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Run Format

Source file src/text/template/exec_test.go

  // Copyright 2011 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.
  
  package template
  
  import (
  	"bytes"
  	"errors"
  	"flag"
  	"fmt"
  	"io/ioutil"
  	"reflect"
  	"strings"
  	"testing"
  )
  
  var debug = flag.Bool("debug", false, "show the errors produced by the tests")
  
  // T has lots of interesting pieces to use to test execution.
  type T struct {
  	// Basics
  	True        bool
  	I           int
  	U16         uint16
  	X           string
  	FloatZero   float64
  	ComplexZero complex128
  	// Nested structs.
  	U *U
  	// Struct with String method.
  	V0     V
  	V1, V2 *V
  	// Struct with Error method.
  	W0     W
  	W1, W2 *W
  	// Slices
  	SI      []int
  	SIEmpty []int
  	SB      []bool
  	// Maps
  	MSI      map[string]int
  	MSIone   map[string]int // one element, for deterministic output
  	MSIEmpty map[string]int
  	MXI      map[interface{}]int
  	MII      map[int]int
  	SMSI     []map[string]int
  	// Empty interfaces; used to see if we can dig inside one.
  	Empty0 interface{} // nil
  	Empty1 interface{}
  	Empty2 interface{}
  	Empty3 interface{}
  	Empty4 interface{}
  	// Non-empty interfaces.
  	NonEmptyInterface    I
  	NonEmptyInterfacePtS *I
  	// Stringer.
  	Str fmt.Stringer
  	Err error
  	// Pointers
  	PI  *int
  	PS  *string
  	PSI *[]int
  	NIL *int
  	// Function (not method)
  	BinaryFunc      func(string, string) string
  	VariadicFunc    func(...string) string
  	VariadicFuncInt func(int, ...string) string
  	NilOKFunc       func(*int) bool
  	ErrFunc         func() (string, error)
  	// Template to test evaluation of templates.
  	Tmpl *Template
  	// Unexported field; cannot be accessed by template.
  	unexported int
  }
  
  type S []string
  
  func (S) Method0() string {
  	return "M0"
  }
  
  type U struct {
  	V string
  }
  
  type V struct {
  	j int
  }
  
  func (v *V) String() string {
  	if v == nil {
  		return "nilV"
  	}
  	return fmt.Sprintf("<%d>", v.j)
  }
  
  type W struct {
  	k int
  }
  
  func (w *W) Error() string {
  	if w == nil {
  		return "nilW"
  	}
  	return fmt.Sprintf("[%d]", w.k)
  }
  
  var siVal = I(S{"a", "b"})
  
  var tVal = &T{
  	True:   true,
  	I:      17,
  	U16:    16,
  	X:      "x",
  	U:      &U{"v"},
  	V0:     V{6666},
  	V1:     &V{7777}, // leave V2 as nil
  	W0:     W{888},
  	W1:     &W{999}, // leave W2 as nil
  	SI:     []int{3, 4, 5},
  	SB:     []bool{true, false},
  	MSI:    map[string]int{"one": 1, "two": 2, "three": 3},
  	MSIone: map[string]int{"one": 1},
  	MXI:    map[interface{}]int{"one": 1},
  	MII:    map[int]int{1: 1},
  	SMSI: []map[string]int{
  		{"one": 1, "two": 2},
  		{"eleven": 11, "twelve": 12},
  	},
  	Empty1:               3,
  	Empty2:               "empty2",
  	Empty3:               []int{7, 8},
  	Empty4:               &U{"UinEmpty"},
  	NonEmptyInterface:    &T{X: "x"},
  	NonEmptyInterfacePtS: &siVal,
  	Str:                  bytes.NewBuffer([]byte("foozle")),
  	Err:                  errors.New("erroozle"),
  	PI:                   newInt(23),
  	PS:                   newString("a string"),
  	PSI:                  newIntSlice(21, 22, 23),
  	BinaryFunc:           func(a, b string) string { return fmt.Sprintf("[%s=%s]", a, b) },
  	VariadicFunc:         func(s ...string) string { return fmt.Sprint("<", strings.Join(s, "+"), ">") },
  	VariadicFuncInt:      func(a int, s ...string) string { return fmt.Sprint(a, "=<", strings.Join(s, "+"), ">") },
  	NilOKFunc:            func(s *int) bool { return s == nil },
  	ErrFunc:              func() (string, error) { return "bla", nil },
  	Tmpl:                 Must(New("x").Parse("test template")), // "x" is the value of .X
  }
  
  // A non-empty interface.
  type I interface {
  	Method0() string
  }
  
  var iVal I = tVal
  
  // Helpers for creation.
  func newInt(n int) *int {
  	return &n
  }
  
  func newString(s string) *string {
  	return &s
  }
  
  func newIntSlice(n ...int) *[]int {
  	p := new([]int)
  	*p = make([]int, len(n))
  	copy(*p, n)
  	return p
  }
  
  // Simple methods with and without arguments.
  func (t *T) Method0() string {
  	return "M0"
  }
  
  func (t *T) Method1(a int) int {
  	return a
  }
  
  func (t *T) Method2(a uint16, b string) string {
  	return fmt.Sprintf("Method2: %d %s", a, b)
  }
  
  func (t *T) Method3(v interface{}) string {
  	return fmt.Sprintf("Method3: %v", v)
  }
  
  func (t *T) Copy() *T {
  	n := new(T)
  	*n = *t
  	return n
  }
  
  func (t *T) MAdd(a int, b []int) []int {
  	v := make([]int, len(b))
  	for i, x := range b {
  		v[i] = x + a
  	}
  	return v
  }
  
  var myError = errors.New("my error")
  
  // MyError returns a value and an error according to its argument.
  func (t *T) MyError(error bool) (bool, error) {
  	if error {
  		return true, myError
  	}
  	return false, nil
  }
  
  // A few methods to test chaining.
  func (t *T) GetU() *U {
  	return t.U
  }
  
  func (u *U) TrueFalse(b bool) string {
  	if b {
  		return "true"
  	}
  	return ""
  }
  
  func typeOf(arg interface{}) string {
  	return fmt.Sprintf("%T", arg)
  }
  
  type execTest struct {
  	name   string
  	input  string
  	output string
  	data   interface{}
  	ok     bool
  }
  
  // bigInt and bigUint are hex string representing numbers either side
  // of the max int boundary.
  // We do it this way so the test doesn't depend on ints being 32 bits.
  var (
  	bigInt  = fmt.Sprintf("0x%x", int(1<<uint(reflect.TypeOf(0).Bits()-1)-1))
  	bigUint = fmt.Sprintf("0x%x", uint(1<<uint(reflect.TypeOf(0).Bits()-1)))
  )
  
  var execTests = []execTest{
  	// Trivial cases.
  	{"empty", "", "", nil, true},
  	{"text", "some text", "some text", nil, true},
  	{"nil action", "{{nil}}", "", nil, false},
  
  	// Ideal constants.
  	{"ideal int", "{{typeOf 3}}", "int", 0, true},
  	{"ideal float", "{{typeOf 1.0}}", "float64", 0, true},
  	{"ideal exp float", "{{typeOf 1e1}}", "float64", 0, true},
  	{"ideal complex", "{{typeOf 1i}}", "complex128", 0, true},
  	{"ideal int", "{{typeOf " + bigInt + "}}", "int", 0, true},
  	{"ideal too big", "{{typeOf " + bigUint + "}}", "", 0, false},
  	{"ideal nil without type", "{{nil}}", "", 0, false},
  
  	// Fields of structs.
  	{".X", "-{{.X}}-", "-x-", tVal, true},
  	{".U.V", "-{{.U.V}}-", "-v-", tVal, true},
  	{".unexported", "{{.unexported}}", "", tVal, false},
  
