protoc-gen-go-tag

README

protoc-gen-go-tag

Generates Go code using a package as a tag rewriter that enhanced protoc-gen-go.

protoc-gen-go-tag Generates Go code using a package as a tag rewriter that enhanced protoc-gen-go.

The file xxx.pb.go is modified by protoc-gen-go based on xxx.proto. It has helpful defaults designed for use with protobuf with custom struct tags.

For example, given this snippet,

apply this proto file

syntax = "proto3";

package pb;

//import "google/protobuf/descriptor.proto";
import "github.com/searKing/golang/tools/protoc-gen-go-tag/tag/tag.proto";

message Http{
  string protocol = 1;
  string version = 2[json_name = "Url", (google.protobuf.field_tag) = {struct_tag: "validate:\"gte=0,lte=130\""}];;
  Url url = 3[json_name = "Url", (google.protobuf.field_tag) = {struct_tag: "json:\"url_tag,omitempty\""}];
  message Url {
    string scheme = 1[json_name = "Scheme", (google.protobuf.field_tag) = {struct_tag: "json:\"schema_tag,omitempty\""}];
    //  string scheme = 1[json_name = "Scheme"];
  }
}

running this command

# https://github.com/searKing/golang/blob/master/tools/protoc-gen-go-tag/tag/tag.proto
# `tag.proto` needs to be on the `protoc` include path 
protoc -I . --go-tag_out=paths=source_relative:. *.proto

in the same directory will create the file pill.pb.go, containing

// Code generated by protoc-gen-go-tag. DO NOT EDIT.
// Code generated by protoc-gen-go. DO NOT EDIT.
// versions:
// 	protoc-gen-go v1.27.1
// 	protoc        v3.17.3
// source: example.proto

package pb

import (
  _ "github.com/searKing/golang/tools/protoc-gen-go-tag/tag"
  protoreflect "google.golang.org/protobuf/reflect/protoreflect"
  protoimpl "google.golang.org/protobuf/runtime/protoimpl"
  reflect "reflect"
  sync "sync"
)

const (
  // Verify that this generated code is sufficiently up-to-date.
  _ = protoimpl.EnforceVersion(20 - protoimpl.MinVersion)
  // Verify that runtime/protoimpl is sufficiently up-to-date.
  _ = protoimpl.EnforceVersion(protoimpl.MaxVersion - 20)
)

type Http struct {
  state         protoimpl.MessageState
  sizeCache     protoimpl.SizeCache
  unknownFields protoimpl.UnknownFields

  Protocol string `protobuf:"bytes,1,opt,name=protocol,proto3" json:"protocol,omitempty" validate:"oneof=http https"`
  // version_default is the same as version_update
  VersionDefault string    `protobuf:"bytes,2,opt,name=version_default,json=VersionDefault,proto3" json:"version_with_default,omitempty" validate:"gte=0,lte=130"`
  VersionUpdate  string    `protobuf:"bytes,3,opt,name=version_update,json=VersionUpdate,proto3" json:"version_with_update,omitempty" validate:"gte=0,lte=130"`
  VersionReplace string    `protobuf:"bytes,4,opt,name=version_replace,json=VersionReplace,proto3" json:"version_with_replace" validate:"gte=0,lte=130"`
  Url            *Http_Url `protobuf:"bytes,5,opt,name=url,json=Url,proto3" json:"url_tag,omitempty"`
}

func (x *Http) Reset() {
  *x = Http{}
  if protoimpl.UnsafeEnabled {
    mi := &file_example_proto_msgTypes[0]
    ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
    ms.StoreMessageInfo(mi)
  }
}

func (x *Http) String() string {
  return protoimpl.X.MessageStringOf(x)
}

func (*Http) ProtoMessage() {}

func (x *Http) ProtoReflect() protoreflect.Message {
  mi := &file_example_proto_msgTypes[0]
  if protoimpl.UnsafeEnabled && x != nil {
    ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
    if ms.LoadMessageInfo() == nil {
      ms.StoreMessageInfo(mi)
    }
    return ms
  }
  return mi.MessageOf(x)
}

