html/template: add tests from text/template

Copy and adapt tests from text/template, to exercise more of html/template's copy.

Various differences in behavior are flagged with NOTE comments or t.Skip
and documented in #40075. Many of them are probably bugs.
One clarifying test case added to both text/template and html/template.

No changes to the package itself.

Change-Id: Ifefad83d647db846040d24c2741a0244b00ade82
Reviewed-on: https://go-review.googlesource.com/c/go/+/241084
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

10 files changed, 1970 insertions, 5 deletions

diff --git a/src/html/template/clone_test.go b/src/html/template/clone_test.go
index e292321d93..c9c619f0d4 100644
--- a/src/html/template/clone_test.go
+++ b/src/html/template/clone_test.go
@@ -15,7 +15,7 @@ import (
 	"text/template/parse"
 )
 
-func TestAddParseTree(t *testing.T) {
+func TestAddParseTreeHTML(t *testing.T) {
 	root := Must(New("root").Parse(`{{define "a"}} {{.}} {{template "b"}} {{.}} "></a>{{end}}`))
 	tree, err := parse.Parse("t", `{{define "b"}}<a href="{{end}}`, "", "", nil, nil)
 	if err != nil {
diff --git a/src/html/template/content_test.go b/src/html/template/content_test.go
index bd8652769b..b7a39d4814 100644
--- a/src/html/template/content_test.go
+++ b/src/html/template/content_test.go
@@ -401,11 +401,11 @@ func TestTypedContent(t *testing.T) {
 }
 
 // Test that we print using the String method. Was issue 3073.
-type stringer struct {
+type myStringer struct {
 	v int
 }
 
-func (s *stringer) String() string {
+func (s *myStringer) String() string {
 	return fmt.Sprintf("string=%d", s.v)
 }
 
@@ -418,7 +418,7 @@ func (s *errorer) Error() string {
 }
 
 func TestStringer(t *testing.T) {
-	s := &stringer{3}
+	s := &myStringer{3}
 	b := new(bytes.Buffer)
 	tmpl := Must(New("x").Parse("{{.}}"))
 	if err := tmpl.Execute(b, s); err != nil {
diff --git a/src/html/template/escape_test.go b/src/html/template/escape_test.go
index c709660f06..fbc84a7592 100644
--- a/src/html/template/escape_test.go
+++ b/src/html/template/escape_test.go
@@ -1821,7 +1821,7 @@ func TestIndirectPrint(t *testing.T) {
 }
 
 // This is a test for issue 3272.
-func TestEmptyTemplate(t *testing.T) {
+func TestEmptyTemplateHTML(t *testing.T) {
 	page := Must(New("page").ParseFiles(os.DevNull))
 	if err := page.ExecuteTemplate(os.Stdout, "page", "nothing"); err == nil {
 		t.Fatal("expected error")
diff --git a/src/html/template/exec_test.go b/src/html/template/exec_test.go
new file mode 100644
index 0000000000..ec2bfcccab
--- /dev/null
+++ b/src/html/template/exec_test.go
@@ -0,0 +1,1708 @@
+// 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.
+
+// Tests for template execution, copied from text/template.