  	// Fields on maps.
  	{"map .one", "{{.MSI.one}}", "1", tVal, true},
  	{"map .two", "{{.MSI.two}}", "2", tVal, true},
  	{"map .NO", "{{.MSI.NO}}", "<no value>", tVal, true},
  	{"map .one interface", "{{.MXI.one}}", "1", tVal, true},
  	{"map .WRONG args", "{{.MSI.one 1}}", "", tVal, false},
  	{"map .WRONG type", "{{.MII.one}}", "", tVal, false},
  
  	// Dots of all kinds to test basic evaluation.
  	{"dot int", "<{{.}}>", "<13>", 13, true},
  	{"dot uint", "<{{.}}>", "<14>", uint(14), true},
  	{"dot float", "<{{.}}>", "<15.1>", 15.1, true},
  	{"dot bool", "<{{.}}>", "<true>", true, true},
  	{"dot complex", "<{{.}}>", "<(16.2-17i)>", 16.2 - 17i, true},
  	{"dot string", "<{{.}}>", "<hello>", "hello", true},
  	{"dot slice", "<{{.}}>", "<[-1 -2 -3]>", []int{-1, -2, -3}, true},
  	{"dot map", "<{{.}}>", "<map[two:22]>", map[string]int{"two": 22}, true},
  	{"dot struct", "<{{.}}>", "<{7 seven}>", struct {
  		a int
  		b string
  	}{7, "seven"}, true},
  
  	// Variables.
  	{"$ int", "{{$}}", "123", 123, true},
  	{"$.I", "{{$.I}}", "17", tVal, true},
  	{"$.U.V", "{{$.U.V}}", "v", tVal, true},
  	{"declare in action", "{{$x := $.U.V}}{{$x}}", "v", tVal, true},
  
  	// Type with String method.
  	{"V{6666}.String()", "-{{.V0}}-", "-<6666>-", tVal, true},
  	{"&V{7777}.String()", "-{{.V1}}-", "-<7777>-", tVal, true},
  	{"(*V)(nil).String()", "-{{.V2}}-", "-nilV-", tVal, true},
  
  	// Type with Error method.
  	{"W{888}.Error()", "-{{.W0}}-", "-[888]-", tVal, true},
  	{"&W{999}.Error()", "-{{.W1}}-", "-[999]-", tVal, true},
  	{"(*W)(nil).Error()", "-{{.W2}}-", "-nilW-", tVal, true},
  
  	// Pointers.
  	{"*int", "{{.PI}}", "23", tVal, true},
  	{"*string", "{{.PS}}", "a string", tVal, true},
  	{"*[]int", "{{.PSI}}", "[21 22 23]", tVal, true},
  	{"*[]int[1]", "{{index .PSI 1}}", "22", tVal, true},
  	{"NIL", "{{.NIL}}", "<nil>", tVal, true},
  
  	// Empty interfaces holding values.
  	{"empty nil", "{{.Empty0}}", "<no value>", tVal, true},
  	{"empty with int", "{{.Empty1}}", "3", tVal, true},
  	{"empty with string", "{{.Empty2}}", "empty2", tVal, true},
  	{"empty with slice", "{{.Empty3}}", "[7 8]", tVal, true},
  	{"empty with struct", "{{.Empty4}}", "{UinEmpty}", tVal, true},
  	{"empty with struct, field", "{{.Empty4.V}}", "UinEmpty", tVal, true},
  
  	// Method calls.
  	{".Method0", "-{{.Method0}}-", "-M0-", tVal, true},
  	{".Method1(1234)", "-{{.Method1 1234}}-", "-1234-", tVal, true},
  	{".Method1(.I)", "-{{.Method1 .I}}-", "-17-", tVal, true},
  	{".Method2(3, .X)", "-{{.Method2 3 .X}}-", "-Method2: 3 x-", tVal, true},
  	{".Method2(.U16, `str`)", "-{{.Method2 .U16 `str`}}-", "-Method2: 16 str-", tVal, true},
  	{".Method2(.U16, $x)", "{{if $x := .X}}-{{.Method2 .U16 $x}}{{end}}-", "-Method2: 16 x-", tVal, true},
  	{".Method3(nil constant)", "-{{.Method3 nil}}-", "-Method3: <nil>-", tVal, true},
  	{".Method3(nil value)", "-{{.Method3 .MXI.unset}}-", "-Method3: <nil>-", tVal, true},
  	{"method on var", "{{if $x := .}}-{{$x.Method2 .U16 $x.X}}{{end}}-", "-Method2: 16 x-", tVal, true},
  	{"method on chained var",
  		"{{range .MSIone}}{{if $.U.TrueFalse $.True}}{{$.U.TrueFalse $.True}}{{else}}WRONG{{end}}{{end}}",
  		"true", tVal, true},
  	{"chained method",
  		"{{range .MSIone}}{{if $.GetU.TrueFalse $.True}}{{$.U.TrueFalse $.True}}{{else}}WRONG{{end}}{{end}}",
  		"true", tVal, true},
  	{"chained method on variable",
  		"{{with $x := .}}{{with .SI}}{{$.GetU.TrueFalse $.True}}{{end}}{{end}}",
  		"true", tVal, true},
  	{".NilOKFunc not nil", "{{call .NilOKFunc .PI}}", "false", tVal, true},
  	{".NilOKFunc nil", "{{call .NilOKFunc nil}}", "true", tVal, true},
  
  	// Function call builtin.
  	{".BinaryFunc", "{{call .BinaryFunc `1` `2`}}", "[1=2]", tVal, true},
  	{".VariadicFunc0", "{{call .VariadicFunc}}", "<>", tVal, true},
  	{".VariadicFunc2", "{{call .VariadicFunc `he` `llo`}}", "<he+llo>", tVal, true},
  	{".VariadicFuncInt", "{{call .VariadicFuncInt 33 `he` `llo`}}", "33=<he+llo>", tVal, true},
  	{"if .BinaryFunc call", "{{ if .BinaryFunc}}{{call .BinaryFunc `1` `2`}}{{end}}", "[1=2]", tVal, true},
  	{"if not .BinaryFunc call", "{{ if not .BinaryFunc}}{{call .BinaryFunc `1` `2`}}{{else}}No{{end}}", "No", tVal, true},
  	{"Interface Call", `{{stringer .S}}`, "foozle", map[string]interface{}{"S": bytes.NewBufferString("foozle")}, true},
  	{".ErrFunc", "{{call .ErrFunc}}", "bla", tVal, true},
  	{"call nil", "{{call nil}}", "", tVal, false},
  
  	// Erroneous function calls (check args).
  	{".BinaryFuncTooFew", "{{call .BinaryFunc `1`}}", "", tVal, false},
  	{".BinaryFuncTooMany", "{{call .BinaryFunc `1` `2` `3`}}", "", tVal, false},
  	{".BinaryFuncBad0", "{{call .BinaryFunc 1 3}}", "", tVal, false},
  	{".BinaryFuncBad1", "{{call .BinaryFunc `1` 3}}", "", tVal, false},
  	{".VariadicFuncBad0", "{{call .VariadicFunc 3}}", "", tVal, false},
  	{".VariadicFuncIntBad0", "{{call .VariadicFuncInt}}", "", tVal, false},
  	{".VariadicFuncIntBad`", "{{call .VariadicFuncInt `x`}}", "", tVal, false},
  	{".VariadicFuncNilBad", "{{call .VariadicFunc nil}}", "", tVal, false},
  
  	// Pipelines.
  	{"pipeline", "-{{.Method0 | .Method2 .U16}}-", "-Method2: 16 M0-", tVal, true},
  	{"pipeline func", "-{{call .VariadicFunc `llo` | call .VariadicFunc `he` }}-", "-<he+<llo>>-", tVal, true},
  
  	// Parenthesized expressions
  	{"parens in pipeline", "{{printf `%d %d %d` (1) (2 | add 3) (add 4 (add 5 6))}}", "1 5 15", tVal, true},
  
