tarsgo为protoc-gen-go添加tarsrpc插件

tarsgo对Protobuf的支持是直接编写protoc-gen-go的插件，类似gRPC插件。
我们下面就利用tarsgo写的tarsrpc这个插件，一步步生成protoc-gen-go

首先我们引用《Go语言高级编程》中的介绍：
Protobuf的protoc编译器是通过插件机制实现对不同语言的支持。比如protoc命令出现--xxx_out格式的参数，那么protoc将首先查询是否有内置的xxx插件，如果没有内置的xxx插件那么将继续查询当前系统中是否存在protoc-gen-xxx命名的可执行程序，最终通过查询到的插件生成代码。对于Go语言的protoc-gen-go插件来说，里面又实现了一层静态插件系统。比如protoc-gen-go内置了一个gRPC插件，用户可以通过--go_out=plugins=grpc参数来生成gRPC相关代码，否则只会针对message生成相关代码。

参考gRPC插件的代码，可以发现generator.RegisterPlugin函数可以用来注册插件。插件是一个generator.Plugin接口：

// A Plugin provides functionality to add to the output during
// Go code generation, such as to produce RPC stubs.
type Plugin interface {
    // Name identifies the plugin.
    Name() string
    // Init is called once after data structures are built but before
    // code generation begins.
    Init(g *Generator)
    // Generate produces the code generated by the plugin for this file,
    // except for the imports, by calling the generator's methods P, In,
    // and Out.
    Generate(file *FileDescriptor)
    // GenerateImports produces the import declarations for this file.
    // It is called after Generate.
    GenerateImports(file *FileDescriptor)
}

第一步，我们创建一个叫protoc-gen-go的项目

第二步，goland打开，简单设置一下代理

第三步，初始化项目

go mod init protoc-gen-go

第四步，复制tarsrpc这个插件，地址如下：

https://github.com/TarsCloud/TarsGo/tree/master/tars/tools/pb2tarsgo/protoc-gen-go

将下面的tarsrpc文件夹复制到proto这个目录中,并添加main.go文件

第五步，安装https://github.com/golang/protobuf/ v1.3.5版本

go get github.com/golang/protobuf@v1.3.5

第六步，添加mian.go 引入tarsrpc

// Go support for Protocol Buffers - Google's data interchange format
//
// Copyright 2010 The Go Authors.  All rights reserved.
// https://github.com/golang/protobuf
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

// protoc-gen-go is a plugin for the Google protocol buffer compiler to generate
// Go code.  Run it by building this program and putting it in your path with
// the name
// 	protoc-gen-go
// That word 'go' at the end becomes part of the option string set for the
// protocol compiler, so once the protocol compiler (protoc) is installed
// you can run
// 	protoc --go_out=output_directory input_directory/file.proto
// to generate Go bindings for the protocol defined by file.proto.
// With that input, the output will be written to
// 	output_directory/file.pb.go
//
// The generated code is documented in the package comment for
// the library.
//
// See the README and documentation for protocol buffers to learn more:
// 	https://developers.google.com/protocol-buffers/
package main

import (
	"io/ioutil"
	"os"

	"github.com/golang/protobuf/proto"
	"github.com/golang/protobuf/protoc-gen-go/generator"
	_ "protoc-gen-go/tarsrpc"
)

func main() {
	// Begin by allocating a generator. The request and response structures are stored there
	// so we can do error handling easily - the response structure contains the field to
	// report failure.
	g := generator.New()

	data, err := ioutil.ReadAll(os.Stdin)
	if err != nil {
		g.Error(err, "reading input")
	}

	if err := proto.Unmarshal(data, g.Request); err != nil {
		g.Error(err, "parsing input proto")
	}

	if len(g.Request.FileToGenerate) == 0 {
		g.Fail("no files to generate")
	}

	g.CommandLineParameters(g.Request.GetParameter())

	// Create a wrapped version of the Descriptors and EnumDescriptors that
	// point to the file that defines them.
	g.WrapTypes()

	g.SetPackageNames()
	g.BuildTypeNameMap()

	g.GenerateAllFiles()

	// Send back the results.
	data, err = proto.Marshal(g.Response)
	if err != nil {
		g.Error(err, "failed to marshal output proto")
	}
	_, err = os.Stdout.Write(data)
	if err != nil {
		g.Error(err, "failed to write output proto")
	}
}

第七步，生成protoc-gen-go.exe

go build .

最后，我们得到了protoc-gen-go.exe，可以将这个程序放入$GOPATH/bin(go下面的bin目录)中使用。

参考资料:
《Go语言高级编程》
https://chai2010.cn/advanced-go-programming-book/ch4-rpc/ch4-02-pb-intro.html
《自定义 golang protobuf plugin》
https://blog.csdn.net/wanmei002/article/details/106097849/