Error Prone supports custom checks via a plugin mechanism. Plugin checks are loaded dynamically from the annotation processor path using java.util.ServiceLoader.

Plugin checks are implemented exactly the same way as the built-in checks, except for the @AutoService(BugChecker.class) annotation:

Plugin checks should work with any build system that allows setting the annotation processor classpath.

java_library(
    name = "demo",
    srcs = ["java/com/example/Demo.java"],
    plugins = [":my_custom_check"],
)

java_plugin(
    name = "my_custom_check",
    srcs = ["java/com/example/MyCustomCheck.java"],
    deps = [
        ":auto_service",
        "@maven//:com_google_errorprone_error_prone_annotation",
        "@maven//:com_google_errorprone_error_prone_check_api",
    ],
)

java_library(
    name = "auto_service",
    exported_plugins = [
        ":auto_service_plugin",
    ],
    exports = [
        "@maven//:com_google_auto_service_auto_service_annotations",
    ],
)

java_plugin(
    name = "auto_service_plugin",
    processor_class = "com.google.auto.service.processor.AutoServiceProcessor",
    deps = [
        "@maven//:com_google_auto_service_auto_service",
    ],
)

Starting in version 3.5, maven-compiler-plugin allows the processor path to be configured with the annotationProcessorPaths parameter.

Plugin checkers can accept additional configuration flags by defining a single-argument constructor taking an ErrorProneFlags object (see the flags docs). However, note that plugin checkers must also define a zero-argument constructor, as they are loaded by a ServiceLoader. The actual checker instance used by Error Prone will be constructed using the ErrorProneFlags constructor.