  	// Parenthesized expressions with field accesses
  	{"parens: $ in paren", "{{($).X}}", "x", tVal, true},
  	{"parens: $.GetU in paren", "{{($.GetU).V}}", "v", tVal, true},
  	{"parens: $ in paren in pipe", "{{($ | echo).X}}", "x", tVal, true},
  	{"parens: spaces and args", `{{(makemap "up" "down" "left" "right").left}}`, "right", tVal, true},
  
  	// If.
  	{"if true", "{{if true}}TRUE{{end}}", "TRUE", tVal, true},
  	{"if false", "{{if false}}TRUE{{else}}FALSE{{end}}", "FALSE", tVal, true},
  	{"if nil", "{{if nil}}TRUE{{end}}", "", tVal, false},
  	{"if 1", "{{if 1}}NON-ZERO{{else}}ZERO{{end}}", "NON-ZERO", tVal, true},
  	{"if 0", "{{if 0}}NON-ZERO{{else}}ZERO{{end}}", "ZERO", tVal, true},
  	{"if 1.5", "{{if 1.5}}NON-ZERO{{else}}ZERO{{end}}", "NON-ZERO", tVal, true},
  	{"if 0.0", "{{if .FloatZero}}NON-ZERO{{else}}ZERO{{end}}", "ZERO", tVal, true},
  	{"if 1.5i", "{{if 1.5i}}NON-ZERO{{else}}ZERO{{end}}", "NON-ZERO", tVal, true},
  	{"if 0.0i", "{{if .ComplexZero}}NON-ZERO{{else}}ZERO{{end}}", "ZERO", tVal, true},
  	{"if emptystring", "{{if ``}}NON-EMPTY{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
  	{"if string", "{{if `notempty`}}NON-EMPTY{{else}}EMPTY{{end}}", "NON-EMPTY", tVal, true},
  	{"if emptyslice", "{{if .SIEmpty}}NON-EMPTY{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
  	{"if slice", "{{if .SI}}NON-EMPTY{{else}}EMPTY{{end}}", "NON-EMPTY", tVal, true},
  	{"if emptymap", "{{if .MSIEmpty}}NON-EMPTY{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
  	{"if map", "{{if .MSI}}NON-EMPTY{{else}}EMPTY{{end}}", "NON-EMPTY", tVal, true},
  	{"if map unset", "{{if .MXI.none}}NON-ZERO{{else}}ZERO{{end}}", "ZERO", tVal, true},
  	{"if map not unset", "{{if not .MXI.none}}ZERO{{else}}NON-ZERO{{end}}", "ZERO", tVal, true},
  	{"if $x with $y int", "{{if $x := true}}{{with $y := .I}}{{$x}},{{$y}}{{end}}{{end}}", "true,17", tVal, true},
  	{"if $x with $x int", "{{if $x := true}}{{with $x := .I}}{{$x}},{{end}}{{$x}}{{end}}", "17,true", tVal, true},
  	{"if else if", "{{if false}}FALSE{{else if true}}TRUE{{end}}", "TRUE", tVal, true},
  	{"if else chain", "{{if eq 1 3}}1{{else if eq 2 3}}2{{else if eq 3 3}}3{{end}}", "3", tVal, true},
  
  	// Print etc.
  	{"print", `{{print "hello, print"}}`, "hello, print", tVal, true},
  	{"print 123", `{{print 1 2 3}}`, "1 2 3", tVal, true},
  	{"print nil", `{{print nil}}`, "<nil>", tVal, true},
  	{"println", `{{println 1 2 3}}`, "1 2 3\n", tVal, true},
  	{"printf int", `{{printf "%04x" 127}}`, "007f", tVal, true},
  	{"printf float", `{{printf "%g" 3.5}}`, "3.5", tVal, true},
  	{"printf complex", `{{printf "%g" 1+7i}}`, "(1+7i)", tVal, true},
  	{"printf string", `{{printf "%s" "hello"}}`, "hello", tVal, true},
  	{"printf function", `{{printf "%#q" zeroArgs}}`, "`zeroArgs`", tVal, true},
  	{"printf field", `{{printf "%s" .U.V}}`, "v", tVal, true},
  	{"printf method", `{{printf "%s" .Method0}}`, "M0", tVal, true},
  	{"printf dot", `{{with .I}}{{printf "%d" .}}{{end}}`, "17", tVal, true},
  	{"printf var", `{{with $x := .I}}{{printf "%d" $x}}{{end}}`, "17", tVal, true},
  	{"printf lots", `{{printf "%d %s %g %s" 127 "hello" 7-3i .Method0}}`, "127 hello (7-3i) M0", tVal, true},
  
  	// HTML.
  	{"html", `{{html "<script>alert(\"XSS\");</script>"}}`,
  		"&lt;script&gt;alert(&#34;XSS&#34;);&lt;/script&gt;", nil, true},
  	{"html pipeline", `{{printf "<script>alert(\"XSS\");</script>" | html}}`,
  		"&lt;script&gt;alert(&#34;XSS&#34;);&lt;/script&gt;", nil, true},
  	{"html", `{{html .PS}}`, "a string", tVal, true},
  
  	// JavaScript.
  	{"js", `{{js .}}`, `It\'d be nice.`, `It'd be nice.`, true},
  
  	// URL query.
  	{"urlquery", `{{"http://www.example.org/"|urlquery}}`, "http%3A%2F%2Fwww.example.org%2F", nil, true},
  
  	// Booleans
  	{"not", "{{not true}} {{not false}}", "false true", nil, true},
  	{"and", "{{and false 0}} {{and 1 0}} {{and 0 true}} {{and 1 1}}", "false 0 0 1", nil, true},
  	{"or", "{{or 0 0}} {{or 1 0}} {{or 0 true}} {{or 1 1}}", "0 1 true 1", nil, true},
  	{"boolean if", "{{if and true 1 `hi`}}TRUE{{else}}FALSE{{end}}", "TRUE", tVal, true},
  	{"boolean if not", "{{if and true 1 `hi` | not}}TRUE{{else}}FALSE{{end}}", "FALSE", nil, true},
  
  	// Indexing.
  	{"slice[0]", "{{index .SI 0}}", "3", tVal, true},
  	{"slice[1]", "{{index .SI 1}}", "4", tVal, true},
  	{"slice[HUGE]", "{{index .SI 10}}", "", tVal, false},
  	{"slice[WRONG]", "{{index .SI `hello`}}", "", tVal, false},
  	{"slice[nil]", "{{index .SI nil}}", "", tVal, false},
  	{"map[one]", "{{index .MSI `one`}}", "1", tVal, true},
  	{"map[two]", "{{index .MSI `two`}}", "2", tVal, true},
  	{"map[NO]", "{{index .MSI `XXX`}}", "0", tVal, true},
  	{"map[nil]", "{{index .MSI nil}}", "", tVal, false},
  	{"map[``]", "{{index .MSI ``}}", "0", tVal, true},
  	{"map[WRONG]", "{{index .MSI 10}}", "", tVal, false},
  	{"double index", "{{index .SMSI 1 `eleven`}}", "11", tVal, true},
  	{"nil[1]", "{{index nil 1}}", "", tVal, false},
  
  	// Len.
  	{"slice", "{{len .SI}}", "3", tVal, true},
  	{"map", "{{len .MSI }}", "3", tVal, true},
  	{"len of int", "{{len 3}}", "", tVal, false},
  	{"len of nothing", "{{len .Empty0}}", "", tVal, false},
  