+
+package template
+
+import (
+	"bytes"
+	"errors"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"reflect"
+	"strings"
+	"testing"
+	"text/template"
+)
+
+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, S        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
+	SICap   []int
+	SIEmpty []int
+	SB      []bool
+	// Arrays
+	AI [3]int
+	// 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
+	MI32S    map[int32]string
+	MI64S    map[int64]string
+	MUI32S   map[uint32]string
+	MUI64S   map[uint64]string
+	MI8S     map[int8]string
+	MUI8S    map[uint8]string
+	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
+	NonEmptyInterfaceNil      I
+	NonEmptyInterfaceTypedNil 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)
+	PanicFunc       func() string
+	// 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",
+	S:      "xyz",
+	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},
+	SICap:  make([]int, 5, 10),
+	AI:     [3]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},
+	MI32S:  map[int32]string{1: "one", 2: "two"},
+	MI64S:  map[int64]string{2: "i642", 3: "i643"},
+	MUI32S: map[uint32]string{2: "u322", 3: "u323"},
+	MUI64S: map[uint64]string{2: "ui642", 3: "ui643"},
+	MI8S:   map[int8]string{2: "i82", 3: "i83"},
+	MUI8S:  map[uint8]string{2: "u82", 3: "u83"},
+	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,
+	NonEmptyInterfaceTypedNil: (*T)(nil),
+	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 },
+	PanicFunc:                 func() string { panic("test panic") },
+	Tmpl:                      Must(New("x").Parse("test template")), // "x" is the value of .X
+}
+
+var tSliceOfNil = []*T{nil}
+
+// 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}}", "", tVal, true}, // NOTE: <no value> in text/template
+	{"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", "<{{.}}>", "&lt;13>", 13, true},
+	{"dot uint", "<{{.}}>", "&lt;14>", uint(14), true},
+	{"dot float", "<{{.}}>", "&lt;15.1>", 15.1, true},
+	{"dot bool", "<{{.}}>", "&lt;true>", true, true},
+	{"dot complex", "<{{.}}>", "&lt;(16.2-17i)>", 16.2 - 17i, true},
+	{"dot string", "<{{.}}>", "&lt;hello>", "hello", true},
+	{"dot slice", "<{{.}}>", "&lt;[-1 -2 -3]>", []int{-1, -2, -3}, true},
+	{"dot map", "<{{.}}>", "&lt;map[two:22]>", map[string]int{"two": 22}, true},
+	{"dot struct", "<{{.}}>", "&lt;{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},
+	{"simple assignment", "{{$x := 2}}{{$x = 3}}{{$x}}", "3", tVal, true},
+	{"nested assignment",
+		"{{$x := 2}}{{if true}}{{$x = 3}}{{end}}{{$x}}",
+		"3", tVal, true},
+	{"nested assignment changes the last declaration",
+		"{{$x := 1}}{{if true}}{{$x := 2}}{{if true}}{{$x = 3}}{{end}}{{end}}{{$x}}",
+		"1", tVal, true},
+
+	// Type with String method.
+	{"V{6666}.String()", "-{{.V0}}-", "-{6666}-", tVal, true}, //  NOTE: -<6666>- in text/template
+	{"&V{7777}.String()", "-{{.V1}}-", "-&lt;7777&gt;-", tVal, true},
+	{"(*V)(nil).String()", "-{{.V2}}-", "-nilV-", tVal, true},
+
+	// Type with Error method.
+	{"W{888}.Error()", "-{{.W0}}-", "-{888}-", tVal, true}, // NOTE: -[888] in text/template
+	{"&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}}", "&lt;nil&gt;", tVal, true},
+
+	// Empty interfaces holding values.
+	{"empty nil", "{{.Empty0}}", "", tVal, true}, // NOTE: <no value> in text/template
+	{"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},
+
+	// Edge cases with <no value> with an interface value
+	{"field on interface", "{{.foo}}", "", nil, true},                  // NOTE: <no value> in text/template
+	{"field on parenthesized interface", "{{(.).foo}}", "", nil, true}, // NOTE: <no value> in text/template
+
+	// Issue 31810: Parenthesized first element of pipeline with arguments.
+	// See also TestIssue31810.
+	{"unparenthesized non-function", "{{1 2}}", "", nil, false},
+	{"parenthesized non-function", "{{(1) 2}}", "", nil, false},
+	{"parenthesized non-function with no args", "{{(1)}}", "1", nil, true}, // This is fine.
+
+	// 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: &lt;nil&gt;-", tVal, true},
+	{".Method3(nil value)", "-{{.Method3 .MXI.unset}}-", "-Method3: &lt;nil&gt;-", 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},
+	{"method on nil value from slice", "-{{range .}}{{.Method1 1234}}{{end}}-", "-1234-", tSliceOfNil, true},
+	{"method on typed nil interface value", "{{.NonEmptyInterfaceTypedNil.Method0}}", "M0", tVal, true},
+
+	// Function call builtin.
+	{".BinaryFunc", "{{call .BinaryFunc `1` `2`}}", "[1=2]", tVal, true},
+	{".VariadicFunc0", "{{call .VariadicFunc}}", "&lt;&gt;", tVal, true},
+	{".VariadicFunc2", "{{call .VariadicFunc `he` `llo`}}", "&lt;he&#43;llo&gt;", tVal, true},
+	{".VariadicFuncInt", "{{call .VariadicFuncInt 33 `he` `llo`}}", "33=&lt;he&#43;llo&gt;", 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` }}-", "-&lt;he&#43;&lt;llo&gt;&gt;-", tVal, true},
+
+	// Nil values aren't missing arguments.
