go_package paths in proto files not supported

[rutsky]

I'm trying to generate build rules with Gazelle for a project that uses interdependent proto files and include them by package name, but Gazelle/rules_go fails in multiple ways.

I prepared small example to reproduce the issue: https://github.com/rutsky/gazelle_proto_import

├── BUILD
├── hello_proto
│   ├── BUILD.bazel
│   └── hello.proto
├── server_proto
│   ├── BUILD.bazel
│   └── server.proto
└── WORKSPACE

server.proto:

syntax = "proto3";

package server;

import "github.com/rutsky/gazelle_proto_import/hello_proto/hello.proto";

option go_package = "github.com/rutsky/gazelle_proto_import/server_proto;server"; 

service Greeter {
  rpc SayHello (hello.HelloRequest) returns (hello.HelloReply) {}
}

hello.proto:

syntax = "proto3";

package hello;

option go_package = "github.com/rutsky/gazelle_proto_import/hello_proto;hello"; 

message HelloRequest {
  string name = 1;
}

message HelloReply {
  string message = 1;
}

server.proto depends on hello.proto by using absolute package import path.

There are following issues.

1. When I run bazel run //:gazelle, server_proto rule for server.proto gets deps = ["//github.com/rutsky/gazelle_proto_import/hello_proto:hello_proto_proto"], which clearly doesn't exists and build fails.

   I can fix this by manually setting proper path to dependency (e.g. rutsky/gazelle_proto_import@7c45b8d).

2. With fixed dependency this still won't build, as bazel is not informed of what are those absolute packages names:

$ bazel build -s //server_proto
INFO: Analysed target //server_proto:server_proto (0 packages loaded).
INFO: Found 1 target...
SUBCOMMAND: # //server_proto:server_proto [action 'Generating Descriptor Set proto_library //server_proto:server_proto']
(cd /home/bob/.cache/bazel/_bazel_bob/b5a692e6e2b62f927f1e063c9b530723/execroot/gazelle_proto_import && \
  exec env - \
    LD_LIBRARY_PATH=/home/bob/.local/lib:/home/bob/.local/lib: \
    PATH=/home/bob/.local/share/umake/bin:/home/bob/bin:/home/bob/stuff/go//bin:/home/bob/bin:/home/bob/.nvm/versions/node/v6.4.0/bin:/home/bob/.local/bin:/home/bob/.gem/ruby/2.2.0/bin:/home/bob/bin:/home/bob/stuff/go//bin:/home/bob/bin:/home/bob/.local/bin:/home/bob/.gem/ruby/2.2.0/bin:/home/bob/bin:/home/bob/.local/share/umake/bin:/home/bob/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/mnt/media/bob/Android/Sdk/tools:/mnt/media/bob/Android/Sdk/platform-tools:/mnt/media/bob/Android/Sdk/tools:/mnt/media/bob/Android/Sdk/platform-tools \
  bazel-out/host/bin/external/com_google_protobuf/protoc '--descriptor_set_out=bazel-out/k8-fastbuild/genfiles/server_proto/server_proto-descriptor-set.proto.bin' '-Iserver_proto/server.proto=server_proto/server.proto' '-Ihello_proto/hello.proto=hello_proto/hello.proto' --direct_dependencies hello_proto/hello.proto:server_proto/server.proto '--direct_dependencies_violation_msg=%s is imported, but //server_proto:server_proto doesn'\''t directly depend on a proto_library that '\''srcs'\'' it.' server_proto/server.proto)
ERROR: /home/bob/stuff/go/src/github.com/rutsky/gazelle_proto_import/server_proto/BUILD.bazel:4:1: Generating Descriptor Set proto_library //server_proto:server_proto failed (Exit 1)
github.com/rutsky/gazelle_proto_import/hello_proto/hello.proto: File not found.
server_proto/server.proto: Import "github.com/rutsky/gazelle_proto_import/hello_proto/hello.proto" was not found or had errors.
server_proto/server.proto:10:17: "hello.HelloRequest" is not defined.
server_proto/server.proto:10:46: "hello.HelloReply" is not defined.
Target //server_proto:server_proto failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 0.306s, Critical Path: 0.06s
INFO: 0 processes.
FAILED: Build did NOT complete successfully

I expected that something similar by effect to this command would be generated:

protoc --go_out=plugins=grpc:. \
  -Igithub.com/rutsky/gazelle_proto_import/hello_proto/hello.proto=hello_proto/hello.proto \
  -Igithub.com/rutsky/gazelle_proto_import/hello_proto/server.proto=server_proto/server.proto \
  server_proto/server.proto 

I assume go_package paths should be supported by Gazelle (according to this comment they work and).
I saw that absolute includes work with some grpc/gogo built-ins (like import "google/protobuf/empty.proto";), though it seems this is hardcoded inside rules_go.

It seems this should be possible to implement at least as this was done for gogo support in rules_go (https://github.com/bazelbuild/rules_go/blob/8b0118fff2ea415c93f02670bd8fde5aa76d3404/proto/gogo.bzl#L34), though it seems too low level and overkill.

[jayconrod]

I think you're running into a limitation in Bazel: bazelbuild/bazel#3867.

The proto_library rule (native to Bazel) is what runs protoc. It expects imports to be relative to the workspace root directory, either in a local workspace or in an external workspace. So you would need to write import hello_proto/hello.proto. There is no way that I know of to set the import directories.

If you can't update your .proto files (e.g., because some of them are vendored), I'd suggest pre-generating your .pb.go files outside of Bazel, and adding # gazelle:proto disable_global in your root build file to avoid generating proto_library and go_proto_library rules.

[jayconrod]

Closing this because there's nothing Gazelle can do at the moment. When Bazel can build proto_library rules with imports like this, I'll update Gazelle to generate those rules.