Avoid passing both the short and the long proto paths to protoc

[iirina]

Currently for each .proto file Bazel passes to protoc the path relative to the workspace (the long path) via -I flag (alias for --proto_path).

Since 15a4362, Bazel also passes to protoc a short path via the --proto_path flag. The short path is only passed for proto_library targets that have set proto_source_root.

Passing to protoc both the short and the long path to a .proto file is error prone. A better mechanism must be implemented to deal with these situations.

[iirina]

More context in bazelbuild/bazel#4544.

[wjywbs]

Ping for this bug.

I'm importing protobuf code to //third_party/protobuf, but the proto_library rule [1] fails to build. Adding proto_source_root="third_party/protobuf" doesn't fix the build. The failing command is:

bazel-out/host/bin/third_party/protobuf/protoc '--proto_path=third_party/protobuf' '--descriptor_set_out=bazel-out/k8-opt/genfiles/third_party/protobuf/type_proto-descriptor-set.proto.bin' '-Ithird_party/protobuf/google/protobuf/type.proto=bazel-out/k8-opt/genfiles/third_party/protobuf/google/protobuf/type.proto' '-Ithird_party/protobuf/google/protobuf/any.proto=bazel-out/k8-opt/genfiles/third_party/protobuf/google/protobuf/any.proto' '-Ithird_party/protobuf/google/protobuf/source_context.proto=bazel-out/k8-opt/genfiles/third_party/protobuf/google/protobuf/source_context.proto' --direct_dependencies third_party/protobuf/google/protobuf/any.proto:third_party/protobuf/google/protobuf/source_context.proto:third_party/protobuf/google/protobuf/type.proto bazel-out/k8-opt/genfiles/third_party/protobuf/google/protobuf/type.proto

Generating Descriptor Set proto_library //third_party/protobuf:type_proto failed (Exit 1).
third_party/protobuf: warning: directory does not exist.
google/protobuf/any.proto: File not found.
google/protobuf/source_context.proto: File not found.
third_party/protobuf/google/protobuf/type.proto: Import "google/protobuf/any.proto" was not found or had errors.
third_party/protobuf/google/protobuf/type.proto: Import "google/protobuf/source_context.proto" was not found or had errors.
third_party/protobuf/google/protobuf/type.proto:57:3: "SourceContext" is not defined.
third_party/protobuf/google/protobuf/type.proto:151:3: "SourceContext" is not defined.
third_party/protobuf/google/protobuf/type.proto:178:3: "Any" is not defined.

I think the -Ithird_party/protobuf/google/protobuf/type.proto etc should be -Igoogle/protobuf/type.proto. And --direct_dependencies also needs to strip third_party/protobuf/.

The command below works with or without --proto_path=third_party/protobuf.

bazel-out/host/bin/third_party/protobuf/protoc '--proto_path=third_party/protobuf' '--descriptor_set_out=bazel-out/k8-opt/genfiles/third_party/protobuf/type_proto-descriptor-set.proto.bin' '-Igoogle/protobuf/type.proto=bazel-out/k8-opt/genfiles/third_party/protobuf/google/protobuf/type.proto' '-Igoogle/protobuf/any.proto=bazel-out/k8-opt/genfiles/third_party/protobuf/google/protobuf/any.proto' '-Igoogle/protobuf/source_context.proto=bazel-out/k8-opt/genfiles/third_party/protobuf/google/protobuf/source_context.proto' --direct_dependencies google/protobuf/any.proto:google/protobuf/source_context.proto:protobuf/google/protobuf/type.proto bazel-out/k8-opt/genfiles/third_party/protobuf/google/protobuf/type.proto

[1] https://github.com/protocolbuffers/protobuf/blob/master/BUILD#L264

[iirina]

Changed to P3 because I'm not planning to work on this next quarter.

[Yannic]

A lot has changed since 2018 (e.g. the aforementioned proto_source_root has since been removed), so I'm not sure if this is still an issue.

There's also work going on to change how .proto files are compiled (e.g. bazelbuild/bazel#10939, bazelbuild/bazel#1005), which will definitely fix this (in case it isn't already fixed).

[Yannic]

Fixed in bazelbuild/bazel#10939