Writing Custom Plugins and Rules

Custom plugin implementations and rule implementations can be written in golang or starlark. Golang implementations are statically compiled into the final gazelle_binary whereas starlark plugins are evaluated at gazelle runtime.

+/- of golang implementations

• + Full power of a statically compiled language, the golang stdlib, and external dependencies.
• + Easier to test.
• + API not experimental.
• - Cannot be used in a proto_repository rule without forking stackb/rules_proto.
• - Initial setup harder, often housed within your own custom gazelle extension.

Until a dedicated tutorial is available, please consult the source code for examples.

+/- of starlark implementations

• + More familiar to developer with starlark experience but not golang.
• + Easier setup (*.star files in your gazelle repository)
• + Possible to use in conjunction with the proto_repository rule.
• - Limited API: can only reference state that has been already configured via gazelle directives.
• - Not possible to implement stateful design.
• - No standard library.

Until a dedicated tutorial is available, please consult the reference example in example/testdata/starlark_java.