+	{"nil pipeline", "{{ .Empty0 | call .NilOKFunc }}", "true", tVal, true},
+	{"nil call arg", "{{ call .NilOKFunc .Empty0 }}", "true", tVal, true},
+	{"bad nil pipeline", "{{ .Empty0 | .VariadicFunc }}", "", tVal, false},
+
+	// 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 on typed nil interface value", "{{if .NonEmptyInterfaceTypedNil}}TRUE{{ end }}", "", tVal, true},
+	{"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}}`, "&lt;nil&gt;", 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&#43;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},
+	{"html typed nil", `{{html .NIL}}`, "&lt;nil&gt;", tVal, true},
+	{"html untyped nil", `{{html .Empty0}}`, "&lt;nil&gt;", tVal, true}, // NOTE: "&lt;no value&gt;" in text/template
+
+	// JavaScript.
+	{"js", `{{js .}}`, `It\&#39;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},
+	{"map MI64S", "{{index .MI64S 2}}", "i642", tVal, true},
+	{"map MI32S", "{{index .MI32S 2}}", "two", tVal, true},
+	{"map MUI64S", "{{index .MUI64S 3}}", "ui643", tVal, true},
+	{"map MI8S", "{{index .MI8S 3}}", "i83", tVal, true},
+	{"map MUI8S", "{{index .MUI8S 2}}", "u82", tVal, true},
+	{"index of an interface field", "{{index .Empty3 0}}", "7", tVal, true},
+
+	// Slicing.
+	{"slice[:]", "{{slice .SI}}", "[3 4 5]", tVal, true},
+	{"slice[1:]", "{{slice .SI 1}}", "[4 5]", tVal, true},
+	{"slice[1:2]", "{{slice .SI 1 2}}", "[4]", tVal, true},
+	{"slice[-1:]", "{{slice .SI -1}}", "", tVal, false},
+	{"slice[1:-2]", "{{slice .SI 1 -2}}", "", tVal, false},
+	{"slice[1:2:-1]", "{{slice .SI 1 2 -1}}", "", tVal, false},
+	{"slice[2:1]", "{{slice .SI 2 1}}", "", tVal, false},
+	{"slice[2:2:1]", "{{slice .SI 2 2 1}}", "", tVal, false},
+	{"out of range", "{{slice .SI 4 5}}", "", tVal, false},
+	{"out of range", "{{slice .SI 2 2 5}}", "", tVal, false},
+	{"len(s) < indexes < cap(s)", "{{slice .SICap 6 10}}", "[0 0 0 0]", tVal, true},
+	{"len(s) < indexes < cap(s)", "{{slice .SICap 6 10 10}}", "[0 0 0 0]", tVal, true},
+	{"indexes > cap(s)", "{{slice .SICap 10 11}}", "", tVal, false},
+	{"indexes > cap(s)", "{{slice .SICap 6 10 11}}", "", tVal, false},
+	{"array[:]", "{{slice .AI}}", "[3 4 5]", tVal, true},
+	{"array[1:]", "{{slice .AI 1}}", "[4 5]", tVal, true},
+	{"array[1:2]", "{{slice .AI 1 2}}", "[4]", tVal, true},
+	{"string[:]", "{{slice .S}}", "xyz", tVal, true},
+	{"string[0:1]", "{{slice .S 0 1}}", "x", tVal, true},
+	{"string[1:]", "{{slice .S 1}}", "yz", tVal, true},
+	{"string[1:2]", "{{slice .S 1 2}}", "y", tVal, true},
+	{"out of range", "{{slice .S 1 5}}", "", tVal, false},
+	{"3-index slice of string", "{{slice .S 1 2 2}}", "", tVal, false},
+	{"slice of an interface field", "{{slice .Empty3 0 1}}", "[7]", tVal, true},
+
+	// 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},
+	{"len of an interface field", "{{len .Empty3}}", "2", tVal, true},
+
+	// 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&#43;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},
+	{"with on typed nil interface value", "{{with .NonEmptyInterfaceTypedNil}}TRUE{{ end }}", "", 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}}", "&lt;3>&lt;4>&lt;5>", tVal, true},
+	{"range $x $y SI", "{{range $x, $y := .SI}}<{{$x}}={{$y}}>{{end}}", "&lt;0=3>&lt;1=4>&lt;2=5>", tVal, true},
+	{"range $x MSIone", "{{range $x := .MSIone}}<{{$x}}>{{end}}", "&lt;1>", tVal, true},
+	{"range $x $y MSIone", "{{range $x, $y := .MSIone}}<{{$x}}={{$y}}>{{end}}", "&lt;one=1>", tVal, true},
