Support for passing extra compiler options

[bsravanin]

Would it be possible to support passing additional compiler options to java_proto_library like in https://docs.bazel.build/versions/master/be/java.html#java_library_args

We find it useful to pass Error-Prone's -XepDisableAllChecks while generating Java code for protos, but haven't figured out how since switching to rules_java.

[dwtj]

Is the javacopts attribute what you're looking for? Looks like it is present on the java_library, java_binary and java_test rules.

E.g.

java_library(
    name = "foo",
    srcs = [...],
    javacopts = ["-XepDisableAllChecks"],
)

[jfancher]

The question is specifically about java_proto_library, which unfortunately does not have a javacopts attr (perhaps the title should be clarified). Supporting javacopts on that rule would provide a solution -- although perhaps not an ideal one, as you'd have to wrap it in a macro to apply to all libs.

We have a few large proto files that are expensive (>10s) to build, and running errorprone increases the compilation time by about 50%. We expect errorprone to be pointless for such generated code, as well, so this extra time is entirely wasted.

I did find a workaround by digging through Bazel internals: java_toolchain has a hidden attr compatible_javacopts you can use like this:

java_toolchain(
  name = "toolchain_java8",
  compatible_javacopts = {
    "proto": ["-XepDisableAllChecks"],
  },
  ...
}

This seems to do exactly what we want, so it'll do for now.

However, it'd obviously be preferable to have an officially-supported way to do this rather than relying on an internal flag.

[comius]

I believe the response in #3427 (comment) should be the preferred way to do this and that it supports your usecase.

[jfancher]

Unless I am misunderstanding, I don't believe that option would work for us without substantial reorganization unfortunately. We do not put protobuf libraries in separate Bazel packages; they exist side-by-side with code, so package-level configuration wouldn't be sufficient.

[guw]

Echoing the need for a way to allow customization of javac options on java_proto_library. Specifically because the generated code causes compile errors/warnings, which we would like to ignore.

We use java_package_configuration to set workspace wide defaults which are more strict. Adding excludes to the package_group used by java_package_configuration is not possible because it doesn't allow to exclude specific targets. It operates at the package level. Thus, it's required to do this at the java_proto_library level where it's needed.