how_to_add_an_external_dependency.md

How to Add a New External Dependency

The design and implementation goal is to minimize the dependency that must be pre-installed in the system. If your target depends on a module for which you have to apt-get install first, consider using Bazel as the package/dependency management system.

For example, if you want to add a workspace rule foo that is not originally built with Bazel, do the following:

• Add a workspace rule named 'foo' in the WORKSPACE file.
• Specify the source of foo (usually a URL), and the version (usually a commit hash or a git tag).
• Write a foo.BUILD under the third_party directory to build it. The BUILD file will be similar to any other Bazel BUILD file of your own targets.
• In your target that depends on foo, put @foo://:<foo_target> in its dependencies.

Use Bazel to Add an External Dependency

If you add a workspace rule foo using Bazel to build your target, depending on foo, Bazel pulls the source code of foo from the source specified, and builds it with foo.BUILD. If foo was originally built with Bazel, then only the workspace rule is needed.

References

For a detailed description on adding a dependency with Bazel, refer to the following:

• Workspace Rules
• Working with external dependencies.