tpl/internal: Sync go_templates

Closes #10411

tpl/internal/go_templates/texttemplate/doc.go

@@ -18,7 +18,6 @@ structure as execution proceeds.
 The input text for a template is UTF-8-encoded text in any format.
 "Actions"--data evaluations or control structures--are delimited by
 "{{" and "}}"; all text outside actions is copied to the output unchanged.
-Except for raw strings, actions may not span newlines, although comments can.
 
 Once parsed, a template may be executed safely in parallel, although if parallel
 executions share a Writer the output may be interleaved.
@@ -425,10 +424,10 @@ The syntax of such definitions is to surround each template declaration with a
 The define action names the template being created by providing a string
 constant. Here is a simple example:
 
-	`{{define "T1"}}ONE{{end}}
+	{{define "T1"}}ONE{{end}}
 	{{define "T2"}}TWO{{end}}
 	{{define "T3"}}{{template "T1"}} {{template "T2"}}{{end}}
-	{{template "T3"}}`
+	{{template "T3"}}
 
 This defines two templates, T1 and T2, and a third T3 that invokes the other two
 when it is executed. Finally it invokes T3. If executed this template will

tpl/internal/go_templates/texttemplate/exec.go

@@ -94,6 +94,12 @@ type missingValType struct{}
 
 var missingVal = reflect.ValueOf(missingValType{})
 
+var missingValReflectType = reflect.TypeOf(missingValType{})
+
+func isMissing(v reflect.Value) bool {
+	return v.IsValid() && v.Type() == missingValReflectType
+}
+
 // at marks the state to be on node n, for error reporting.
 func (s *state) at(node parse.Node) {
 	s.node = node
@@ -357,11 +363,19 @@ func (s *state) walkRange(dot reflect.Value, r *parse.RangeNode) {
 	oneIteration := func(index, elem reflect.Value) {
 		// Set top var (lexically the second if there are two) to the element.
 		if len(r.Pipe.Decl) > 0 {
-			s.setTopVar(1, elem)
+			if r.Pipe.IsAssign {
+				s.setVar(r.Pipe.Decl[0].Ident[0], elem)
+			} else {
+				s.setTopVar(1, elem)
+			}
 		}
 		// Set next var (lexically the first if there are two) to the index.
 		if len(r.Pipe.Decl) > 1 {
-			s.setTopVar(2, index)
+			if r.Pipe.IsAssign {
+				s.setVar(r.Pipe.Decl[1].Ident[0], index)
+			} else {
+				s.setTopVar(2, index)
+			}
 		}
 		defer s.pop(mark)
 		defer func() {
@@ -471,7 +485,7 @@ func (s *state) evalPipeline(dot reflect.Value, pipe *parse.PipeNode) (value ref
 }
 
 func (s *state) notAFunction(args []parse.Node, final reflect.Value) {
-	if len(args) > 1 || final != missingVal {
+	if len(args) > 1 || !isMissing(final) {
 		s.errorf("can't give argument to non-function %s", args[0])
 	}
 }
@@ -629,7 +643,7 @@ func (s *state) evalFieldOld(dot reflect.Value, fieldName string, node parse.Nod
 	if method := ptr.MethodByName(fieldName); method.IsValid() {
 		return s.evalCall(dot, method, false, node, fieldName, args, final)
 	}
-	hasArgs := len(args) > 1 || final != missingVal
+	hasArgs := len(args) > 1 || !isMissing(final)
 	// It's not a method; must be a field of a struct or an element of a map.
 	switch receiver.Kind() {
 	case reflect.Struct:
@@ -700,7 +714,7 @@ func (s *state) evalCallOld(dot, fun reflect.Value, isBuiltin bool, node parse.N
 	}
 	typ := fun.Type()
 	numIn := len(args)
-	if final != missingVal {
+	if !isMissing(final) {
 		numIn++
 	}
 	numFixed := len(args)
@@ -763,7 +777,7 @@ func (s *state) evalCallOld(dot, fun reflect.Value, isBuiltin bool, node parse.N
 		}
 	}
 	// Add final value if necessary.
-	if final != missingVal {
+	if !isMissing(final) {
 		t := typ.In(typ.NumIn() - 1)
 		if typ.IsVariadic() {
 			if numIn-1 < numFixed {

tpl/internal/go_templates/texttemplate/exec_test.go

@@ -695,6 +695,8 @@ var execTests = []execTest{
 	{"bug18a", "{{eq . '.'}}", "true", '.', true},
 	{"bug18b", "{{eq . 'e'}}", "true", 'e', true},
 	{"bug18c", "{{eq . 'P'}}", "true", 'P', true},
+
+	{"issue56490", "{{$i := 0}}{{$x := 0}}{{range $i = .AI}}{{end}}{{$i}}", "5", tVal, true},
 }
 
