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GopherJS support for Protocol Buffers and gRPC-Web

Generate GopherJS interfaces to ProtobufJS and gRPC Web from your proto files.

Attribution

Most of the code is based on a fork of Googles protoc-gen-go code generator, with heavy modifications to output GopherJS compatible structs.

Compatibility

Only proto files with syntax="proto3"; are supported.

Installation

To use this software, you must:

  1. Install the protocol buffer compiler, protoc: https://developers.google.com/protocol-buffers/

  2. Install the Go compiler and tools: https://golang.org/

  3. Grab the code from the repository and install the proto package.

    $ go get -u github.com/johanbrandhorst/protobuf/protoc-gen-gopherjs

    The compiler plugin, protoc-gen-gopherjs, will be installed in $GOBIN, defaulting to $GOPATH/bin. It must be in your $PATH for the protocol compiler, protoc, to find it.

This package generates files that import the GopherJS ProtobufJS bindings. The generated interface is designed to be as similar as possible to that of files generated with protoc-gen-go, with one exception:

  • Marshal and Unmarshal methods for each type. Instead of proto.Marshal and proto.Unmarshal, these are used to serialize to and from binary.

Usage

Once the software is installed, there are two steps to using it. First you must compile the protocol buffer definitions and then import them into your program.

To compile the protocol buffer definition, run protoc with the --gopherjs_out parameter set to the directory you want to output the GopherJS code to.

 $ protoc --gopherjs_out=.  *.proto

The generated files are suffixed .pb.gopherjs.go.

An example

Consider the file test.proto, containing

syntax="proto3";

package example;

message Test {
	string label = 1;
	int32 type = 2;
	int64 reps = 3;
}

Generate it:

$ protoc --gopherjs_out=. test.proto

This generates the following client code (abbreviated):

// Code generated by protoc-gen-gopherjs. DO NOT EDIT.
// source: test.proto

package example

import jspb "github.com/johanbrandhorst/protobuf/jspb"

type Test struct {
	Label string
	Type  int32
	Reps  int64
}

// Getters...

// MarshalToWriter marshals Test to the provided writer.
func (m *Test) MarshalToWriter(writer jspb.Writer) {
	if m == nil {
		return
	}
	if len(m.Label) > 0 {
		writer.WriteString(1, m.Label)
	}
	if m.Type != 0 {
		writer.WriteInt32(2, m.Type)
	}
	if m.Reps != 0 {
		writer.WriteInt64(3, m.Reps)
	}
}

// Marshal marshals Test to a slice of bytes.
func (m *Test) Marshal() []byte {
	writer := jspb.NewWriter()
	m.MarshalToWriter(writer)
	return writer.GetResult()
}

// UnmarshalFromReader unmarshals a Test from the provided reader.
func (m *Test) UnmarshalFromReader(reader jspb.Reader) *Test {
	for reader.Next() {
		if m == nil {
			m = &Test{}
		}

		switch reader.GetFieldNumber() {
		case 1:
			m.Label = reader.ReadString()
		case 2:
			m.Type = reader.ReadInt32()
		case 3:
			m.Reps = reader.ReadInt64()
		default:
			reader.SkipField()
		}
	}

	return m
}

// Unmarshal unmarshals a Test from a slice of bytes.
func (m *Test) Unmarshal(rawBytes []byte) (*Test, error) {
	reader := jspb.NewReader(rawBytes)

	m = m.UnmarshalFromReader(reader)

	if err := reader.Err(); err != nil {
		return nil, err
	}

	return m, nil
}

In your client code, you can use the library like so:

package main

import "github.com/youruser/yourrepo/example"

func main() {
	t := example.Test{
		Label: "Label",
		Type: 1234,
		Rep: 5678,
	}
	rawBytes, err := t.Marshal()
	if err != nil {
		panic(err)
	}

	t1, err := new(example.Test).Unmarshal(rawBytes)
	if err != nil {
		panic(err)
	}
}

Parameters

To pass extra parameters to the plugin, use a comma-separated parameter list separated from the output directory by a colon:

$ protoc --gopherjs_out=plugins=grpc,import_path=mypackage:. *.proto
1. `import_prefix=xxx` - a prefix that is added onto the beginning of

all imports. Useful for things like generating protos in a subdirectory, or regenerating vendored protobufs in-place. 1. import_path=foo/bar - used as the package if no input files declare gopherjs_package. If it contains slashes, everything up to the rightmost slash is ignored. 1. plugins=plugin1+plugin2 - specifies the list of sub-plugins to load. The only plugin in this repo is grpc. 1. Mfoo/bar.proto=quux/shme - declares that foo/bar.proto is associated with Go package quux/shme. This is subject to the import_prefix parameter.

Generate gRPC-Web/WsProxy bindings

If a proto file specifies RPC services, protoc-gen-gopherjs can be instructed to generate code compatible with the GopherJS gRPC-Web bindings. To do this, pass the plugins parameter to protoc-gen-gopherjs:

$ protoc --gopherjs_out=plugins=grpc:. *.proto

Use of the gRPC-Web/WsProxy bindings require the target gRPC server to be wrapped by the Improbable gRPC-Web proxy and the gRPC-Web Websocket proxy. See the test setup for an example implementation of this wrapping.