// Deprecated: Use Http.ProtoReflect.Descriptor instead.
func (*Http) Descriptor() ([]byte, []int) {
  return file_example_proto_rawDescGZIP(), []int{0}
}

func (x *Http) GetProtocol() string {
  if x != nil {
    return x.Protocol
  }
  return ""
}

func (x *Http) GetVersionDefault() string {
  if x != nil {
    return x.VersionDefault
  }
  return ""
}

func (x *Http) GetVersionUpdate() string {
  if x != nil {
    return x.VersionUpdate
  }
  return ""
}

func (x *Http) GetVersionReplace() string {
  if x != nil {
    return x.VersionReplace
  }
  return ""
}

func (x *Http) GetUrl() *Http_Url {
  if x != nil {
    return x.Url
  }
  return nil
}

type Http_Url struct {
  state         protoimpl.MessageState
  sizeCache     protoimpl.SizeCache
  unknownFields protoimpl.UnknownFields

  Scheme string `protobuf:"bytes,1,opt,name=scheme,json=Scheme,proto3" json:"schema_tag,omitempty"` //  string scheme = 1[json_name = "Scheme"];
}

func (x *Http_Url) Reset() {
  *x = Http_Url{}
  if protoimpl.UnsafeEnabled {
    mi := &file_example_proto_msgTypes[1]
    ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
    ms.StoreMessageInfo(mi)
  }
}

func (x *Http_Url) String() string {
  return protoimpl.X.MessageStringOf(x)
}

func (*Http_Url) ProtoMessage() {}

func (x *Http_Url) ProtoReflect() protoreflect.Message {
  mi := &file_example_proto_msgTypes[1]
  if protoimpl.UnsafeEnabled && x != nil {
    ms := protoimpl.X.MessageStateOf(protoimpl.Pointer(x))
    if ms.LoadMessageInfo() == nil {
      ms.StoreMessageInfo(mi)
    }
    return ms
  }
  return mi.MessageOf(x)
}

// Deprecated: Use Http_Url.ProtoReflect.Descriptor instead.
func (*Http_Url) Descriptor() ([]byte, []int) {
  return file_example_proto_rawDescGZIP(), []int{0, 0}
}

func (x *Http_Url) GetScheme() string {
  if x != nil {
    return x.Scheme
  }
  return ""
}

var File_example_proto protoreflect.FileDescriptor

var file_example_proto_rawDesc = []byte{
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}

var (
  file_example_proto_rawDescOnce sync.Once
  file_example_proto_rawDescData = file_example_proto_rawDesc
)

func file_example_proto_rawDescGZIP() []byte {
  file_example_proto_rawDescOnce.Do(func() {
    file_example_proto_rawDescData = protoimpl.X.CompressGZIP(file_example_proto_rawDescData)
  })
  return file_example_proto_rawDescData
}

var file_example_proto_msgTypes = make([]protoimpl.MessageInfo, 2)
var file_example_proto_goTypes = []interface{}{
  (*Http)(nil),     // 0: pb.Http
  (*Http_Url)(nil), // 1: pb.Http.Url
}
var file_example_proto_depIdxs = []int32{
  1, // 0: pb.Http.url:type_name -> pb.Http.Url
  1, // [1:1] is the sub-list for method output_type
  1, // [1:1] is the sub-list for method input_type
  1, // [1:1] is the sub-list for extension type_name
  1, // [1:1] is the sub-list for extension extendee
  0, // [0:1] is the sub-list for field type_name
}

func init() { file_example_proto_init() }
func file_example_proto_init() {
  if File_example_proto != nil {
    return
  }
  if !protoimpl.UnsafeEnabled {
    file_example_proto_msgTypes[0].Exporter = func(v interface{}, i int) interface{} {
      switch v := v.(*Http); i {
      case 0:
        return &v.state
      case 1:
        return &v.sizeCache
      case 2:
        return &v.unknownFields
      default:
        return nil
      }
    }
    file_example_proto_msgTypes[1].Exporter = func(v interface{}, i int) interface{} {
      switch v := v.(*Http_Url); i {
      case 0:
        return &v.state
      case 1:
        return &v.sizeCache
      case 2:
        return &v.unknownFields
      default:
        return nil
      }
    }
  }
  type x struct{}
  out := protoimpl.TypeBuilder{
    File: protoimpl.DescBuilder{
      GoPackagePath: reflect.TypeOf(x{}).PkgPath(),
      RawDescriptor: file_example_proto_rawDesc,
      NumEnums:      0,
      NumMessages:   2,
      NumExtensions: 0,
      NumServices:   0,
    },
    GoTypes:           file_example_proto_goTypes,
    DependencyIndexes: file_example_proto_depIdxs,
    MessageInfos:      file_example_proto_msgTypes,
  }.Build()
  File_example_proto = out.File
  file_example_proto_rawDesc = nil
  file_example_proto_goTypes = nil
  file_example_proto_depIdxs = nil
}