 func zeroArgs() string {
@@ -775,7 +777,7 @@ func mapOfThree() any {
 }
 
 func testExecute(execTests []execTest, template *Template, t *testing.T) {
-	b := new(bytes.Buffer)
+	b := new(strings.Builder)
 	funcs := FuncMap{
 		"add":         add,
 		"count":       count,
@@ -864,7 +866,7 @@ func TestDelims(t *testing.T) {
 		if err != nil {
 			t.Fatalf("delim %q text %q parse err %s", left, text, err)
 		}
-		var b = new(bytes.Buffer)
+		var b = new(strings.Builder)
 		err = tmpl.Execute(b, value)
 		if err != nil {
 			t.Fatalf("delim %q exec err %s", left, err)
@@ -1027,7 +1029,7 @@ func TestTree(t *testing.T) {
 	if err != nil {
 		t.Fatal("parse error:", err)
 	}
-	var b bytes.Buffer
+	var b strings.Builder
 	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)
@@ -1223,33 +1225,39 @@ var cmpTests = []cmpTest{
 	{"eq .NilIface .Iface1", "false", true},
 	{"eq .NilIface 0", "false", true},
 	{"eq 0 .NilIface", "false", true},
+	{"eq .Map .Map", "true", true},        // Uncomparable types but nil is OK.
+	{"eq .Map nil", "true", true},         // Uncomparable types but nil is OK.
+	{"eq nil .Map", "true", true},         // Uncomparable types but nil is OK.
+	{"eq .Map .NonNilMap", "false", true}, // Uncomparable types but nil is OK.
 	// 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.
+	{"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 .V1", "", false},              // Uncomparable types.
+	{"eq .NonNilMap .NonNilMap", "", false}, // Uncomparable types.
 }
 
 func TestComparison(t *testing.T) {
-	b := new(bytes.Buffer)
+	b := new(strings.Builder)
 	var cmpStruct = struct {
 		Uthree, Ufour    uint
 		NegOne, Three    int
 		Ptr, NilPtr      *int
+		NonNilMap        map[int]int
 		Map              map[int]int
 		V1, V2           V
 		Iface1, NilIface fmt.Stringer
 	}{
-		Uthree: 3,
-		Ufour:  4,
-		NegOne: -1,
-		Three:  3,
-		Ptr:    new(int),
-		Iface1: b,
+		Uthree:    3,
+		Ufour:     4,
+		NegOne:    -1,
+		Three:     3,
+		Ptr:       new(int),
+		NonNilMap: make(map[int]int),
+		Iface1:    b,
 	}
 	for _, test := range cmpTests {
 		text := fmt.Sprintf("{{if %s}}true{{else}}false{{end}}", test.expr)
@@ -1281,7 +1289,7 @@ func TestMissingMapKey(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	var b bytes.Buffer
+	var b strings.Builder
 	// By default, just get "<no value>"
 	err = tmpl.Execute(&b, data)
 	if err != nil {
@@ -1451,7 +1459,7 @@ func TestBlock(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	var buf bytes.Buffer
+	var buf strings.Builder
 	if err := tmpl.Execute(&buf, "hello"); err != nil {
 		t.Fatal(err)
 	}
@@ -1557,7 +1565,7 @@ func TestAddrOfIndex(t *testing.T) {
 	}
 	for _, text := range texts {
 		tmpl := Must(New("tmpl").Parse(text))
-		var buf bytes.Buffer
+		var buf strings.Builder
 		err := tmpl.Execute(&buf, reflect.ValueOf([]V{{1}}))
 		if err != nil {
 			t.Fatalf("%s: Execute: %v", text, err)
@@ -1613,7 +1621,7 @@ func TestInterfaceValues(t *testing.T) {
 
 	for _, tt := range tests {
 		tmpl := Must(New("tmpl").Parse(tt.text))
-		var buf bytes.Buffer
+		var buf strings.Builder
 		err := tmpl.Execute(&buf, map[string]any{
 			"PlusOne": func(n int) int {
 				return n + 1
@@ -1706,7 +1714,7 @@ func TestExecutePanicDuringCall(t *testing.T) {
 // Issue 31810. Check that a parenthesized first argument behaves properly.
 func TestIssue31810(t *testing.T) {
 	// A simple value with no arguments is fine.
-	var b bytes.Buffer
+	var b strings.Builder
 	const text = "{{ (.)  }}"
 	tmpl, err := New("").Parse(text)
 	if err != nil {

tpl/internal/go_templates/texttemplate/funcs.go

@@ -5,7 +5,6 @@
 package template
 
 import (
-	"bytes"
 	"errors"
 	"fmt"
 	"io"
@@ -436,14 +435,33 @@ func basicKind(v reflect.Value) (kind, error) {
 	return invalidKind, errBadComparisonType
 }
 
