Parse go struct

parse_struct.go

package main

import (
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
	"strings"
)

const src = `package foo
import (
	"fmt"
	"time"
	"github.com/rs/xid"
)

// 用户档案
type UserProfile struct {
	xxx	int
	UserProfileID      xid.ID
	JmUserID           string
	NickName           *string
	NickNameInitial    string
	// 生日
	// 格式：yyyymmdd
	Birthday           time.Time
	Hand               int
	Gender             int
	Height             int
	Weight             int
	IsProfileCompleted bool
	CreatedAt          time.Time  // 创建时间
	UpdatedAt          time.Time  // 更新时间
	DeletedAt          *time.Time // 删除时间
}
`

func main() {
	fset := token.NewFileSet() // positions are relative to fset

	f, err := parser.ParseFile(fset, "", src, parser.ParseComments)
	if err != nil {
		fmt.Println(err)
		return
	}

	for _, d := range f.Decls {
		// is "type Xxxx struct" decleration
		if t, ok := d.(*ast.GenDecl); ok && t.Tok == token.TYPE {
			spec := t.Specs[0]

			if ts, ok := spec.(*ast.TypeSpec); ok {
				// DEBUG: print whole StructType
				// ast.Print(fset, ts)

				printStruct(ts)
			}
		}
	}
}

func printStruct(ts *ast.TypeSpec) {
	// is a struct
	st, ok := ts.Type.(*ast.StructType)
	if !ok {
		return
	}

	name := ts.Name

	if !name.IsExported() {
		// ignore not exported struct
		return
	}

	// print struct name
	fmt.Println("Struct:", name)

	// print fields
	for _, field := range st.Fields.List {
		printField(field)
	}
}

func printField(f *ast.Field) {
	n := f.Names[0] // name
	typ := fieldType(f.Type)
	var c string
	if f.Doc != nil { // 文档注释
		c = f.Doc.Text()
	} else if f.Comment != nil { // 行间注释
		c = f.Comment.Text()
	}
	c = strings.TrimSpace(c)

	// print exported field only; otherwise print nothing
	if n.IsExported() {
		// 注释
		if c != "" {
			fmt.Println(c)
		}
		// 定义
		fmt.Println(n.Name, typ)
	}
}

func fieldType(n ast.Node) string {
	typ := ""
	switch x := n.(type) {
	case *ast.Ident: // 标准类型
		typ = x.Name
	case *ast.SelectorExpr: // 包引用类型
		typ = fmt.Sprintf("%s.%s", x.X, x.Sel)
	case *ast.StarExpr: // 指针类型
		typ = "*" + fieldType(x.X)
	}

	return typ
}