Incompatibility with rules_java 8.12.0

[rafikk]

Hello! I’m testing my repo against rules_java 8.12.0 with rules_scala 7.0.0, and running into the following build error on scala_specs2_junit_test targets:

Traceback (most recent call last):
	File "/private/var/tmp/_bazel_rafiksalama/1d5a93ad130d5a2bb2604b5c76cd5ad7/external/rules_java+/java/bazel/rules/bazel_java_import.bzl", line 25, column 34, in _proxy
		return bazel_java_import_rule(
	File "/private/var/tmp/_bazel_rafiksalama/1d5a93ad130d5a2bb2604b5c76cd5ad7/external/rules_java+/java/common/rules/impl/bazel_java_import_impl.bzl", line 129, column 28, in bazel_java_import_rule
		_check_empty_jars_error(ctx, jars)
	File "/private/var/tmp/_bazel_rafiksalama/1d5a93ad130d5a2bb2604b5c76cd5ad7/external/rules_java+/java/common/rules/impl/bazel_java_import_impl.bzl", line 75, column 13, in _check_empty_jars_error
		fail("empty java_import.jars is not supported " + ctx.label.package)
Error in fail: empty java_import.jars is not supported specs2

The @rules_scala//specs2:specs2 target indeed specifies an empty jars attribute. Adding --noincompatible_disallow_java_import_empty_jars to bazelrc doesn’t seem to help, so this appears to be a hard incompatibility.

cc @mbland

[mbland]

Other relevant information provided by @rafikk from the original #scala thread in the Bazel Slack workspace:

--noincompatible_disallow_java_import_empty_jars actually doesn't help, and the change in rules_java calls this out. so it looks like this is a hard incompatibity between latest rules_java and rules_scala 7.0.0

I think I have an idea how to fix this, and I was planning to open a pull request to bump versions anyway. Feel free to assign this to me.