[bazel] Fix blacklisted_protos in cc_toolchain and add test

[Yannic]

No description provided.

[Yannic]

We're running the test that verifies WKPs are excluded twice: One time as //:cc_proto_blacklist_test and one time as @com_google_protobuf//:cc_proto_blacklist_test. For some reason, it passes only one time. I have no idea why that makes a difference.

I see the same errors for Bazel 2.0.0 and Bazel 2.0.0 + bazelbuild/bazel#10493

$ /private/var/tmp/_bazel_yannic/1460a25073e849a4f43b8278b99f9b6d/execroot/io_bazel/bazel-out/darwin-fastbuild/bin/src/bazel test @com_google_protobuf//:cc_proto_blacklist_test //:cc_proto_blacklist_test
INFO: Invocation ID: 811f4b86-e0c0-4580-b7ff-b98f5533e30a
DEBUG: /private/var/tmp/_bazel_yannic/c28f18b452d490f3ae8554a2bc9b8bed/external/bazel_skylib/lib/unittest.bzl:351:5: In test _cc_proto_blacklist_test_impl from //:cc_proto_blacklist_test.bzl: Expected "0", but got "48"
INFO: Analyzed 2 targets (0 packages loaded, 0 targets configured).
INFO: Found 2 test targets...
FAIL: //:cc_proto_blacklist_test (see /private/var/tmp/_bazel_yannic/c28f18b452d490f3ae8554a2bc9b8bed/execroot/com_google_protobuf/bazel-out/darwin-fastbuild/testlogs/cc_proto_blacklist_test/test.log)
INFO: Elapsed time: 0.705s, Critical Path: 0.49s
INFO: 2 processes: 2 darwin-sandbox.
INFO: Build completed, 1 test FAILED, 2 total actions
@com_google_protobuf//:cc_proto_blacklist_test                  (cached) PASSED in 0.1s
//:cc_proto_blacklist_test                                               FAILED in 0.3s
  /private/var/tmp/_bazel_yannic/c28f18b452d490f3ae8554a2bc9b8bed/execroot/com_google_protobuf/bazel-out/darwin-fastbuild/testlogs/cc_proto_blacklist_test/test.log

Executed 1 out of 2 tests: 1 test passes and 1 fails locally.
INFO: Build completed, 1 test FAILED, 2 total actions

Currently bisecting if that ever worked...

[Yannic]

I tried several Bazel versions between 0.20.0 and 2.0.0, but I always see the behavior from my previous comment.

[jtattermusch]

I tried several Bazel versions between 0.20.0 and 2.0.0, but I always see the behavior from my previous comment.

Any progress on this?

[Yannic]

Unfortunately not, but IIUC, the failing test only indicates that blacklisting doesn't work inside the protobuf repo, anyone else should be fine (see grpc/grpc#21590 (comment)).

However, running the test on 3.8 with the old blacklisting mechanism also fails with the same error, so I think this (and #7096) can be merged.

[Yannic]

bazel test @com_google_protobuf//:cc_proto_blacklist_test //:cc_proto_blacklist_test does show a bug in how Bazel handles the blacklist (bazelbuild/bazel#10590).

When using the default toolchain for cc_proto_library (--proto_toolchain_for_cc=@com_google_protobuf//:cc_toolchain), @com_google_protobuf//:cc_proto_blacklist_test passes and //:cc_proto_blacklist_test fails.
When changing the toolchain to --proto_toolchain_for_cc=//:cc_toolchain, //:cc_proto_blacklist_test starts passing and @com_google_protobuf//:cc_proto_blacklist_test fails.

This is only an issue for the protobuf repo itself, everyone else is fine.