debug build //src:bazel).
- Attach a debugger to the port 5005. For instance, with
jdb -attach localhost:5005.
Our IntelliJ plugin has built-in debugging support.
Using Bazel Continuous Integration
Bazel’s code description
Bazel has a large codebase with code in multiple locations.
Bazel is organized as follows:
- Client code is in
src/main/cppand provides the command-line interface.
- Protocol buffers are in
- Server code is in
- Java native interfaces are in
- Various tooling for language support are described in the list in the compiling Bazel section.
For a detailed description of the code base, read CODEBASE.md.
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.