+// isNil returns true if v is the zero reflect.Value, or nil of its type.
+func isNil(v reflect.Value) bool {
+	if !v.IsValid() {
+		return true
+	}
+	switch v.Kind() {
+	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Pointer, reflect.Slice:
+		return v.IsNil()
+	}
+	return false
+}
+
+// canCompare reports whether v1 and v2 are both the same kind, or one is nil.
+// Called only when dealing with nillable types, or there's about to be an error.
+func canCompare(v1, v2 reflect.Value) bool {
+	k1 := v1.Kind()
+	k2 := v2.Kind()
+	if k1 == k2 {
+		return true
+	}
+	// We know the type can be compared to nil.
+	return k1 == reflect.Invalid || k2 == reflect.Invalid
+}
+
 // eq evaluates the comparison a == b || a == c || ...
 func eq(arg1 reflect.Value, arg2 ...reflect.Value) (bool, error) {
 	arg1 = indirectInterface(arg1)
-	if arg1 != zero {
-		if t1 := arg1.Type(); !t1.Comparable() {
-			return false, fmt.Errorf("uncomparable type %s: %v", t1, arg1)
-		}
-	}
 	if len(arg2) == 0 {
 		return false, errNoComparison
 	}
@@ -479,11 +497,14 @@ func eq(arg1 reflect.Value, arg2 ...reflect.Value) (bool, error) {
 			case uintKind:
 				truth = arg1.Uint() == arg.Uint()
 			default:
-				if arg == zero || arg1 == zero {
-					truth = arg1 == arg
+				if !canCompare(arg1, arg) {
+					return false, fmt.Errorf("non-comparable types %s: %v, %s: %v", arg1, arg1.Type(), arg.Type(), arg)
+				}
+				if isNil(arg1) || isNil(arg) {
+					truth = isNil(arg) == isNil(arg1)
 				} else {
-					if t2 := arg.Type(); !t2.Comparable() {
-						return false, fmt.Errorf("uncomparable type %s: %v", t2, arg)
+					if !arg.Type().Comparable() {
+						return false, fmt.Errorf("non-comparable type %s: %v", arg, arg.Type())
 					}
 					truth = arg1.Interface() == arg.Interface()
 				}
@@ -620,7 +641,7 @@ func HTMLEscapeString(s string) string {
 	if !strings.ContainsAny(s, "'\"&<>\000") {
 		return s
 	}
-	var b bytes.Buffer
+	var b strings.Builder
 	HTMLEscape(&b, []byte(s))
 	return b.String()
 }
@@ -703,7 +724,7 @@ func JSEscapeString(s string) string {
 	if strings.IndexFunc(s, jsIsSpecial) < 0 {
 		return s
 	}
-	var b bytes.Buffer
+	var b strings.Builder
 	JSEscape(&b, []byte(s))
 	return b.String()
 }
@@ -729,7 +750,9 @@ func URLQueryEscaper(args ...any) string {
 }
 
 // evalArgs formats the list of arguments into a string. It is therefore equivalent to
+//
 //	fmt.Sprint(args...)
+//
 // except that each argument is indirected (if a pointer), as required,
 // using the same rules as the default string evaluation during template
 // execution.

tpl/internal/go_templates/texttemplate/helper.go

@@ -19,6 +19,7 @@ import (
 // Must is a helper that wraps a call to a function returning (*Template, error)
 // and panics if the error is non-nil. It is intended for use in variable
 // initializations such as
+//
 //	var t = template.Must(template.New("name").Parse("text"))
 func Must(t *Template, err error) *Template {
 	if err != nil {

tpl/internal/go_templates/texttemplate/multi_test.go

@@ -10,10 +10,10 @@ package template
 // Tests for multiple-template parsing and execution.
 
 import (
-	"bytes"
 	"fmt"
 	"github.com/gohugoio/hugo/tpl/internal/go_templates/texttemplate/parse"
 	"os"
+	"strings"
 	"testing"
 )
 
@@ -245,7 +245,7 @@ func TestClone(t *testing.T) {
 		}
 	}
 	// Execute root.
-	var b bytes.Buffer
+	var b strings.Builder
 	err = root.ExecuteTemplate(&b, "a", 0)
 	if err != nil {
 		t.Fatal(err)
@@ -284,7 +284,7 @@ func TestAddParseTree(t *testing.T) {
 		t.Fatal(err)
 	}
 	// Execute.
-	var b bytes.Buffer
+	var b strings.Builder
 	err = added.ExecuteTemplate(&b, "a", 0)
 	if err != nil {
 		t.Fatal(err)
@@ -413,7 +413,7 @@ func TestEmptyTemplate(t *testing.T) {
 				t.Fatal(err)
 			}
 		}
-		buf := &bytes.Buffer{}
+		buf := &strings.Builder{}
 		if err := m.Execute(buf, c.in); err != nil {
 			t.Error(i, err)
 			continue
@@ -448,7 +448,7 @@ func TestIssue19294(t *testing.T) {
 				t.Fatal(err)
 			}
 		}
-		var buf bytes.Buffer
+		var buf strings.Builder
 		res.Execute(&buf, 0)
 		if buf.String() != "stylesheet" {
 			t.Fatalf("iteration %d: got %q; expected %q", i, buf.String(), "stylesheet")

