Golang ast 的使用

  從文件中獲取註釋信息

package main

import (
	"go/ast"
	"go/parser"
	"go/token"
	"log"
	"path/filepath"
)

type Visitor struct {
	fset *token.FileSet
}

func (v *Visitor) Visit(node ast.Node) ast.Visitor {
	switch node.(type) {
	//判斷ast分類
	case *ast.FuncDecl:
		demo := node.(*ast.FuncDecl)

		// 打印具體的註釋
		println(demo.Doc.List[0].Text)

		// 可以打印出ast結構
		ast.Print(v.fset, node)
	}

	return v
}

func main() {
	fset := token.NewFileSet()

	path, _ := filepath.Abs("./demo.go")
	f, err := parser.ParseFile(fset, path, nil, parser.ParseComments)
	if err != nil {
		log.Println(err)
		return
	}

	ast.Walk(&Visitor{
		fset: fset,
	}, f)

}

demo.go 被分析文件

// file commment
package main

type Article struct{}

// @GET("/get")
func (a Article) Get() {

}

// @POST("/save")
func (a Article) Save() {

}

　輸出：

// @GET("/get")
// @POST("/save")

  向文件中添加變量

package main

import (
	"bytes"
	"fmt"
	"go/ast"
	"go/format"
	"go/parser"
	"go/token"
	"log"
	"os"
	"path/filepath"
)

type Visitor struct {
	fset *token.FileSet
}

func (v *Visitor) Visit(node ast.Node) ast.Visitor {
	switch node.(type) {
	//判斷ast分類
	case *ast.FuncDecl:
		demo := node.(*ast.FuncDecl)
		if demo.Name.Name == "GetModels" {

			returnStm, ok := demo.Body.List[0].(*ast.ReturnStmt)
			if !ok {
				return v
			}

			comp, ok := returnStm.Results[0].(*ast.CompositeLit)
			if !ok {
				return v
			}

			comp.Elts = append(comp.Elts, &ast.UnaryExpr{
				Op: token.AND,
				X: &ast.CompositeLit{
					Type: &ast.Ident{
						Name: "Test",
					},
				},
			})

		}

	}

	return v
}

func main() {
	fset := token.NewFileSet()

	path, _ := filepath.Abs("./models/demo.go")
	f, err := parser.ParseFile(fset, path, nil, parser.ParseComments)
	if err != nil {
		log.Println(err)
		return
	}

	ast.Walk(&Visitor{
		fset: fset,
	}, f)

	// ast.Print(fset, f)
	var output []byte
	buffer := bytes.NewBuffer(output)
	err = format.Node(buffer, fset, f)
	if err != nil {
		log.Fatal(err)
	}
	// 輸出Go代碼
	file, err := os.OpenFile(path, os.O_RDWR, 0766)
	if err != nil {
		log.Fatalf("open err %s", err.Error())
	}
	n, err := file.Write(buffer.Bytes())
	if err != nil {
		log.Fatalf("write err %s", err.Error())
	}
	fmt.Println(n)
	fmt.Println(buffer.String())

}

demo.go

/*
 * @Description:
 * @Author: gphper
 * @Date: 2021-07-08 20:12:04
 */
package models

import (
	"context"

	"github.com/gphper/ginadmin/configs"
	"github.com/gphper/ginadmin/pkg/loggers"
	"gorm.io/driver/mysql"

	"gorm.io/gorm"
	"gorm.io/gorm/logger"
	"gorm.io/gorm/schema"
)

var mapDB map[string]*gorm.DB

type GaTabler interface {
	schema.Tabler
	FillData(*gorm.DB)
	GetConnName() string
}

type BaseModle struct {
	ConnName string `gorm:"-" json:"-"`
}

func (b *BaseModle) TableName() string {
	return ""
}

func (b *BaseModle) FillData(db *gorm.DB) {}

func (b *BaseModle) GetConnName() string {
	return b.ConnName
}

// 獲取鏈接
func GetDB(model GaTabler) *gorm.DB {

	db, ok := mapDB[model.GetConnName()]
	if !ok {
		errMsg := fmt.Sprintf("connection name%s no exists", model.GetConnName())
		loggers.LogError(context.Background(), "get_db_error", "GetDB", map[string]string{
			"msg": errMsg,
		})
	}
	return db
}


func GetModels() []interface{} {
	return []interface{}{
		&AdminUsers{}, &Article{}, &UploadType{}, &User{}
	}
}　

最終結果向 GetModels 中添加 &Test{}