  	// With.
  	{"with true", "{{with true}}{{.}}{{end}}", "true", tVal, true},
  	{"with false", "{{with false}}{{.}}{{else}}FALSE{{end}}", "FALSE", tVal, true},
  	{"with 1", "{{with 1}}{{.}}{{else}}ZERO{{end}}", "1", tVal, true},
  	{"with 0", "{{with 0}}{{.}}{{else}}ZERO{{end}}", "ZERO", tVal, true},
  	{"with 1.5", "{{with 1.5}}{{.}}{{else}}ZERO{{end}}", "1.5", tVal, true},
  	{"with 0.0", "{{with .FloatZero}}{{.}}{{else}}ZERO{{end}}", "ZERO", tVal, true},
  	{"with 1.5i", "{{with 1.5i}}{{.}}{{else}}ZERO{{end}}", "(0+1.5i)", tVal, true},
  	{"with 0.0i", "{{with .ComplexZero}}{{.}}{{else}}ZERO{{end}}", "ZERO", tVal, true},
  	{"with emptystring", "{{with ``}}{{.}}{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
  	{"with string", "{{with `notempty`}}{{.}}{{else}}EMPTY{{end}}", "notempty", tVal, true},
  	{"with emptyslice", "{{with .SIEmpty}}{{.}}{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
  	{"with slice", "{{with .SI}}{{.}}{{else}}EMPTY{{end}}", "[3 4 5]", tVal, true},
  	{"with emptymap", "{{with .MSIEmpty}}{{.}}{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
  	{"with map", "{{with .MSIone}}{{.}}{{else}}EMPTY{{end}}", "map[one:1]", tVal, true},
  	{"with empty interface, struct field", "{{with .Empty4}}{{.V}}{{end}}", "UinEmpty", tVal, true},
  	{"with $x int", "{{with $x := .I}}{{$x}}{{end}}", "17", tVal, true},
  	{"with $x struct.U.V", "{{with $x := $}}{{$x.U.V}}{{end}}", "v", tVal, true},
  	{"with variable and action", "{{with $x := $}}{{$y := $.U.V}}{{$y}}{{end}}", "v", tVal, true},
  
  	// Range.
  	{"range []int", "{{range .SI}}-{{.}}-{{end}}", "-3--4--5-", tVal, true},
  	{"range empty no else", "{{range .SIEmpty}}-{{.}}-{{end}}", "", tVal, true},
  	{"range []int else", "{{range .SI}}-{{.}}-{{else}}EMPTY{{end}}", "-3--4--5-", tVal, true},
  	{"range empty else", "{{range .SIEmpty}}-{{.}}-{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
  	{"range []bool", "{{range .SB}}-{{.}}-{{end}}", "-true--false-", tVal, true},
  	{"range []int method", "{{range .SI | .MAdd .I}}-{{.}}-{{end}}", "-20--21--22-", tVal, true},
  	{"range map", "{{range .MSI}}-{{.}}-{{end}}", "-1--3--2-", tVal, true},
  	{"range empty map no else", "{{range .MSIEmpty}}-{{.}}-{{end}}", "", tVal, true},
  	{"range map else", "{{range .MSI}}-{{.}}-{{else}}EMPTY{{end}}", "-1--3--2-", tVal, true},
  	{"range empty map else", "{{range .MSIEmpty}}-{{.}}-{{else}}EMPTY{{end}}", "EMPTY", tVal, true},
  	{"range empty interface", "{{range .Empty3}}-{{.}}-{{else}}EMPTY{{end}}", "-7--8-", tVal, true},
  	{"range empty nil", "{{range .Empty0}}-{{.}}-{{end}}", "", tVal, true},
  	{"range $x SI", "{{range $x := .SI}}<{{$x}}>{{end}}", "<3><4><5>", tVal, true},
  	{"range $x $y SI", "{{range $x, $y := .SI}}<{{$x}}={{$y}}>{{end}}", "<0=3><1=4><2=5>", tVal, true},
  	{"range $x MSIone", "{{range $x := .MSIone}}<{{$x}}>{{end}}", "<1>", tVal, true},
  	{"range $x $y MSIone", "{{range $x, $y := .MSIone}}<{{$x}}={{$y}}>{{end}}", "<one=1>", tVal, true},
  	{"range $x PSI", "{{range $x := .PSI}}<{{$x}}>{{end}}", "<21><22><23>", tVal, true},
  	{"declare in range", "{{range $x := .PSI}}<{{$foo:=$x}}{{$x}}>{{end}}", "<21><22><23>", tVal, true},
  	{"range count", `{{range $i, $x := count 5}}[{{$i}}]{{$x}}{{end}}`, "[0]a[1]b[2]c[3]d[4]e", tVal, true},
  	{"range nil count", `{{range $i, $x := count 0}}{{else}}empty{{end}}`, "empty", tVal, true},
  
  	// Cute examples.
  	{"or as if true", `{{or .SI "slice is empty"}}`, "[3 4 5]", tVal, true},
  	{"or as if false", `{{or .SIEmpty "slice is empty"}}`, "slice is empty", tVal, true},
  
  	// Error handling.
  	{"error method, error", "{{.MyError true}}", "", tVal, false},
  	{"error method, no error", "{{.MyError false}}", "false", tVal, true},
  
  	// Fixed bugs.
  	// Must separate dot and receiver; otherwise args are evaluated with dot set to variable.
  	{"bug0", "{{range .MSIone}}{{if $.Method1 .}}X{{end}}{{end}}", "X", tVal, true},
  	// Do not loop endlessly in indirect for non-empty interfaces.
  	// The bug appears with *interface only; looped forever.
  	{"bug1", "{{.Method0}}", "M0", &iVal, true},
  	// Was taking address of interface field, so method set was empty.
  	{"bug2", "{{$.NonEmptyInterface.Method0}}", "M0", tVal, true},
  	// Struct values were not legal in with - mere oversight.
  	{"bug3", "{{with $}}{{.Method0}}{{end}}", "M0", tVal, true},
  	// Nil interface values in if.
  	{"bug4", "{{if .Empty0}}non-nil{{else}}nil{{end}}", "nil", tVal, true},
  	// Stringer.
  	{"bug5", "{{.Str}}", "foozle", tVal, true},
  	{"bug5a", "{{.Err}}", "erroozle", tVal, true},
  	// Args need to be indirected and dereferenced sometimes.
  	{"bug6a", "{{vfunc .V0 .V1}}", "vfunc", tVal, true},
  	{"bug6b", "{{vfunc .V0 .V0}}", "vfunc", tVal, true},
  	{"bug6c", "{{vfunc .V1 .V0}}", "vfunc", tVal, true},
  	{"bug6d", "{{vfunc .V1 .V1}}", "vfunc", tVal, true},
  	// Legal parse but illegal execution: non-function should have no arguments.
  	{"bug7a", "{{3 2}}", "", tVal, false},
  	{"bug7b", "{{$x := 1}}{{$x 2}}", "", tVal, false},
  	{"bug7c", "{{$x := 1}}{{3 | $x}}", "", tVal, false},
  	// Pipelined arg was not being type-checked.
  	{"bug8a", "{{3|oneArg}}", "", tVal, false},
  	{"bug8b", "{{4|dddArg 3}}", "", tVal, false},
  	// A bug was introduced that broke map lookups for lower-case names.
  	{"bug9", "{{.cause}}", "neglect", map[string]string{"cause": "neglect"}, true},
  	// Field chain starting with function did not work.
  	{"bug10", "{{mapOfThree.three}}-{{(mapOfThree).three}}", "3-3", 0, true},
  	// Dereferencing nil pointer while evaluating function arguments should not panic. Issue 7333.
  	{"bug11", "{{valueString .PS}}", "", T{}, false},
  	// 0xef gave constant type float64. Issue 8622.
  	{"bug12xe", "{{printf `%T` 0xef}}", "int", T{}, true},
  	{"bug12xE", "{{printf `%T` 0xEE}}", "int", T{}, true},
  	{"bug12Xe", "{{printf `%T` 0Xef}}", "int", T{}, true},
  	{"bug12XE", "{{printf `%T` 0XEE}}", "int", T{}, true},
  	// Chained nodes did not work as arguments. Issue 8473.
  	{"bug13", "{{print (.Copy).I}}", "17", tVal, true},
  	// Didn't protect against nil or literal values in field chains.
  	{"bug14a", "{{(nil).True}}", "", tVal, false},
  	{"bug14b", "{{$x := nil}}{{$x.anything}}", "", tVal, false},
  	{"bug14c", `{{$x := (1.0)}}{{$y := ("hello")}}{{$x.anything}}{{$y.true}}`, "", tVal, false},
  	// Didn't call validateType on function results. Issue 10800.
  	{"bug15", "{{valueString returnInt}}", "", tVal, false},
  	// Variadic function corner cases. Issue 10946.
  	{"bug16a", "{{true|printf}}", "", tVal, false},
  	{"bug16b", "{{1|printf}}", "", tVal, false},
  	{"bug16c", "{{1.1|printf}}", "", tVal, false},
  	{"bug16d", "{{'x'|printf}}", "", tVal, false},
  	{"bug16e", "{{0i|printf}}", "", tVal, false},
  	{"bug16f", "{{true|twoArgs \"xxx\"}}", "", tVal, false},
  	{"bug16g", "{{\"aaa\" |twoArgs \"bbb\"}}", "twoArgs=bbbaaa", tVal, true},
  	{"bug16h", "{{1|oneArg}}", "", tVal, false},
  	{"bug16i", "{{\"aaa\"|oneArg}}", "oneArg=aaa", tVal, true},
  	{"bug16j", "{{1+2i|printf \"%v\"}}", "(1+2i)", tVal, true},
  	{"bug16k", "{{\"aaa\"|printf }}", "aaa", tVal, true},
  	{"bug17a", "{{.NonEmptyInterface.X}}", "x", tVal, true},
  	{"bug17b", "-{{.NonEmptyInterface.Method1 1234}}-", "-1234-", tVal, true},
  	{"bug17c", "{{len .NonEmptyInterfacePtS}}", "2", tVal, true},
  	{"bug17d", "{{index .NonEmptyInterfacePtS 0}}", "a", tVal, true},
  	{"bug17e", "{{range .NonEmptyInterfacePtS}}-{{.}}-{{end}}", "-a--b-", tVal, true},
  }
  