tpl/internal/go_templates/texttemplate/option.go

@@ -30,6 +30,7 @@ type option struct {
 //
 // missingkey: Control the behavior during execution if a map is
 // indexed with a key that is not present in the map.
+//
 //	"missingkey=default" or "missingkey=invalid"
 //		The default behavior: Do nothing and continue execution.
 //		If printed, the result of the index operation is the string
@@ -38,7 +39,6 @@ type option struct {
 //		The operation returns the zero value for the map type's element.
 //	"missingkey=error"
 //		Execution stops immediately with an error.
-//
 func (t *Template) Option(opt ...string) *Template {
 	t.init()
 	for _, s := range opt {

tpl/internal/go_templates/texttemplate/parse/lex.go

@@ -111,31 +111,36 @@ type stateFn func(*lexer) stateFn
 
 // lexer holds the state of the scanner.
 type lexer struct {
-	name        string    // the name of the input; used only for error reports
-	input       string    // the string being scanned
-	leftDelim   string    // start of action
-	rightDelim  string    // end of action
-	emitComment bool      // emit itemComment tokens.
-	pos         Pos       // current position in the input
-	start       Pos       // start position of this item
-	width       Pos       // width of last rune read from input
-	items       chan item // channel of scanned items
-	parenDepth  int       // nesting depth of ( ) exprs
-	line        int       // 1+number of newlines seen
-	startLine   int       // start line of this item
-	breakOK     bool      // break keyword allowed
-	continueOK  bool      // continue keyword allowed
+	name         string // the name of the input; used only for error reports
+	input        string // the string being scanned
+	leftDelim    string // start of action marker
+	rightDelim   string // end of action marker
+	pos          Pos    // current position in the input
+	start        Pos    // start position of this item
+	atEOF        bool   // we have hit the end of input and returned eof
+	parenDepth   int    // nesting depth of ( ) exprs
+	line         int    // 1+number of newlines seen
+	startLine    int    // start line of this item
+	item         item   // item to return to parser
+	insideAction bool   // are we inside an action?
+	options      lexOptions
+}
+
+// lexOptions control behavior of the lexer. All default to false.
+type lexOptions struct {
+	emitComment bool // emit itemComment tokens.
+	breakOK     bool // break keyword allowed
+	continueOK  bool // continue keyword allowed
 }
 
 // next returns the next rune in the input.
 func (l *lexer) next() rune {
 	if int(l.pos) >= len(l.input) {
-		l.width = 0
+		l.atEOF = true
 		return eof
 	}
 	r, w := utf8.DecodeRuneInString(l.input[l.pos:])
-	l.width = Pos(w)
-	l.pos += l.width
+	l.pos += Pos(w)
 	if r == '\n' {
 		l.line++
 	}
@@ -149,23 +154,41 @@ func (l *lexer) peek() rune {
 	return r
 }
 
-// backup steps back one rune. Can only be called once per call of next.
+// backup steps back one rune.
 func (l *lexer) backup() {
-	l.pos -= l.width
-	// Correct newline count.
-	if l.width == 1 && l.input[l.pos] == '\n' {
-		l.line--
+	if !l.atEOF && l.pos > 0 {
+		r, w := utf8.DecodeLastRuneInString(l.input[:l.pos])
+		l.pos -= Pos(w)
+		// Correct newline count.
+		if r == '\n' {
+			l.line--
+		}
 	}
 }
 
-// emit passes an item back to the client.
-func (l *lexer) emit(t itemType) {
-	l.items <- item{t, l.start, l.input[l.start:l.pos], l.startLine}
+// thisItem returns the item at the current input point with the specified type
+// and advances the input.
+func (l *lexer) thisItem(t itemType) item {
+	i := item{t, l.start, l.input[l.start:l.pos], l.startLine}
 	l.start = l.pos
 	l.startLine = l.line
+	return i
+}
+
+// emit passes the trailing text as an item back to the parser.
+func (l *lexer) emit(t itemType) stateFn {
+	return l.emitItem(l.thisItem(t))
+}
+
+// emitItem passes the specified item to the parser.
+func (l *lexer) emitItem(i item) stateFn {
+	l.item = i
+	return nil
 }
 
 // ignore skips over the pending input before this point.
+// It tracks newlines in the ignored text, so use it only
+// for text that is skipped without calling l.next.
 func (l *lexer) ignore() {
 	l.line += strings.Count(l.input[l.start:l.pos], "\n")
 	l.start = l.pos
@@ -191,25 +214,31 @@ func (l *lexer) acceptRun(valid string) {
 // errorf returns an error token and terminates the scan by passing
 // back a nil pointer that will be the next state, terminating l.nextItem.
 func (l *lexer) errorf(format string, args ...any) stateFn {
-	l.items <- item{itemError, l.start, fmt.Sprintf(format, args...), l.startLine}
+	l.item = item{itemError, l.start, fmt.Sprintf(format, args...), l.startLine}
+	l.start = 0
+	l.pos = 0
+	l.input = l.input[:0]
 	return nil
 }
 
