Protobuf Transpiler

A protobuf transpiler and annotator for Rails applications.

This gem provides a quick way to generate annotated ruby stubs for protobufs leveraging Ruby gRPC Tools, adopting an opinionated Rails oriented approach.

Add this line to your application's Gemfile:

gem 'protobuf_transpiler', '~> 1.0'

And then execute:

bundle

This gem provides two rake tasks, grpc_stubs:generate and grpc_stubs:annotate. generate transpiles all .proto files nested in a public folder looking in the $LOAD_PATH, putting the generated ruby stubs in app/stubs, respecting the inner nesting. annotate annotates all the generated stubs with a comment section leveraging reflection.

Beware that at the moment this gem does not support nested messages definition.

To generate the stubs simply run:

rake grpc_stubs:generate

The task accepts two optional positional arguments, annotate and keep_require which default respectively to 'yes' and 'no'. This means that by default the generate task also runs the annotate one, and the behavior can be changed by specifying the first argument as 'no'. Furthermore the default behavior of generate removes all the require ... generated by grpc_tools_ruby_protoc; if, for any reason, you may want to keep them, you need to specify the second argument as 'yes' (which implies you need to explicitly state the first parameter, even if you want to keep the default behavior). Finally, following the stubs generation, the task also creates a ruby file for all the proto packages, which corresponds to the created folders in app/stubs, containing require_relative instructions to the corresponding stubs. This allows zeitwerk to work properly despite grpc_tools_ruby_protoc not respecting the naming conventions.

For example if you have a gem defining proto files with this structure:

 public
 ├── mod1
 │   └── sample1.proto
 ├── mod2
 │   └── sample2.proto

you will get the following structure nested in app/stubs:

app/stubs
├── mod1
│   ├── sample1_pb.rb
│   └── sample1_services_pb.rb
├── mod1.rb
├── mod2
│   ├── sample2_pb.rb
│   └── sample2_services_pb.rb
├── mod2.rb

To annotate generated stubs simply run:

rake grpc_stubs:annotate

As stated in generate this task is executed automatically unless you opt out after the generation step. Leveraging reflection, Messages and Services are inspected and a comment summary is prepended in the corresponding stub file.

The annotations of messages follow these conventions:

• each message is reported with its fully qualified name
• fields are indented in the lines following the message name and are reported as name: type
• repeated fields are annotated with their type enclosed in brackets ([type])
• map fields are annotated with angular brackets: Map<key_type, value_type>
• oneof fields are annotated with their wrapper name, then each possible variant placed on a new line, further indented and prepended with | .

Here's an example of annotations of some messages:

# ===== Protobuf Annotation =====
# Test::GetJobReq
# 	id: uint64
#   some_oneof_wrapper:
# 	  | alternative: string
# 	  | another: uint64
# Test::GetJobResp
# 	id: uint64
# 	name: string
# 	surname: string
#   notes: [string]
# ===== Protobuf Annotation =====

and some rpcs:

# ===== Protobuf Annotation =====
# Test::Jobs
# 	GetJob(Test::GetJobReq): Test::GetJobResp
# Test::Another
# 	GetNew(Test::GetJobReq): Test::GetJobResp
# ===== Protobuf Annotation =====

• Support nested messages definition

Protobuf Transpiler loosely follows Semantic Versioning, with a hard guarantee that breaking changes to the public API will always coincide with an increase to the MAJOR number.

Version numbers are in three parts: MAJOR.MINOR.PATCH.

• Breaking changes to the public API increment the MAJOR. There may also be changes that would otherwise increase the MINOR or the PATCH.
• Additions, deprecations, and "big" non breaking changes to the public API increment the MINOR. There may also be changes that would otherwise increase the PATCH.
• Bug fixes and "small" non breaking changes to the public API increment the PATCH.

Notice that any feature deprecated by a minor release can be expected to be removed by the next major release.

Full list of changes in CHANGELOG.md

Bug reports and pull requests are welcome on GitHub at https://github.com/moku-io/protobuf_transpiler.

The gem is available as open source under the terms of the MIT License.