go option 源码

  • 2022-07-15
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golang option 代码


// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// This file contains the code to handle template options.

package template

import "strings"

// missingKeyAction defines how to respond to indexing a map with a key that is not present.
type missingKeyAction int

const (
	mapInvalid   missingKeyAction = iota // Return an invalid reflect.Value.
	mapZeroValue                         // Return the zero value for the map element.
	mapError                             // Error out

type option struct {
	missingKey missingKeyAction

// Option sets options for the template. Options are described by
// strings, either a simple string or "key=value". There can be at
// most one equals sign in an option string. If the option string
// is unrecognized or otherwise invalid, Option panics.
// Known options:
// missingkey: Control the behavior during execution if a map is
// indexed with a key that is not present in the map.
//	"missingkey=default" or "missingkey=invalid"
//		The default behavior: Do nothing and continue execution.
//		If printed, the result of the index operation is the string
//		"<no value>".
//	"missingkey=zero"
//		The operation returns the zero value for the map type's element.
//	"missingkey=error"
//		Execution stops immediately with an error.
func (t *Template) Option(opt ...string) *Template {
	for _, s := range opt {
	return t

func (t *Template) setOption(opt string) {
	if opt == "" {
		panic("empty option string")
	// key=value
	if key, value, ok := strings.Cut(opt, "="); ok {
		switch key {
		case "missingkey":
			switch value {
			case "invalid", "default":
				t.option.missingKey = mapInvalid
			case "zero":
				t.option.missingKey = mapZeroValue
			case "error":
				t.option.missingKey = mapError
	panic("unrecognized option: " + opt)


go 源码目录


go doc 源码

go example_test 源码

go examplefiles_test 源码

go examplefunc_test 源码

go exec 源码

go exec_test 源码

go funcs 源码

go helper 源码

go link_test 源码

go multi_test 源码