+	{"range $x PSI", "{{range $x := .PSI}}<{{$x}}>{{end}}", "&lt;21>&lt;22>&lt;23>", tVal, true},
+	{"declare in range", "{{range $x := .PSI}}<{{$foo:=$x}}{{$x}}>{{end}}", "&lt;21>&lt;22>&lt;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},
+
+	// Numbers
+	{"decimal", "{{print 1234}}", "1234", tVal, true},
+	{"decimal _", "{{print 12_34}}", "1234", tVal, true},
+	{"binary", "{{print 0b101}}", "5", tVal, true},
+	{"binary _", "{{print 0b_1_0_1}}", "5", tVal, true},
+	{"BINARY", "{{print 0B101}}", "5", tVal, true},
+	{"octal0", "{{print 0377}}", "255", tVal, true},
+	{"octal", "{{print 0o377}}", "255", tVal, true},
+	{"octal _", "{{print 0o_3_7_7}}", "255", tVal, true},
+	{"OCTAL", "{{print 0O377}}", "255", tVal, true},
+	{"hex", "{{print 0x123}}", "291", tVal, true},
+	{"hex _", "{{print 0x1_23}}", "291", tVal, true},
+	{"HEX", "{{print 0X123ABC}}", "1194684", tVal, true},
+	{"float", "{{print 123.4}}", "123.4", tVal, true},
+	{"float _", "{{print 0_0_1_2_3.4}}", "123.4", tVal, true},
+	{"hex float", "{{print +0x1.ep+2}}", "7.5", tVal, true},
+	{"hex float _", "{{print +0x_1.e_0p+0_2}}", "7.5", tVal, true},
+	{"HEX float", "{{print +0X1.EP+2}}", "7.5", tVal, true},
+	{"print multi", "{{print 1_2_3_4 7.5_00_00_00}}", "1234 7.5", tVal, true},
+	{"print multi2", "{{print 1234 0x0_1.e_0p+02}}", "1234 7.5", 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&#43;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},
+
+	// More variadic function corner cases. Some runes would get evaluated
+	// as constant floats instead of ints. Issue 34483.
+	{"bug18a", "{{eq . '.'}}", "true", '.', true},
+	{"bug18b", "{{eq . 'e'}}", "true", 'e', true},
+	{"bug18c", "{{eq . 'P'}}", "true", 'P', 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.Clone()
+			if err != nil {
+				t.Errorf("%s: clone error: %s", test.name, err)
+				continue
+			}
+			tmpl, err = tmpl.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
+	"|", "|", // 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>`, `\u003Chtml\u003E`},
+		{`no = in attributes`, `no \u003D in attributes`},
+		{`&#x27; does not become HTML entity`, `\u0026#x27; does not become HTML entity`},
+	}
+	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() // TODO: crashes
+	// new(Template).Parse("") // TODO: crashes
+	// new(Template).New("abc").Parse("") // TODO: crashes
+	// new(Template).Execute(nil, nil)                // TODO: crashes; returns an error (but does not crash)
+	// new(Template).ExecuteTemplate(nil, "XXX", nil) // TODO: crashes; 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" is an incomplete or empty template` // NOTE: text/template has extra "empty: " in message
+	if got != want {
+		t.Errorf("expected error %s got %s", want, got)
+	}
+
+	// Add a non-empty template to check that the error is helpful.
+	tmpl = New("empty")
+	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()
+	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},
+	{"eq .V1 .V2", "true", true},
+	{"eq .Ptr .Ptr", "true", true},
+	{"eq .Ptr .NilPtr", "false", true},
+	{"eq .NilPtr .NilPtr", "true", true},
+	{"eq .Iface1 .Iface1", "true", true},
+	{"eq .Iface1 .Iface2", "false", true},
+	{"eq .Iface2 .Iface2", "true", 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.
+	{"eq .Ptr 1", "", false},       // Incompatible types.
+	{"eq .Ptr .NegOne", "", false}, // Incompatible types.
+	{"eq .Map .Map", "", false},    // Uncomparable types.
+	{"eq .Map .V1", "", false},     // Uncomparable types.