Download/Install

The easiest way to install is to run go get install github.com/searKing/golang/tools/protoc-gen-go-tag . You can also manually git clone the repository to $GOPATH/src/github.com/searKing/golang/tools/protoc-gen-go-tag .

protoc-gen-go-tag: program not found or is not executable

The protoc compiler expects to find plugins named proto-gen-xxx on the execution $PATH. So first:

export PATH=${PATH}:$(go env GOPATH)/bin

xxx.proto: Tried to write the same file twice.

• The protoc-gen-go-tag rewrites *.pb.go by proto-gen-go already. So use protoc-gen-go-tag instead of protoc-gen-go
• protoc-gen-go is installed by go get install google.golang.org/protobuf/cmd/protoc-gen-go
• Basically the magical incantation (apart from includes) is the --go-tag_out. That triggers the protoc-gen-go-tag plugin to generate *.pb.go. That's it :)

If you use protoc-gen-go installed by go get install github.com/golang/protobuf/protoc-gen-go

• github.com/golang/protobuf has been superseded by the google.golang.org/protobuf module
• install protoc-gen-go-tag by go get github.com/searKing/golang/tools/protoc-gen-go-tag@e27209892e58d3df53c587f1feefb6290af17d85
• protoc -I . --go_out=paths=source_relative:. --go-tag_out=paths=source_relative:. *.proto
• *.pb.go generated by protoc-gen-go will be rewritten by protoc-gen-go-tag

trick: embedded tag.proto into your proto directly, avoid include the tag.proto

• Step 1 replace import "github.com/searKing/golang/tools/protoc-gen-go-tag/tag/tag.proto"; with code in the tag.proto
• Step 2 replace google.protobuf.field_tag with field_tag

syntax = "proto3";

package pb;

// import "github.com/searKing/golang/tools/protoc-gen-go-tag/tag/tag.proto";
import "google/protobuf/descriptor.proto";
extend google.protobuf.FieldOptions {
  FieldTag field_tag = 65000;
}
message FieldTag {
  // struct tag.
  string struct_tag = 1;// custom struct tag
  UpdateStrategy update_strategy = 2;// update strategy

  enum UpdateStrategy {
    update = 0;// use custom struct tag to update struct tag generated by proto
    replace = 1;// use custom struct tag to replace struct tag generated by proto
  }
}

message Http{
  string protocol = 1;
  string version = 2[json_name = "Url", (field_tag) = {struct_tag: "validate:\"gte=0,lte=130\""}];;
  Url url = 3[json_name = "Url", (field_tag) = {struct_tag: "json:\"url_tag,omitempty\""}];
  message Url {
    string scheme = 1[json_name = "Scheme", (field_tag) = {struct_tag: "json:\"schema_tag,omitempty\""}];
    //  string scheme = 1[json_name = "Scheme"];
  }
}

Inspiring projects

• protobuf

Documentation

Overview

protoc-gen-go-tag is a plugin for the Google protocol buffer compiler to Generate Go code. Install it by building this program and making it accessible within your PATH with the name:

protoc-gen-go-tag

The 'go' suffix becomes part of the argument for the protocol compiler, such that it can be invoked as:

protoc --go-tag_out=paths=source_relative:. path/to/astFile.proto

This generates Go bindings for the protocol buffer defined by astFile.proto. With that input, the output will be written to:

path/to/astFile.pb.go

See the README and documentation for protocol buffers to learn more:

https://developers.google.com/protocol-buffers/