Public import is not included in generated CommonJS file

System

Version: v3.6.1
Language: Javascript
macOS 10.14

Steps to reproduce

1. Create a src directory with 3 files:

   // id.proto
   syntax = "proto3";
   
   message Id {
     string value = 1;
   }
   

   // task.proto adding a transitive import for `Id`
   syntax = "proto3";
   import public "id.proto";
   
   message Task {
     Id id = 1;
   }
   

   // project.proto importing both `Id` and `Task` from Project
   syntax = "proto3";
   import "task.proto";
   
   message Project {
     Id id = 1;
     repeated Task task = 2;
   }
   

2. Compile to js using

   mkdir build
   protoc --proto_path=src --js_out=import_style=commonjs,binary:build id.proto task.proto project.proto 
   

3. npm install google-protobuf under the root directory.
4. node test.js

   // test.js
   var id_pb = require('./build/id_pb');
   var project_pb = require('./build/project_pb');
   
   var id = new id_pb.Id();
   id.setValue("Everything is fine");
   
   var project = new project_pb.Project()
   project.setId(id);
   
   process.stdout.write(project.getId().getValue());
   process.stdout.write("\n");
   

Expected behaviour

Everything is fine is printed to the console.

Actual behaviour

.../test-proto/build/project_pb.js:173
    jspb.Message.getWrapperField(this, id_pb.Id, 1));
                                       ^

ReferenceError: id_pb is not defined
    at proto.Project.getId (.../test-proto/build/project_pb.js:173:40)
    at Object.<anonymous> (.../test-proto/test.js:10:30)
    at Module._compile (internal/modules/cjs/loader.js:688:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:699:10)
    at Module.load (internal/modules/cjs/loader.js:598:32)
    at tryModuleLoad (internal/modules/cjs/loader.js:537:12)
    at Function.Module._load (internal/modules/cjs/loader.js:529:3)
    at Function.Module.runMain (internal/modules/cjs/loader.js:741:12)
    at startup (internal/bootstrap/node.js:285:19)
    at bootstrapNodeJSCore (internal/bootstrap/node.js:739:3)

id_pb import is missing from project_pb. Alternatively it may be referenced from task_pb, since it’s declared public in task.proto.

The error does not show up if id.proto is explicitly imported in project.proto.

Reproduce the case with the provided protoc command, then inspect build/project_pb.js and the generated imports for id_pb and task_pb. Use test.js to verify the behavior; done means the transitive public import is available to project_pb.js and the script prints “Everything is fine” without requiring an explicit import in project.proto.