+}
+
+func TestComparison(t *testing.T) {
+	b := new(bytes.Buffer)
+	var cmpStruct = struct {
+		Uthree, Ufour  uint
+		NegOne, Three  int
+		Ptr, NilPtr    *int
+		Map            map[int]int
+		V1, V2         V
+		Iface1, Iface2 fmt.Stringer
+	}{
+		Uthree: 3,
+		Ufour:  4,
+		NegOne: -1,
+		Three:  3,
+		Ptr:    new(int),
+		Iface1: b,
+	}
+	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>" // NOTE: not in html/template, get empty string
+	err = tmpl.Execute(&b, data)
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := "99 "
+	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)
+	}
+	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.(template.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) {
+	t.Helper()
+	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)
+	}
+}
+
+func TestEvalFieldErrors(t *testing.T) {
+	tests := []struct {
+		name, src string
+		value     interface{}
+		want      string
+	}{
+		{
+			// 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
+			"MissingFieldOnNil",
+			"{{.MissingField}}",
+			(*T)(nil),
+			"can't evaluate field MissingField in type *template.T",
+		},
+		{
+			"MissingFieldOnNonNil",
+			"{{.MissingField}}",
+			&T{},
+			"can't evaluate field MissingField in type *template.T",
+		},
+		{
+			"ExistingFieldOnNil",
+			"{{.X}}",
+			(*T)(nil),
+			"nil pointer evaluating *template.T.X",
+		},
+		{
+			"MissingKeyOnNilMap",
+			"{{.MissingKey}}",
+			(*map[string]string)(nil),
+			"nil pointer evaluating *map[string]string.MissingKey",
+		},
+		{
+			"MissingKeyOnNilMapPtr",
+			"{{.MissingKey}}",
+			(*map[string]string)(nil),
+			"nil pointer evaluating *map[string]string.MissingKey",
+		},
+		{
+			"MissingKeyOnMapPtrToNil",
+			"{{.MissingKey}}",
+			&map[string]string{},
+			"<nil>",
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			tmpl := Must(New("tmpl").Parse(tc.src))
+			err := tmpl.Execute(ioutil.Discard, tc.value)
+			got := "<nil>"
+			if err != nil {
+				got = err.Error()
+			}
+			if !strings.HasSuffix(got, tc.want) {
+				t.Fatalf("got error %q, want %q", got, tc.want)
+			}
+		})
+	}
+}
+
+func TestMaxExecDepth(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping in -short mode")
+	}
+	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() != "&lt;1&gt;" {
+			t.Fatalf("%s: template output = %q, want %q", text, &buf, "&lt;1&gt;")
+		}
+	}
+}
+
+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)
+		}
+	}
+}
+
+// Check that panics during calls are recovered and returned as errors.
+func TestExecutePanicDuringCall(t *testing.T) {
+	funcs := map[string]interface{}{
+		"doPanic": func() string {
+			panic("custom panic string")
+		},
+	}
+	tests := []struct {
+		name    string
+		input   string
+		data    interface{}
+		wantErr string
+	}{
+		{
+			"direct func call panics",
+			"{{doPanic}}", (*T)(nil),
+			`template: t:1:2: executing "t" at <doPanic>: error calling doPanic: custom panic string`,
+		},
+		{
+			"indirect func call panics",
+			"{{call doPanic}}", (*T)(nil),
+			`template: t:1:7: executing "t" at <doPanic>: error calling doPanic: custom panic string`,
+		},
+		{
+			"direct method call panics",
+			"{{.GetU}}", (*T)(nil),
+			`template: t:1:2: executing "t" at <.GetU>: error calling GetU: runtime error: invalid memory address or nil pointer dereference`,
+		},
+		{
+			"indirect method call panics",
+			"{{call .GetU}}", (*T)(nil),
+			`template: t:1:7: executing "t" at <.GetU>: error calling GetU: runtime error: invalid memory address or nil pointer dereference`,
+		},
+		{
+			"func field call panics",
+			"{{call .PanicFunc}}", tVal,
+			`template: t:1:2: executing "t" at <call .PanicFunc>: error calling call: test panic`,
+		},
+		{
+			"method call on nil interface",
+			"{{.NonEmptyInterfaceNil.Method0}}", tVal,
+			`template: t:1:23: executing "t" at <.NonEmptyInterfaceNil.Method0>: nil pointer evaluating template.I.Method0`,
+		},
+	}
+	for _, tc := range tests {
+		b := new(bytes.Buffer)
+		tmpl, err := New("t").Funcs(funcs).Parse(tc.input)
+		if err != nil {
+			t.Fatalf("parse error: %s", err)
+		}
+		err = tmpl.Execute(b, tc.data)
+		if err == nil {
+			t.Errorf("%s: expected error; got none", tc.name)
+		} else if !strings.Contains(err.Error(), tc.wantErr) {
+			if *debug {
+				fmt.Printf("%s: test execute error: %s\n", tc.name, err)
+			}
+			t.Errorf("%s: expected error:\n%s\ngot:\n%s", tc.name, tc.wantErr, err)
+		}
+	}
+}
+
+// Issue 31810. Check that a parenthesized first argument behaves properly.