  func zeroArgs() string {
  	return "zeroArgs"
  }
  
  func oneArg(a string) string {
  	return "oneArg=" + a
  }
  
  func twoArgs(a, b string) string {
  	return "twoArgs=" + a + b
  }
  
  func dddArg(a int, b ...string) string {
  	return fmt.Sprintln(a, b)
  }
  
  // count returns a channel that will deliver n sequential 1-letter strings starting at "a"
  func count(n int) chan string {
  	if n == 0 {
  		return nil
  	}
  	c := make(chan string)
  	go func() {
  		for i := 0; i < n; i++ {
  			c <- "abcdefghijklmnop"[i : i+1]
  		}
  		close(c)
  	}()
  	return c
  }
  
  // vfunc takes a *V and a V
  func vfunc(V, *V) string {
  	return "vfunc"
  }
  
  // valueString takes a string, not a pointer.
  func valueString(v string) string {
  	return "value is ignored"
  }
  
  // returnInt returns an int
  func returnInt() int {
  	return 7
  }
  
  func add(args ...int) int {
  	sum := 0
  	for _, x := range args {
  		sum += x
  	}
  	return sum
  }
  
  func echo(arg interface{}) interface{} {
  	return arg
  }
  
  func makemap(arg ...string) map[string]string {
  	if len(arg)%2 != 0 {
  		panic("bad makemap")
  	}
  	m := make(map[string]string)
  	for i := 0; i < len(arg); i += 2 {
  		m[arg[i]] = arg[i+1]
  	}
  	return m
  }
  
  func stringer(s fmt.Stringer) string {
  	return s.String()
  }
  
  func mapOfThree() interface{} {
  	return map[string]int{"three": 3}
  }
  
  func testExecute(execTests []execTest, template *Template, t *testing.T) {
  	b := new(bytes.Buffer)
  	funcs := FuncMap{
  		"add":         add,
  		"count":       count,
  		"dddArg":      dddArg,
  		"echo":        echo,
  		"makemap":     makemap,
  		"mapOfThree":  mapOfThree,
  		"oneArg":      oneArg,
  		"returnInt":   returnInt,
  		"stringer":    stringer,
  		"twoArgs":     twoArgs,
  		"typeOf":      typeOf,
  		"valueString": valueString,
  		"vfunc":       vfunc,
  		"zeroArgs":    zeroArgs,
  	}
  	for _, test := range execTests {
  		var tmpl *Template
  		var err error
  		if template == nil {
  			tmpl, err = New(test.name).Funcs(funcs).Parse(test.input)
  		} else {
  			tmpl, err = template.New(test.name).Funcs(funcs).Parse(test.input)
  		}
  		if err != nil {
  			t.Errorf("%s: parse error: %s", test.name, err)
  			continue
  		}
  		b.Reset()
  		err = tmpl.Execute(b, test.data)
  		switch {
  		case !test.ok && err == nil:
  			t.Errorf("%s: expected error; got none", test.name)
  			continue
  		case test.ok && err != nil:
  			t.Errorf("%s: unexpected execute error: %s", test.name, err)
  			continue
  		case !test.ok && err != nil:
  			// expected error, got one
  			if *debug {
  				fmt.Printf("%s: %s\n\t%s\n", test.name, test.input, err)
  			}
  		}
  		result := b.String()
  		if result != test.output {
  			t.Errorf("%s: expected\n\t%q\ngot\n\t%q", test.name, test.output, result)
  		}
  	}
  }
  
  func TestExecute(t *testing.T) {
  	testExecute(execTests, nil, t)
  }
  
  var delimPairs = []string{
  	"", "", // default
  	"{{", "}}", // same as default
  	"<<", ">>", // distinct
  	"|", "|", // same
  	"(日)", "(本)", // peculiar
  }
  
  func TestDelims(t *testing.T) {
  	const hello = "Hello, world"
  	var value = struct{ Str string }{hello}
  	for i := 0; i < len(delimPairs); i += 2 {
  		text := ".Str"
  		left := delimPairs[i+0]
  		trueLeft := left
  		right := delimPairs[i+1]
  		trueRight := right
  		if left == "" { // default case
  			trueLeft = "{{"
  		}
  		if right == "" { // default case
  			trueRight = "}}"
  		}
  		text = trueLeft + text + trueRight
  		// Now add a comment
  		text += trueLeft + "/*comment*/" + trueRight
  		// Now add  an action containing a string.
  		text += trueLeft + `"` + trueLeft + `"` + trueRight
  		// At this point text looks like `{{.Str}}{{/*comment*/}}{{"{{"}}`.
  		tmpl, err := New("delims").Delims(left, right).Parse(text)
  		if err != nil {
  			t.Fatalf("delim %q text %q parse err %s", left, text, err)
  		}
  		var b = new(bytes.Buffer)
  		err = tmpl.Execute(b, value)
  		if err != nil {
  			t.Fatalf("delim %q exec err %s", left, err)
  		}
  		if b.String() != hello+trueLeft {
  			t.Errorf("expected %q got %q", hello+trueLeft, b.String())
  		}
  	}
  }
  
  // Check that an error from a method flows back to the top.
  func TestExecuteError(t *testing.T) {
  	b := new(bytes.Buffer)
  	tmpl := New("error")
  	_, err := tmpl.Parse("{{.MyError true}}")
  	if err != nil {
  		t.Fatalf("parse error: %s", err)
  	}
  	err = tmpl.Execute(b, tVal)
  	if err == nil {
  		t.Errorf("expected error; got none")
  	} else if !strings.Contains(err.Error(), myError.Error()) {
  		if *debug {
  			fmt.Printf("test execute error: %s\n", err)
  		}
  		t.Errorf("expected myError; got %s", err)
  	}
  }
  
  const execErrorText = `line 1
  line 2
  line 3
  {{template "one" .}}
  {{define "one"}}{{template "two" .}}{{end}}
  {{define "two"}}{{template "three" .}}{{end}}
  {{define "three"}}{{index "hi" $}}{{end}}`
  
