protobuf.generate is a mix task that allows you to generate Elixir code using Protobuf without using the protoc-gen-elixir plugin.

The generator calls protoc using descriptor_set_out to output a FileDescriptorSet into a temporary file for input to Protobuf.

The difference between protobuf.generate and protoc-gen-elixir is that protoc-gen-elixir is called as a plugin to protoc and therefor executes in a global context while protobuf.generate executes in the context of the local project.

By executing in the context of the local project:

• Extensions that needs to be populated during code generation are picked up automatically by Protobuf.load_extensions/0 (which is not possible when using protoc-gen-elixir).

• Integration into the codegen by using generator plugins. See ProtobufGenerate.Plugin

• Protoc (protocol buffer compiler) is required to be installed. Download and install the protocol buffer compiler (protoc).

This package can be installed by adding protobuf_generate to your list of dependencies in mix.exs:

def deps do
  [
    {:protobuf_generate, "~> 0.1.0"}
  ]
end

mix protobuf.generate supports the same options as protoc-gen-elixir

• file - One or more .proto files to compile

• --output-path - Path to output directory

• --include-path - Specify the directory in which to search for imports. Eqvivalent to protoc -I flag.

• --tranform-module - Module to do custom encoding/decoding for messages. See Protobuf.TransformModule for details.

• --package-prefix - Prefix generated Elixir modules. For example prefix modules with: MyApp.Protos use --package-prefix=my_app.protos.

• --generate-descriptors - Includes raw descriptors in the generated modules

• --one-file-per-module - Changes the way files are generated into directories. This option creates a file for each generated Elixir module.

• --include-documentation - Controls visibility of documentation of the generated modules. Setting true will not have @moduleoc false

• --plugins - Generator plugins. If you write services in protobuf, you can generate gRPC code by passing --plugins=ProtobufGenerate.Plugins.GRPC.

$ mix protobuf.generate --output-path=./lib --include-path=./priv/protos helloworld.proto
$ mix protobuf.generate \
  --include-path=priv/proto \
  --include-path=deps/googleapis \
  --generate-descriptors=true \
  --output-path=./lib \
  --plugins=ProtobufGenerate.Plugins.GRPCWithOptions \
  google/api/annotations.proto google/api/http.proto helloworld.proto

• ProtobufGenerate.Plugins.GRPC - Generate gRPC services
• ProtobufGenerate.Plugins.GRPCWithOptions - Generate gRPC services with method extension options.

Extensions in the current project are loaded automatically when running mix protobuf.generate. However they need to be already generated in order for Protobuf.load_extensions/0 to pick them up.

• protox for running protoc with descriptor_set_out