+func TestIssue31810(t *testing.T) {
+	t.Skip("broken in html/template")
+
+	// A simple value with no arguments is fine.
+	var b bytes.Buffer
+	const text = "{{ (.)  }}"
+	tmpl, err := New("").Parse(text)
+	if err != nil {
+		t.Error(err)
+	}
+	err = tmpl.Execute(&b, "result")
+	if err != nil {
+		t.Error(err)
+	}
+	if b.String() != "result" {
+		t.Errorf("%s got %q, expected %q", text, b.String(), "result")
+	}
+
+	// Even a plain function fails - need to use call.
+	f := func() string { return "result" }
+	b.Reset()
+	err = tmpl.Execute(&b, f)
+	if err == nil {
+		t.Error("expected error with no call, got none")
+	}
+
+	// Works if the function is explicitly called.
+	const textCall = "{{ (call .)  }}"
+	tmpl, err = New("").Parse(textCall)
+	b.Reset()
+	err = tmpl.Execute(&b, f)
+	if err != nil {
+		t.Error(err)
+	}
+	if b.String() != "result" {
+		t.Errorf("%s got %q, expected %q", textCall, b.String(), "result")
+	}
+}
diff --git a/src/html/template/multi_test.go b/src/html/template/multi_test.go
new file mode 100644
index 0000000000..50526c5b65
--- /dev/null
+++ b/src/html/template/multi_test.go
@@ -0,0 +1,246 @@
+// 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.
+
+// Tests for multiple-template execution, copied from text/template.
+
+package template
+
+import (
+	"bytes"
+	"testing"
+	"text/template/parse"
+)
+
+var multiExecTests = []execTest{
+	{"empty", "", "", nil, true},
+	{"text", "some text", "some text", nil, true},
+	{"invoke x", `{{template "x" .SI}}`, "TEXT", tVal, true},
+	{"invoke x no args", `{{template "x"}}`, "TEXT", tVal, true},
+	{"invoke dot int", `{{template "dot" .I}}`, "17", tVal, true},
+	{"invoke dot []int", `{{template "dot" .SI}}`, "[3 4 5]", tVal, true},
+	{"invoke dotV", `{{template "dotV" .U}}`, "v", tVal, true},
+	{"invoke nested int", `{{template "nested" .I}}`, "17", tVal, true},
+	{"variable declared by template", `{{template "nested" $x:=.SI}},{{index $x 1}}`, "[3 4 5],4", tVal, true},
+
+	// User-defined function: test argument evaluator.
+	{"testFunc literal", `{{oneArg "joe"}}`, "oneArg=joe", tVal, true},
+	{"testFunc .", `{{oneArg .}}`, "oneArg=joe", "joe", true},
+}
+
+// These strings are also in testdata/*.
+const multiText1 = `
+	{{define "x"}}TEXT{{end}}
+	{{define "dotV"}}{{.V}}{{end}}
+`
+
+const multiText2 = `
+	{{define "dot"}}{{.}}{{end}}
+	{{define "nested"}}{{template "dot" .}}{{end}}
+`
+
+func TestMultiExecute(t *testing.T) {
+	// Declare a couple of templates first.
+	template, err := New("root").Parse(multiText1)
+	if err != nil {
+		t.Fatalf("parse error for 1: %s", err)
+	}
+	_, err = template.Parse(multiText2)
+	if err != nil {
+		t.Fatalf("parse error for 2: %s", err)
+	}
+	testExecute(multiExecTests, template, t)
+}
+
+func TestParseFiles(t *testing.T) {
+	_, err := ParseFiles("DOES NOT EXIST")
+	if err == nil {
+		t.Error("expected error for non-existent file; got none")
+	}
+	template := New("root")
+	_, err = template.ParseFiles("testdata/file1.tmpl", "testdata/file2.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(multiExecTests, template, t)
+}
+
+func TestParseGlob(t *testing.T) {
+	_, err := ParseGlob("DOES NOT EXIST")
+	if err == nil {
+		t.Error("expected error for non-existent file; got none")
+	}
+	_, err = New("error").ParseGlob("[x")
+	if err == nil {
+		t.Error("expected error for bad pattern; got none")
+	}
+	template := New("root")
+	_, err = template.ParseGlob("testdata/file*.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(multiExecTests, template, t)
+}
+
+// In these tests, actual content (not just template definitions) comes from the parsed files.