 // nextItem returns the next item from the input.
 // Called by the parser, not in the lexing goroutine.
 func (l *lexer) nextItem() item {
-	return <-l.items
-}
-
-// drain drains the output so the lexing goroutine will exit.
-// Called by the parser, not in the lexing goroutine.
-func (l *lexer) drain() {
-	for range l.items {
+	l.item = item{itemEOF, l.pos, "EOF", l.startLine}
+	state := lexText
+	if l.insideAction {
+		state = lexInsideAction
+	}
+	for {
+		state = state(l)
+		if state == nil {
+			return l.item
+		}
 	}
 }
 
 // lex creates a new scanner for the input string.
-func lex(name, input, left, right string, emitComment bool) *lexer {
+func lex(name, input, left, right string) *lexer {
 	if left == "" {
 		left = leftDelim
 	}
@@ -217,27 +246,17 @@ func lex(name, input, left, right string, emitComment bool) *lexer {
 		right = rightDelim
 	}
 	l := &lexer{
-		name:        name,
-		input:       input,
-		leftDelim:   left,
-		rightDelim:  right,
-		emitComment: emitComment,
-		items:       make(chan item),
-		line:        1,
-		startLine:   1,
+		name:         name,
+		input:        input,
+		leftDelim:    left,
+		rightDelim:   right,
+		line:         1,
+		startLine:    1,
+		insideAction: false,
 	}
-	go l.run()
 	return l
 }
 
-// run runs the state machine for the lexer.
-func (l *lexer) run() {
-	for state := lexText; state != nil; {
-		state = state(l)
-	}
-	close(l.items)
-}
-
 // state functions
 
 const (
@@ -249,31 +268,33 @@ const (
 
 // lexText scans until an opening action delimiter, "{{".
 func lexText(l *lexer) stateFn {
-	l.width = 0
 	if x := strings.Index(l.input[l.pos:], l.leftDelim); x >= 0 {
-		ldn := Pos(len(l.leftDelim))
-		l.pos += Pos(x)
-		trimLength := Pos(0)
-		if hasLeftTrimMarker(l.input[l.pos+ldn:]) {
-			trimLength = rightTrimLength(l.input[l.start:l.pos])
-		}
-		l.pos -= trimLength
-		if l.pos > l.start {
+		if x > 0 {
+			l.pos += Pos(x)
+			// Do we trim any trailing space?
+			trimLength := Pos(0)
+			delimEnd := l.pos + Pos(len(l.leftDelim))
+			if hasLeftTrimMarker(l.input[delimEnd:]) {
+				trimLength = rightTrimLength(l.input[l.start:l.pos])
+			}
+			l.pos -= trimLength
 			l.line += strings.Count(l.input[l.start:l.pos], "\n")
-			l.emit(itemText)
+			i := l.thisItem(itemText)
+			l.pos += trimLength
+			l.ignore()
+			if len(i.val) > 0 {
+				return l.emitItem(i)
+			}
 		}
-		l.pos += trimLength
-		l.ignore()
 		return lexLeftDelim
 	}
 	l.pos = Pos(len(l.input))
 	// Correctly reached EOF.
 	if l.pos > l.start {
 		l.line += strings.Count(l.input[l.start:l.pos], "\n")
-		l.emit(itemText)
+		return l.emit(itemText)
 	}
-	l.emit(itemEOF)
-	return nil
+	return l.emit(itemEOF)
 }
 
 // rightTrimLength returns the length of the spaces at the end of the string.
@@ -298,6 +319,7 @@ func leftTrimLength(s string) Pos {
 }
 
 // lexLeftDelim scans the left delimiter, which is known to be present, possibly with a trim marker.
+// (The text to be trimmed has already been emitted.)
 func lexLeftDelim(l *lexer) stateFn {
 	l.pos += Pos(len(l.leftDelim))
 	trimSpace := hasLeftTrimMarker(l.input[l.pos:])
@@ -310,28 +332,27 @@ func lexLeftDelim(l *lexer) stateFn {
 		l.ignore()
 		return lexComment
 	}
-	l.emit(itemLeftDelim)
+	i := l.thisItem(itemLeftDelim)
+	l.insideAction = true
 	l.pos += afterMarker
 	l.ignore()
 	l.parenDepth = 0
-	return lexInsideAction
+	return l.emitItem(i)
 }
 