  // Check that an error from a nested template contains all the relevant information.
  func TestExecError(t *testing.T) {
  	tmpl, err := New("top").Parse(execErrorText)
  	if err != nil {
  		t.Fatal("parse error:", err)
  	}
  	var b bytes.Buffer
  	err = tmpl.Execute(&b, 5) // 5 is out of range indexing "hi"
  	if err == nil {
  		t.Fatal("expected error")
  	}
  	const want = `template: top:7:20: executing "three" at <index "hi" $>: error calling index: index out of range: 5`
  	got := err.Error()
  	if got != want {
  		t.Errorf("expected\n%q\ngot\n%q", want, got)
  	}
  }
  
  func TestJSEscaping(t *testing.T) {
  	testCases := []struct {
  		in, exp string
  	}{
  		{`a`, `a`},
  		{`'foo`, `\'foo`},
  		{`Go "jump" \`, `Go \"jump\" \\`},
  		{`Yukihiro says "今日は世界"`, `Yukihiro says \"今日は世界\"`},
  		{"unprintable \uFDFF", `unprintable \uFDFF`},
  		{`<html>`, `\x3Chtml\x3E`},
  	}
  	for _, tc := range testCases {
  		s := JSEscapeString(tc.in)
  		if s != tc.exp {
  			t.Errorf("JS escaping [%s] got [%s] want [%s]", tc.in, s, tc.exp)
  		}
  	}
  }
  
  // A nice example: walk a binary tree.
  
  type Tree struct {
  	Val         int
  	Left, Right *Tree
  }
  
  // Use different delimiters to test Set.Delims.
  // Also test the trimming of leading and trailing spaces.
  const treeTemplate = `
  	(- define "tree" -)
  	[
  		(- .Val -)
  		(- with .Left -)
  			(template "tree" . -)
  		(- end -)
  		(- with .Right -)
  			(- template "tree" . -)
  		(- end -)
  	]
  	(- end -)
  `
  
  func TestTree(t *testing.T) {
  	var tree = &Tree{
  		1,
  		&Tree{
  			2, &Tree{
  				3,
  				&Tree{
  					4, nil, nil,
  				},
  				nil,
  			},
  			&Tree{
  				5,
  				&Tree{
  					6, nil, nil,
  				},
  				nil,
  			},
  		},
  		&Tree{
  			7,
  			&Tree{
  				8,
  				&Tree{
  					9, nil, nil,
  				},
  				nil,
  			},
  			&Tree{
  				10,
  				&Tree{
  					11, nil, nil,
  				},
  				nil,
  			},
  		},
  	}
  	tmpl, err := New("root").Delims("(", ")").Parse(treeTemplate)
  	if err != nil {
  		t.Fatal("parse error:", err)
  	}
  	var b bytes.Buffer
  	const expect = "[1[2[3[4]][5[6]]][7[8[9]][10[11]]]]"
  	// First by looking up the template.
  	err = tmpl.Lookup("tree").Execute(&b, tree)
  	if err != nil {
  		t.Fatal("exec error:", err)
  	}
  	result := b.String()
  	if result != expect {
  		t.Errorf("expected %q got %q", expect, result)
  	}
  	// Then direct to execution.
  	b.Reset()
  	err = tmpl.ExecuteTemplate(&b, "tree", tree)
  	if err != nil {
  		t.Fatal("exec error:", err)
  	}
  	result = b.String()
  	if result != expect {
  		t.Errorf("expected %q got %q", expect, result)
  	}
  }
  
  func TestExecuteOnNewTemplate(t *testing.T) {
  	// This is issue 3872.
  	New("Name").Templates()
  	// This is issue 11379.
  	new(Template).Templates()
  	new(Template).Parse("")
  	new(Template).New("abc").Parse("")
  	new(Template).Execute(nil, nil)                // returns an error (but does not crash)
  	new(Template).ExecuteTemplate(nil, "XXX", nil) // returns an error (but does not crash)
  }
  
  const testTemplates = `{{define "one"}}one{{end}}{{define "two"}}two{{end}}`
  
  func TestMessageForExecuteEmpty(t *testing.T) {
  	// Test a truly empty template.
  	tmpl := New("empty")
  	var b bytes.Buffer
  	err := tmpl.Execute(&b, 0)
  	if err == nil {
  		t.Fatal("expected initial error")
  	}
  	got := err.Error()
  	want := `template: empty: "empty" is an incomplete or empty template`
  	if got != want {
  		t.Errorf("expected error %s got %s", want, got)
  	}
  	// Add a non-empty template to check that the error is helpful.
  	tests, err := New("").Parse(testTemplates)
  	if err != nil {
  		t.Fatal(err)
  	}
  	tmpl.AddParseTree("secondary", tests.Tree)
  	err = tmpl.Execute(&b, 0)
  	if err == nil {
  		t.Fatal("expected second error")
  	}
  	got = err.Error()
  	want = `template: empty: "empty" is an incomplete or empty template`
  	if got != want {
  		t.Errorf("expected error %s got %s", want, got)
  	}
  	// Make sure we can execute the secondary.
  	err = tmpl.ExecuteTemplate(&b, "secondary", 0)
  	if err != nil {
  		t.Fatal(err)
  	}
  }
  
  func TestFinalForPrintf(t *testing.T) {
  	tmpl, err := New("").Parse(`{{"x" | printf}}`)
  	if err != nil {
  		t.Fatal(err)
  	}
  	var b bytes.Buffer
  	err = tmpl.Execute(&b, 0)
  	if err != nil {
  		t.Fatal(err)
  	}
  }
  