+
+var templateFileExecTests = []execTest{
+	{"test", `{{template "tmpl1.tmpl"}}{{template "tmpl2.tmpl"}}`, "template1\n\ny\ntemplate2\n\nx\n", 0, true},
+}
+
+func TestParseFilesWithData(t *testing.T) {
+	template, err := New("root").ParseFiles("testdata/tmpl1.tmpl", "testdata/tmpl2.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(templateFileExecTests, template, t)
+}
+
+func TestParseGlobWithData(t *testing.T) {
+	template, err := New("root").ParseGlob("testdata/tmpl*.tmpl")
+	if err != nil {
+		t.Fatalf("error parsing files: %v", err)
+	}
+	testExecute(templateFileExecTests, template, t)
+}
+
+const (
+	cloneText1 = `{{define "a"}}{{template "b"}}{{template "c"}}{{end}}`
+	cloneText2 = `{{define "b"}}b{{end}}`
+	cloneText3 = `{{define "c"}}root{{end}}`
+	cloneText4 = `{{define "c"}}clone{{end}}`
+)
+
+// Issue 7032
+func TestAddParseTreeToUnparsedTemplate(t *testing.T) {
+	master := "{{define \"master\"}}{{end}}"
+	tmpl := New("master")
+	tree, err := parse.Parse("master", master, "", "", nil)
+	if err != nil {
+		t.Fatalf("unexpected parse err: %v", err)
+	}
+	masterTree := tree["master"]
+	tmpl.AddParseTree("master", masterTree) // used to panic
+}
+
+func TestRedefinition(t *testing.T) {
+	var tmpl *Template
+	var err error
+	if tmpl, err = New("tmpl1").Parse(`{{define "test"}}foo{{end}}`); err != nil {
+		t.Fatalf("parse 1: %v", err)
+	}
+	if _, err = tmpl.Parse(`{{define "test"}}bar{{end}}`); err != nil {
+		t.Fatalf("got error %v, expected nil", err)
+	}
+	if _, err = tmpl.New("tmpl2").Parse(`{{define "test"}}bar{{end}}`); err != nil {
+		t.Fatalf("got error %v, expected nil", err)
+	}
+}
+
+// Issue 10879
+func TestEmptyTemplateCloneCrash(t *testing.T) {
+	t1 := New("base")
+	t1.Clone() // used to panic
+}
+
+// Issue 10910, 10926
+func TestTemplateLookUp(t *testing.T) {
+	t.Skip("broken on html/template") // TODO
+	t1 := New("foo")
+	if t1.Lookup("foo") != nil {
+		t.Error("Lookup returned non-nil value for undefined template foo")
+	}
+	t1.New("bar")
+	if t1.Lookup("bar") != nil {
+		t.Error("Lookup returned non-nil value for undefined template bar")
+	}
+	t1.Parse(`{{define "foo"}}test{{end}}`)
+	if t1.Lookup("foo") == nil {
+		t.Error("Lookup returned nil value for defined template")
+	}
+}
+
+func TestParse(t *testing.T) {
+	// In multiple calls to Parse with the same receiver template, only one call
+	// can contain text other than space, comments, and template definitions
+	t1 := New("test")
+	if _, err := t1.Parse(`{{define "test"}}{{end}}`); err != nil {
+		t.Fatalf("parsing test: %s", err)
+	}
+	if _, err := t1.Parse(`{{define "test"}}{{/* this is a comment */}}{{end}}`); err != nil {
+		t.Fatalf("parsing test: %s", err)
+	}
+	if _, err := t1.Parse(`{{define "test"}}foo{{end}}`); err != nil {
+		t.Fatalf("parsing test: %s", err)
+	}
+}
+
+func TestEmptyTemplate(t *testing.T) {
+	cases := []struct {
+		defn []string
+		in   string
+		want string
+	}{
+		{[]string{"x", "y"}, "", "y"},
+		{[]string{""}, "once", ""},
+		{[]string{"", ""}, "twice", ""},
+		{[]string{"{{.}}", "{{.}}"}, "twice", "twice"},
+		{[]string{"{{/* a comment */}}", "{{/* a comment */}}"}, "comment", ""},
+		{[]string{"{{.}}", ""}, "twice", "twice"}, // TODO: should want "" not "twice"
+	}
+
+	for i, c := range cases {
+		root := New("root")
+
+		var (
+			m   *Template
+			err error
+		)
+		for _, d := range c.defn {
+			m, err = root.New(c.in).Parse(d)
+			if err != nil {
+				t.Fatal(err)
+			}
+		}
+		buf := &bytes.Buffer{}
+		if err := m.Execute(buf, c.in); err != nil {
+			t.Error(i, err)
+			continue
+		}
+		if buf.String() != c.want {
+			t.Errorf("expected string %q: got %q", c.want, buf.String())
+		}
+	}
+}
+
+// Issue 19249 was a regression in 1.8 caused by the handling of empty
+// templates added in that release, which got different answers depending
+// on the order templates appeared in the internal map.