 // lexComment scans a comment. The left comment marker is known to be present.
 func lexComment(l *lexer) stateFn {
 	l.pos += Pos(len(leftComment))
-	i := strings.Index(l.input[l.pos:], rightComment)
-	if i < 0 {
+	x := strings.Index(l.input[l.pos:], rightComment)
+	if x < 0 {
 		return l.errorf("unclosed comment")
 	}
-	l.pos += Pos(i + len(rightComment))
+	l.pos += Pos(x + len(rightComment))
 	delim, trimSpace := l.atRightDelim()
 	if !delim {
 		return l.errorf("comment ends before closing delimiter")
 	}
-	if l.emitComment {
-		l.emit(itemComment)
-	}
+	i := l.thisItem(itemComment)
 	if trimSpace {
 		l.pos += trimMarkerLen
 	}
@@ -340,23 +361,27 @@ func lexComment(l *lexer) stateFn {
 		l.pos += leftTrimLength(l.input[l.pos:])
 	}
 	l.ignore()
+	if l.options.emitComment {
+		return l.emitItem(i)
+	}
 	return lexText
 }
 
 // lexRightDelim scans the right delimiter, which is known to be present, possibly with a trim marker.
 func lexRightDelim(l *lexer) stateFn {
-	trimSpace := hasRightTrimMarker(l.input[l.pos:])
+	_, trimSpace := l.atRightDelim()
 	if trimSpace {
 		l.pos += trimMarkerLen
 		l.ignore()
 	}
 	l.pos += Pos(len(l.rightDelim))
-	l.emit(itemRightDelim)
+	i := l.thisItem(itemRightDelim)
 	if trimSpace {
 		l.pos += leftTrimLength(l.input[l.pos:])
 		l.ignore()
 	}
-	return lexText
+	l.insideAction = false
+	return l.emitItem(i)
 }
 
 // lexInsideAction scans the elements inside action delimiters.
@@ -378,14 +403,14 @@ func lexInsideAction(l *lexer) stateFn {
 		l.backup() // Put space back in case we have " -}}".
 		return lexSpace
 	case r == '=':
-		l.emit(itemAssign)
+		return l.emit(itemAssign)
 	case r == ':':
 		if l.next() != '=' {
 			return l.errorf("expected :=")
 		}
-		l.emit(itemDeclare)
+		return l.emit(itemDeclare)
 	case r == '|':
-		l.emit(itemPipe)
+		return l.emit(itemPipe)
 	case r == '"':
 		return lexQuote
 	case r == '`':
@@ -410,20 +435,19 @@ func lexInsideAction(l *lexer) stateFn {
 		l.backup()
 		return lexIdentifier
 	case r == '(':
-		l.emit(itemLeftParen)
 		l.parenDepth++
+		return l.emit(itemLeftParen)
 	case r == ')':
-		l.emit(itemRightParen)
 		l.parenDepth--
 		if l.parenDepth < 0 {
-			return l.errorf("unexpected right paren %#U", r)
+			return l.errorf("unexpected right paren")
 		}
+		return l.emit(itemRightParen)
 	case r <= unicode.MaxASCII && unicode.IsPrint(r):
-		l.emit(itemChar)
+		return l.emit(itemChar)
 	default:
 		return l.errorf("unrecognized character in action: %#U", r)
 	}
-	return lexInsideAction
 }
 
 // lexSpace scans a run of space characters.
@@ -448,13 +472,11 @@ func lexSpace(l *lexer) stateFn {
 			return lexRightDelim // On the delim, so go right to that.
 		}
 	}
-	l.emit(itemSpace)
-	return lexInsideAction
+	return l.emit(itemSpace)
 }
 
 // lexIdentifier scans an alphanumeric.
 func lexIdentifier(l *lexer) stateFn {
-Loop:
 	for {
 		switch r := l.next(); {
 		case isAlphaNumeric(r):
@@ -468,22 +490,19 @@ Loop:
 			switch {
 			case key[word] > itemKeyword:
 				item := key[word]
-				if item == itemBreak && !l.breakOK || item == itemContinue && !l.continueOK {
-					l.emit(itemIdentifier)
-				} else {
-					l.emit(item)
+				if item == itemBreak && !l.options.breakOK || item == itemContinue && !l.options.continueOK {
+					return l.emit(itemIdentifier)
 				}
+				return l.emit(item)
 			case word[0] == '.':
-				l.emit(itemField)
+				return l.emit(itemField)
 			case word == "true", word == "false":
-				l.emit(itemBool)
+				return l.emit(itemBool)
 			default:
-				l.emit(itemIdentifier)
+				return l.emit(itemIdentifier)
 			}
-			break Loop
 		}
 	}
-	return lexInsideAction
 }
 