  type cmpTest struct {
  	expr  string
  	truth string
  	ok    bool
  }
  
  var cmpTests = []cmpTest{
  	{"eq true true", "true", true},
  	{"eq true false", "false", true},
  	{"eq 1+2i 1+2i", "true", true},
  	{"eq 1+2i 1+3i", "false", true},
  	{"eq 1.5 1.5", "true", true},
  	{"eq 1.5 2.5", "false", true},
  	{"eq 1 1", "true", true},
  	{"eq 1 2", "false", true},
  	{"eq `xy` `xy`", "true", true},
  	{"eq `xy` `xyz`", "false", true},
  	{"eq .Uthree .Uthree", "true", true},
  	{"eq .Uthree .Ufour", "false", true},
  	{"eq 3 4 5 6 3", "true", true},
  	{"eq 3 4 5 6 7", "false", true},
  	{"ne true true", "false", true},
  	{"ne true false", "true", true},
  	{"ne 1+2i 1+2i", "false", true},
  	{"ne 1+2i 1+3i", "true", true},
  	{"ne 1.5 1.5", "false", true},
  	{"ne 1.5 2.5", "true", true},
  	{"ne 1 1", "false", true},
  	{"ne 1 2", "true", true},
  	{"ne `xy` `xy`", "false", true},
  	{"ne `xy` `xyz`", "true", true},
  	{"ne .Uthree .Uthree", "false", true},
  	{"ne .Uthree .Ufour", "true", true},
  	{"lt 1.5 1.5", "false", true},
  	{"lt 1.5 2.5", "true", true},
  	{"lt 1 1", "false", true},
  	{"lt 1 2", "true", true},
  	{"lt `xy` `xy`", "false", true},
  	{"lt `xy` `xyz`", "true", true},
  	{"lt .Uthree .Uthree", "false", true},
  	{"lt .Uthree .Ufour", "true", true},
  	{"le 1.5 1.5", "true", true},
  	{"le 1.5 2.5", "true", true},
  	{"le 2.5 1.5", "false", true},
  	{"le 1 1", "true", true},
  	{"le 1 2", "true", true},
  	{"le 2 1", "false", true},
  	{"le `xy` `xy`", "true", true},
  	{"le `xy` `xyz`", "true", true},
  	{"le `xyz` `xy`", "false", true},
  	{"le .Uthree .Uthree", "true", true},
  	{"le .Uthree .Ufour", "true", true},
  	{"le .Ufour .Uthree", "false", true},
  	{"gt 1.5 1.5", "false", true},
  	{"gt 1.5 2.5", "false", true},
  	{"gt 1 1", "false", true},
  	{"gt 2 1", "true", true},
  	{"gt 1 2", "false", true},
  	{"gt `xy` `xy`", "false", true},
  	{"gt `xy` `xyz`", "false", true},
  	{"gt .Uthree .Uthree", "false", true},
  	{"gt .Uthree .Ufour", "false", true},
  	{"gt .Ufour .Uthree", "true", true},
  	{"ge 1.5 1.5", "true", true},
  	{"ge 1.5 2.5", "false", true},
  	{"ge 2.5 1.5", "true", true},
  	{"ge 1 1", "true", true},
  	{"ge 1 2", "false", true},
  	{"ge 2 1", "true", true},
  	{"ge `xy` `xy`", "true", true},
  	{"ge `xy` `xyz`", "false", true},
  	{"ge `xyz` `xy`", "true", true},
  	{"ge .Uthree .Uthree", "true", true},
  	{"ge .Uthree .Ufour", "false", true},
  	{"ge .Ufour .Uthree", "true", true},
  	// Mixing signed and unsigned integers.
  	{"eq .Uthree .Three", "true", true},
  	{"eq .Three .Uthree", "true", true},
  	{"le .Uthree .Three", "true", true},
  	{"le .Three .Uthree", "true", true},
  	{"ge .Uthree .Three", "true", true},
  	{"ge .Three .Uthree", "true", true},
  	{"lt .Uthree .Three", "false", true},
  	{"lt .Three .Uthree", "false", true},
  	{"gt .Uthree .Three", "false", true},
  	{"gt .Three .Uthree", "false", true},
  	{"eq .Ufour .Three", "false", true},
  	{"lt .Ufour .Three", "false", true},
  	{"gt .Ufour .Three", "true", true},
  	{"eq .NegOne .Uthree", "false", true},
  	{"eq .Uthree .NegOne", "false", true},
  	{"ne .NegOne .Uthree", "true", true},
  	{"ne .Uthree .NegOne", "true", true},
  	{"lt .NegOne .Uthree", "true", true},
  	{"lt .Uthree .NegOne", "false", true},
  	{"le .NegOne .Uthree", "true", true},
  	{"le .Uthree .NegOne", "false", true},
  	{"gt .NegOne .Uthree", "false", true},
  	{"gt .Uthree .NegOne", "true", true},
  	{"ge .NegOne .Uthree", "false", true},
  	{"ge .Uthree .NegOne", "true", true},
  	{"eq (index `x` 0) 'x'", "true", true}, // The example that triggered this rule.
  	{"eq (index `x` 0) 'y'", "false", true},
  	// Errors
  	{"eq `xy` 1", "", false},    // Different types.
  	{"eq 2 2.0", "", false},     // Different types.
  	{"lt true true", "", false}, // Unordered types.
  	{"lt 1+0i 1+0i", "", false}, // Unordered types.
  }
  
  func TestComparison(t *testing.T) {
  	b := new(bytes.Buffer)
  	var cmpStruct = struct {
  		Uthree, Ufour uint
  		NegOne, Three int
  	}{3, 4, -1, 3}
  	for _, test := range cmpTests {
  		text := fmt.Sprintf("{{if %s}}true{{else}}false{{end}}", test.expr)
  		tmpl, err := New("empty").Parse(text)
  		if err != nil {
  			t.Fatalf("%q: %s", test.expr, err)
  		}
  		b.Reset()
  		err = tmpl.Execute(b, &cmpStruct)
  		if test.ok && err != nil {
  			t.Errorf("%s errored incorrectly: %s", test.expr, err)
  			continue
  		}
  		if !test.ok && err == nil {
  			t.Errorf("%s did not error", test.expr)
  			continue
  		}
  		if b.String() != test.truth {
  			t.Errorf("%s: want %s; got %s", test.expr, test.truth, b.String())
  		}
  	}
  }
  
  func TestMissingMapKey(t *testing.T) {
  	data := map[string]int{
  		"x": 99,
  	}
  	tmpl, err := New("t1").Parse("{{.x}} {{.y}}")
  	if err != nil {
  		t.Fatal(err)
  	}
  	var b bytes.Buffer
  	// By default, just get "<no value>"
  	err = tmpl.Execute(&b, data)
  	if err != nil {
  		t.Fatal(err)
  	}
  	want := "99 <no value>"
  	got := b.String()
  	if got != want {
  		t.Errorf("got %q; expected %q", got, want)
  	}
  	// Same if we set the option explicitly to the default.
  	tmpl.Option("missingkey=default")
  	b.Reset()
  	err = tmpl.Execute(&b, data)
  	if err != nil {
  		t.Fatal("default:", err)
  	}
  	want = "99 <no value>"
  	got = b.String()
  	if got != want {
  		t.Errorf("got %q; expected %q", got, want)
  	}
  	// Next we ask for a zero value
  	tmpl.Option("missingkey=zero")
  	b.Reset()
  	err = tmpl.Execute(&b, data)
  	if err != nil {
  		t.Fatal("zero:", err)
  	}
  	want = "99 0"
  	got = b.String()
  	if got != want {
  		t.Errorf("got %q; expected %q", got, want)
  	}
  	// Now we ask for an error.
  	tmpl.Option("missingkey=error")
  	err = tmpl.Execute(&b, data)
  	if err == nil {
  		t.Errorf("expected error; got none")
  	}
  	// same Option, but now a nil interface: ask for an error
  	err = tmpl.Execute(&b, nil)
  	t.Log(err)
  	if err == nil {
  		t.Errorf("expected error for nil-interface; got none")
  	}
  }
  
  // Test that the error message for multiline unterminated string
  // refers to the line number of the opening quote.
  func TestUnterminatedStringError(t *testing.T) {
  	_, err := New("X").Parse("hello\n\n{{`unterminated\n\n\n\n}}\n some more\n\n")
  	if err == nil {
  		t.Fatal("expected error")
  	}
  	str := err.Error()
  	if !strings.Contains(str, "X:3: unexpected unterminated raw quoted string") {
  		t.Fatalf("unexpected error: %s", str)
  	}
  }
  
  const alwaysErrorText = "always be failing"
  
  var alwaysError = errors.New(alwaysErrorText)
  
  type ErrorWriter int
  
  func (e ErrorWriter) Write(p []byte) (int, error) {
  	return 0, alwaysError
  }
  
  func TestExecuteGivesExecError(t *testing.T) {
  	// First, a non-execution error shouldn't be an ExecError.
  	tmpl, err := New("X").Parse("hello")
  	if err != nil {
  		t.Fatal(err)
  	}
  	err = tmpl.Execute(ErrorWriter(0), 0)
  	if err == nil {
  		t.Fatal("expected error; got none")
  	}
  	if err.Error() != alwaysErrorText {
  		t.Errorf("expected %q error; got %q", alwaysErrorText, err)
  	}
  	// This one should be an ExecError.
  	tmpl, err = New("X").Parse("hello, {{.X.Y}}")
  	if err != nil {
  		t.Fatal(err)
  	}
  	err = tmpl.Execute(ioutil.Discard, 0)
  	if err == nil {
  		t.Fatal("expected error; got none")
  	}
  	eerr, ok := err.(ExecError)
  	if !ok {
  		t.Fatalf("did not expect ExecError %s", eerr)
  	}
  	expect := "field X in type int"
  	if !strings.Contains(err.Error(), expect) {
  		t.Errorf("expected %q; got %q", expect, err)
  	}
  }
  