+func TestIssue19294(t *testing.T) {
+	// The empty block in "xhtml" should be replaced during execution
+	// by the contents of "stylesheet", but if the internal map associating
+	// names with templates is built in the wrong order, the empty block
+	// looks non-empty and this doesn't happen.
+	var inlined = map[string]string{
+		"stylesheet": `{{define "stylesheet"}}stylesheet{{end}}`,
+		"xhtml":      `{{block "stylesheet" .}}{{end}}`,
+	}
+	all := []string{"stylesheet", "xhtml"}
+	for i := 0; i < 100; i++ {
+		res, err := New("title.xhtml").Parse(`{{template "xhtml" .}}`)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for _, name := range all {
+			_, err := res.New(name).Parse(inlined[name])
+			if err != nil {
+				t.Fatal(err)
+			}
+		}
+		var buf bytes.Buffer
+		res.Execute(&buf, 0)
+		if buf.String() != "stylesheet" {
+			t.Fatalf("iteration %d: got %q; expected %q", i, buf.String(), "stylesheet")
+		}
+	}
+}
diff --git a/src/html/template/testdata/file1.tmpl b/src/html/template/testdata/file1.tmpl
new file mode 100644
index 0000000000..febf9d9f89
--- /dev/null
+++ b/src/html/template/testdata/file1.tmpl
@@ -0,0 +1,2 @@
+{{define "x"}}TEXT{{end}}
+{{define "dotV"}}{{.V}}{{end}}
diff --git a/src/html/template/testdata/file2.tmpl b/src/html/template/testdata/file2.tmpl
new file mode 100644
index 0000000000..39bf6fb9ee
--- /dev/null
+++ b/src/html/template/testdata/file2.tmpl
@@ -0,0 +1,2 @@
+{{define "dot"}}{{.}}{{end}}
+{{define "nested"}}{{template "dot" .}}{{end}}
diff --git a/src/html/template/testdata/tmpl1.tmpl b/src/html/template/testdata/tmpl1.tmpl
new file mode 100644
index 0000000000..b72b3a340c
--- /dev/null
+++ b/src/html/template/testdata/tmpl1.tmpl
@@ -0,0 +1,3 @@
+template1
+{{define "x"}}x{{end}}
+{{template "y"}}
diff --git a/src/html/template/testdata/tmpl2.tmpl b/src/html/template/testdata/tmpl2.tmpl
new file mode 100644
index 0000000000..16beba6e7d
--- /dev/null
+++ b/src/html/template/testdata/tmpl2.tmpl
@@ -0,0 +1,3 @@
+template2
+{{define "y"}}y{{end}}
+{{template "x"}}
diff --git a/src/text/template/multi_test.go b/src/text/template/multi_test.go
index bf1f1b2701..34d2378e38 100644
--- a/src/text/template/multi_test.go
+++ b/src/text/template/multi_test.go
@@ -359,6 +359,7 @@ func TestEmptyTemplate(t *testing.T) {
 		in   string
 		want string
 	}{
+		{[]string{"x", "y"}, "", "y"},
 		{[]string{""}, "once", ""},
 		{[]string{"", ""}, "twice", ""},
 		{[]string{"{{.}}", "{{.}}"}, "twice", "twice"},