 // lexField scans a field: .Alphanumeric.
@@ -496,8 +515,7 @@ func lexField(l *lexer) stateFn {
 // The $ has been scanned.
 func lexVariable(l *lexer) stateFn {
 	if l.atTerminator() { // Nothing interesting follows -> "$".
-		l.emit(itemVariable)
-		return lexInsideAction
+		return l.emit(itemVariable)
 	}
 	return lexFieldOrVariable(l, itemVariable)
 }
@@ -507,11 +525,9 @@ func lexVariable(l *lexer) stateFn {
 func lexFieldOrVariable(l *lexer, typ itemType) stateFn {
 	if l.atTerminator() { // Nothing interesting follows -> "." or "$".
 		if typ == itemVariable {
-			l.emit(itemVariable)
-		} else {
-			l.emit(itemDot)
+			return l.emit(itemVariable)
 		}
-		return lexInsideAction
+		return l.emit(itemDot)
 	}
 	var r rune
 	for {
@@ -524,8 +540,7 @@ func lexFieldOrVariable(l *lexer, typ itemType) stateFn {
 	if !l.atTerminator() {
 		return l.errorf("bad character %#U", r)
 	}
-	l.emit(typ)
-	return lexInsideAction
+	return l.emit(typ)
 }
 
 // atTerminator reports whether the input is at valid termination character to
@@ -541,13 +556,7 @@ func (l *lexer) atTerminator() bool {
 	case eof, '.', ',', '|', ':', ')', '(':
 		return true
 	}
-	// Does r start the delimiter? This can be ambiguous (with delim=="//", $x/2 will
-	// succeed but should fail) but only in extremely rare cases caused by willfully
-	// bad choice of delimiter.
-	if rd, _ := utf8.DecodeRuneInString(l.rightDelim); rd == r {
-		return true
-	}
-	return false
+	return strings.HasPrefix(l.input[l.pos:], l.rightDelim)
 }
 
 // lexChar scans a character constant. The initial quote is already
@@ -567,8 +576,7 @@ Loop:
 			break Loop
 		}
 	}
-	l.emit(itemCharConstant)
-	return lexInsideAction
+	return l.emit(itemCharConstant)
 }
 
 // lexNumber scans a number: decimal, octal, hex, float, or imaginary. This
@@ -584,11 +592,9 @@ func lexNumber(l *lexer) stateFn {
 		if !l.scanNumber() || l.input[l.pos-1] != 'i' {
 			return l.errorf("bad number syntax: %q", l.input[l.start:l.pos])
 		}
-		l.emit(itemComplex)
-	} else {
-		l.emit(itemNumber)
+		return l.emit(itemComplex)
 	}
-	return lexInsideAction
+	return l.emit(itemNumber)
 }
 
 func (l *lexer) scanNumber() bool {
@@ -644,8 +650,7 @@ Loop:
 			break Loop
 		}
 	}
-	l.emit(itemString)
-	return lexInsideAction
+	return l.emit(itemString)
 }
 
 // lexRawQuote scans a raw quoted string.
@@ -659,8 +664,7 @@ Loop:
 			break Loop
 		}
 	}
-	l.emit(itemRawString)
-	return lexInsideAction
+	return l.emit(itemRawString)
 }
 
 // isSpace reports whether r is a space character.

tpl/internal/go_templates/texttemplate/parse/lex_test.go

@@ -362,8 +362,7 @@ var lexTests = []lexTest{
 	{"extra right paren", "{{3)}}", []item{
 		tLeft,
 		mkItem(itemNumber, "3"),
-		tRpar,
-		mkItem(itemError, `unexpected right paren U+0029 ')'`),
+		mkItem(itemError, "unexpected right paren"),
 	}},
 
 	// Fixed bugs
@@ -397,7 +396,12 @@ var lexTests = []lexTest{
 
 // collect gathers the emitted items into a slice.
 func collect(t *lexTest, left, right string) (items []item) {
-	l := lex(t.name, t.input, left, right, true)
+	l := lex(t.name, t.input, left, right)
+	l.options = lexOptions{
+		emitComment: true,
+		breakOK:     true,
+		continueOK:  true,
+	}
 	for {
 		item := l.nextItem()
 		items = append(items, item)
@@ -434,7 +438,9 @@ func TestLex(t *testing.T) {
 		items := collect(&test, "", "")
 		if !equal(items, test.items, false) {
 			t.Errorf("%s: got\n\t%+v\nexpected\n\t%v", test.name, items, test.items)
+			return // TODO
 		}
+		t.Log(test.name, "OK")
 	}
 }
 
