protoc-gen-go-template

protoc-gen-go-template

protoc-gen-go-template is a protocol guffer generator using go templates applied to .proto file descriptors as defined in descriptor.proto

Install

Install protoc and go get github.com/jrmarkle/protoc-gen-go-template. $(go env GOPATH)/bin must be in your PATH.

Example

Suppose you have the file example.proto from which you want to generate custom code:

syntax = "proto3";
package example;
option go_package = "example";

enum MyEnum {
	foo = 0;
	bar = 1;
	baz = 2;
}

Using this template file enums.tmpl:

{{ if .EnumType }}
package {{ .Package }}

import "github.com/golang/protobuf/proto"

{{ range .EnumType }}

func (m {{ .Name }}) Enum() *{{ .Name }} {
	p := new({{ .Name }})
	*p = m
	return p
}

func (m *{{ .Name }}) UnmarshalJSON(data []byte) error {
	value, err := proto.UnmarshalJSONEnum({{ .Name }}_value, data, "{{ .Name }}")
	if err != nil {
		return err
	}
	*m = {{ .Name }}(value)
	return nil
}
{{ end }}
{{ end }}

Run protoc --go-template_out=enums.tmpl,format:. example.proto to generate example.pb.enums.go:

package example

import "github.com/golang/protobuf/proto"

func (m MyEnum) Enum() *MyEnum {
	p := new(MyEnum)
	*p = m
	return p
}

func (m *MyEnum) UnmarshalJSON(data []byte) error {
	value, err := proto.UnmarshalJSONEnum(MyEnum_value, data, "MyEnum")
	if err != nil {
		return err
	}
	*m = MyEnum(value)
	return nil
}

You can use this example as a workaround for protobuf issue #256.

Parameters

The paramters must be a comma-separated list. (In the above example, the parameters are enums.tmpl,format.) At least one parameter must be the name of your template file. If multiple files are listed, only the first will be used. You may omit the .tmpl extension from the parameter and/or the file name itself if you prefer.

Use the format parameter to have the output formatted with gofmt style. Don't use this paramter if you aren't generating go code.