  func funcNameTestFunc() int {
  	return 0
  }
  
  func TestGoodFuncNames(t *testing.T) {
  	names := []string{
  		"_",
  		"a",
  		"a1",
  		"a1",
  		"Ӵ",
  	}
  	for _, name := range names {
  		tmpl := New("X").Funcs(
  			FuncMap{
  				name: funcNameTestFunc,
  			},
  		)
  		if tmpl == nil {
  			t.Fatalf("nil result for %q", name)
  		}
  	}
  }
  
  func TestBadFuncNames(t *testing.T) {
  	names := []string{
  		"",
  		"2",
  		"a-b",
  	}
  	for _, name := range names {
  		testBadFuncName(name, t)
  	}
  }
  
  func testBadFuncName(name string, t *testing.T) {
  	defer func() {
  		recover()
  	}()
  	New("X").Funcs(
  		FuncMap{
  			name: funcNameTestFunc,
  		},
  	)
  	// If we get here, the name did not cause a panic, which is how Funcs
  	// reports an error.
  	t.Errorf("%q succeeded incorrectly as function name", name)
  }
  
  func TestBlock(t *testing.T) {
  	const (
  		input   = `a({{block "inner" .}}bar({{.}})baz{{end}})b`
  		want    = `a(bar(hello)baz)b`
  		overlay = `{{define "inner"}}foo({{.}})bar{{end}}`
  		want2   = `a(foo(goodbye)bar)b`
  	)
  	tmpl, err := New("outer").Parse(input)
  	if err != nil {
  		t.Fatal(err)
  	}
  	tmpl2, err := Must(tmpl.Clone()).Parse(overlay)
  	if err != nil {
  		t.Fatal(err)
  	}
  
  	var buf bytes.Buffer
  	if err := tmpl.Execute(&buf, "hello"); err != nil {
  		t.Fatal(err)
  	}
  	if got := buf.String(); got != want {
  		t.Errorf("got %q, want %q", got, want)
  	}
  
  	buf.Reset()
  	if err := tmpl2.Execute(&buf, "goodbye"); err != nil {
  		t.Fatal(err)
  	}
  	if got := buf.String(); got != want2 {
  		t.Errorf("got %q, want %q", got, want2)
  	}
  }
  
  // Check that calling an invalid field on nil pointer prints
  // a field error instead of a distracting nil pointer error.
  // https://golang.org/issue/15125
  func TestMissingFieldOnNil(t *testing.T) {
  	tmpl := Must(New("tmpl").Parse("{{.MissingField}}"))
  	var d *T
  	err := tmpl.Execute(ioutil.Discard, d)
  	got := "<nil>"
  	if err != nil {
  		got = err.Error()
  	}
  	want := "can't evaluate field MissingField in type *template.T"
  	if !strings.HasSuffix(got, want) {
  		t.Errorf("got error %q, want %q", got, want)
  	}
  }
  
  func TestMaxExecDepth(t *testing.T) {
  	tmpl := Must(New("tmpl").Parse(`{{template "tmpl" .}}`))
  	err := tmpl.Execute(ioutil.Discard, nil)
  	got := "<nil>"
  	if err != nil {
  		got = err.Error()
  	}
  	const want = "exceeded maximum template depth"
  	if !strings.Contains(got, want) {
  		t.Errorf("got error %q; want %q", got, want)
  	}
  }
  
  func TestAddrOfIndex(t *testing.T) {
  	// golang.org/issue/14916.
  	// Before index worked on reflect.Values, the .String could not be
  	// found on the (incorrectly unaddressable) V value,
  	// in contrast to range, which worked fine.
  	// Also testing that passing a reflect.Value to tmpl.Execute works.
  	texts := []string{
  		`{{range .}}{{.String}}{{end}}`,
  		`{{with index . 0}}{{.String}}{{end}}`,
  	}
  	for _, text := range texts {
  		tmpl := Must(New("tmpl").Parse(text))
  		var buf bytes.Buffer
  		err := tmpl.Execute(&buf, reflect.ValueOf([]V{{1}}))
  		if err != nil {
  			t.Fatalf("%s: Execute: %v", text, err)
  		}
  		if buf.String() != "<1>" {
  			t.Fatalf("%s: template output = %q, want %q", text, &buf, "<1>")
  		}
  	}
  }
  
  func TestInterfaceValues(t *testing.T) {
  	// golang.org/issue/17714.
  	// Before index worked on reflect.Values, interface values
  	// were always implicitly promoted to the underlying value,
  	// except that nil interfaces were promoted to the zero reflect.Value.
  	// Eliminating a round trip to interface{} and back to reflect.Value
  	// eliminated this promotion, breaking these cases.
  	tests := []struct {
  		text string
  		out  string
  	}{
  		{`{{index .Nil 1}}`, "ERROR: index of untyped nil"},
  		{`{{index .Slice 2}}`, "2"},
  		{`{{index .Slice .Two}}`, "2"},
  		{`{{call .Nil 1}}`, "ERROR: call of nil"},
  		{`{{call .PlusOne 1}}`, "2"},
  		{`{{call .PlusOne .One}}`, "2"},
  		{`{{and (index .Slice 0) true}}`, "0"},
  		{`{{and .Zero true}}`, "0"},
  		{`{{and (index .Slice 1) false}}`, "false"},
  		{`{{and .One false}}`, "false"},
  		{`{{or (index .Slice 0) false}}`, "false"},
  		{`{{or .Zero false}}`, "false"},
  		{`{{or (index .Slice 1) true}}`, "1"},
  		{`{{or .One true}}`, "1"},
  		{`{{not (index .Slice 0)}}`, "true"},
  		{`{{not .Zero}}`, "true"},
  		{`{{not (index .Slice 1)}}`, "false"},
  		{`{{not .One}}`, "false"},
  		{`{{eq (index .Slice 0) .Zero}}`, "true"},
  		{`{{eq (index .Slice 1) .One}}`, "true"},
  		{`{{ne (index .Slice 0) .Zero}}`, "false"},
  		{`{{ne (index .Slice 1) .One}}`, "false"},
  		{`{{ge (index .Slice 0) .One}}`, "false"},
  		{`{{ge (index .Slice 1) .Zero}}`, "true"},
  		{`{{gt (index .Slice 0) .One}}`, "false"},
  		{`{{gt (index .Slice 1) .Zero}}`, "true"},
  		{`{{le (index .Slice 0) .One}}`, "true"},
  		{`{{le (index .Slice 1) .Zero}}`, "false"},
  		{`{{lt (index .Slice 0) .One}}`, "true"},
  		{`{{lt (index .Slice 1) .Zero}}`, "false"},
  	}
  
  	for _, tt := range tests {
  		tmpl := Must(New("tmpl").Parse(tt.text))
  		var buf bytes.Buffer
  		err := tmpl.Execute(&buf, map[string]interface{}{
  			"PlusOne": func(n int) int {
  				return n + 1
  			},
  			"Slice": []int{0, 1, 2, 3},
  			"One":   1,
  			"Two":   2,
  			"Nil":   nil,
  			"Zero":  0,
  		})
  		if strings.HasPrefix(tt.out, "ERROR:") {
  			e := strings.TrimSpace(strings.TrimPrefix(tt.out, "ERROR:"))
  			if err == nil || !strings.Contains(err.Error(), e) {
  				t.Errorf("%s: Execute: %v, want error %q", tt.text, err, e)
  			}
  			continue
  		}
  		if err != nil {
  			t.Errorf("%s: Execute: %v", tt.text, err)
  			continue
  		}
  		if buf.String() != tt.out {
  			t.Errorf("%s: template output = %q, want %q", tt.text, &buf, tt.out)
  		}
  	}
  }
  

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