任意の関数の情報を取得するための関数

func_info.go

import (
	"reflect"
	"regexp"
	"runtime"
	"strings"

	"github.com/pkg/errors"
)

/*
runtime.FuncForPC(...).Name() は下記のような文字列を返す
  fuga package にある fuga struct 経由で指定した場合
    github.com/app/repo/fuga.(fuga).Hello-fm
    # GetFuncInfo => {packageName: "fuga", parentName: "fuga", name: "Hello", isAnonymous: false}
    
  fuga package にある fuga struct のポインタ経由で指定した場合
    github.com/app/repo/fuga.(*fuga).Hello-fm
    # GetFuncInfo => {packageName: "fuga", parentName: "fuga", name: "Hello", isAnonymous: false}
    
  fuga package にある Fuga interface 経由で関数を指定した場合
    github.com/app/repo/fuga.(Fuga).Hello-fm
    # GetFuncInfo => {packageName: "fuga", parentName: "Fuga", name: "Hello", isAnonymous: false}
    
  fuga package のトップレベル関数
    github.com/app/repo/fuga.Hello
    # GetFuncInfo => {packageName: "fuga", parentName: "", name: "Hello", isAnonymous: false}
    
  fuga package のトップレベル関数内の無名関数
    github.com/app/repo/fuga.Hello.func1
    # GetFuncInfo => {packageName: "fuga", parentName: "", name: "Hello", isAnonymous: true}
    
  fuga package にある fuga struct のポインタ経由で Hello 関数内にある無名関数
    github.com/app/repo/fuga.(*fuga).Hello.func1
    # GetFuncInfo => {packageName: "fuga", parentName: "fuga", name: "Hello", isAnonymous: true}
    
  fuga package にある fuga struct のポインタ経由で Hello 関数内にある無名関数内の無名関数
    github.com/app/repo/fuga.(*fuga).Hello.func2.1
    # GetFuncInfo => {packageName: "fuga", parentName: "fuga", name: "Hello", isAnonymous: true}
    
*/

func IsFunc(v interface{}) bool {
	return reflect.TypeOf(v).Kind() == reflect.Func
}

/*
関数を受け取って、その関数が属するパッケージ名、struct/interface名、関数名、無名関数かどうか、を返す
*/
func GetFuncInfo(f interface{}) FuncInfo {
	if !IsFunc(f) {
		panic(errors.Errorf("argument f must be a function GetFuncInfo: %#v", f))
	}
	fv := reflect.ValueOf(f)
	fullName := runtime.FuncForPC(fv.Pointer()).Name()
	splits := strings.Split(fullName, "/")
	baseName := splits[len(splits)-1]
	normalizePattern := regexp.MustCompile(`[^a-zA-Z.-]`)
	plainName := normalizePattern.ReplaceAllString(baseName, "")
	isMethod := strings.Index(baseName, "(") >= 0
	names := strings.Split(plainName, ".")
	if len(names) <= 1 {
		panic(errors.Errorf("unexpected func name pattern GetFuncInfo: %+v", fullName))
	}
	packageName := names[0]
	parentName := ""
	name := ""
	isAnonymous := false
	if isMethod {
		parentName = names[1]
		name = removeHyphenSuffix(names[2])
		if len(names) >= 4 {
			isAnonymous = true
		}
	} else {
		name = removeHyphenSuffix(names[1])
		if len(names) >= 3 {
			isAnonymous = true
		}
	}
	return funcInfo{
		fullName:    fullName,
		packageName: packageName,
		parentName:  parentName,
		name:        name,
		isAnonymous: isAnonymous,
	}
}

func removeHyphenSuffix(funcName string) string {
	names := strings.Split(funcName, "-")
	return names[0]
}

type funcInfo struct {
	fullName    string
	packageName string
	parentName  string
	name        string
	isAnonymous bool
}

func (f funcInfo) PackageName() string {
	return f.packageName
}

func (f funcInfo) ParentName() string {
	return f.parentName
}

func (f funcInfo) Name() string {
	return f.name
}

func (f funcInfo) IsAnonymous() bool {
	return f.isAnonymous
}

type FuncInfo interface {
	PackageName() string
	ParentName() string
	Name() string
	IsAnonymous() bool
}