@@ -472,6 +478,39 @@ func TestDelims(t *testing.T) {
 	}
 }
 
+func TestDelimsAlphaNumeric(t *testing.T) {
+	test := lexTest{"right delimiter with alphanumeric start", "{{hub .host hub}}", []item{
+		mkItem(itemLeftDelim, "{{hub"),
+		mkItem(itemSpace, " "),
+		mkItem(itemField, ".host"),
+		mkItem(itemSpace, " "),
+		mkItem(itemRightDelim, "hub}}"),
+		tEOF,
+	}}
+	items := collect(&test, "{{hub", "hub}}")
+
+	if !equal(items, test.items, false) {
+		t.Errorf("%s: got\n\t%v\nexpected\n\t%v", test.name, items, test.items)
+	}
+}
+
+func TestDelimsAndMarkers(t *testing.T) {
+	test := lexTest{"delims that look like markers", "{{- .x -}} {{- - .x - -}}", []item{
+		mkItem(itemLeftDelim, "{{- "),
+		mkItem(itemField, ".x"),
+		mkItem(itemRightDelim, " -}}"),
+		mkItem(itemLeftDelim, "{{- "),
+		mkItem(itemField, ".x"),
+		mkItem(itemRightDelim, " -}}"),
+		tEOF,
+	}}
+	items := collect(&test, "{{- ", " -}}")
+
+	if !equal(items, test.items, false) {
+		t.Errorf("%s: got\n\t%v\nexpected\n\t%v", test.name, items, test.items)
+	}
+}
+
 var lexPosTests = []lexTest{
 	{"empty", "", []item{{itemEOF, 0, "", 1}}},
 	{"punctuation", "{{,@%#}}", []item{
@@ -533,22 +572,6 @@ func TestPos(t *testing.T) {
 	}
 }
 
-// Test that an error shuts down the lexing goroutine.
-func TestShutdown(t *testing.T) {
-	// We need to duplicate template.Parse here to hold on to the lexer.
-	const text = "erroneous{{define}}{{else}}1234"
-	lexer := lex("foo", text, "{{", "}}", false)
-	_, err := New("root").parseLexer(lexer)
-	if err == nil {
-		t.Fatalf("expected error")
-	}
-	// The error should have drained the input. Therefore, the lexer should be shut down.
-	token, ok := <-lexer.items
-	if ok {
-		t.Fatalf("input was not drained; got %v", token)
-	}
-}
-
 // parseLexer is a local version of parse that lets us pass in the lexer instead of building it.
 // We expect an error, so the tree set and funcs list are explicitly nil.
 func (t *Tree) parseLexer(lex *lexer) (tree *Tree, err error) {

tpl/internal/go_templates/texttemplate/parse/parse.go

@@ -210,7 +210,6 @@ func (t *Tree) recover(errp *error) {
 			panic(e)
 		}
 		if t != nil {
-			t.lex.drain()
 			t.stopParse()
 		}
 		*errp = e.(error)
@@ -224,8 +223,6 @@ func (t *Tree) startParse(funcs []map[string]any, lex *lexer, treeSet map[string
 	t.vars = []string{"$"}
 	t.funcs = funcs
 	t.treeSet = treeSet
-	lex.breakOK = !t.hasFunction("break")
-	lex.continueOK = !t.hasFunction("continue")
 }
 
 // stopParse terminates parsing.
@@ -243,8 +240,13 @@ func (t *Tree) stopParse() {
 func (t *Tree) Parse(text, leftDelim, rightDelim string, treeSet map[string]*Tree, funcs ...map[string]any) (tree *Tree, err error) {
 	defer t.recover(&err)
 	t.ParseName = t.Name
-	emitComment := t.Mode&ParseComments != 0
-	t.startParse(funcs, lex(t.Name, text, leftDelim, rightDelim, emitComment), treeSet)
+	lexer := lex(t.Name, text, leftDelim, rightDelim)
+	lexer.options = lexOptions{
+		emitComment: t.Mode&ParseComments != 0,
+		breakOK:     !t.hasFunction("break"),
+		continueOK:  !t.hasFunction("continue"),
+	}
+	t.startParse(funcs, lexer, treeSet)
 	t.text = text
 	t.parse()
 	t.add()
@@ -341,7 +343,9 @@ func (t *Tree) parseDefinition() {
 }
 
 // itemList:
+//
 //	textOrAction*
+//
 // Terminates at {{end}} or {{else}}, returned separately.
 func (t *Tree) itemList() (list *ListNode, next Node) {
 	list = t.newList(t.peekNonSpace().pos)
@@ -358,6 +362,7 @@ func (t *Tree) itemList() (list *ListNode, next Node) {
 }
 
 // textOrAction:
+//
 //	text | comment | action
 func (t *Tree) textOrAction() Node {
 	switch token := t.nextNonSpace(); token.typ {
@@ -380,8 +385,10 @@ func (t *Tree) clearActionLine() {
 }
 
 // Action:
+//
 //	control
 //	command ("|" command)*
+//
 // Left delim is past. Now get actions.
 // First word could be a keyword such as range.
 func (t *Tree) action() (n Node) {
@@ -412,7 +419,9 @@ func (t *Tree) action() (n Node) {
 }
 
 // Break:
+//
 //	{{break}}
+//
 // Break keyword is past.
 func (t *Tree) breakControl(pos Pos, line int) Node {
 	if token := t.nextNonSpace(); token.typ != itemRightDelim {
@@ -425,7 +434,9 @@ func (t *Tree) breakControl(pos Pos, line int) Node {
 }
 
 // Continue:
+//
 //	{{continue}}
+//
 // Continue keyword is past.
 func (t *Tree) continueControl(pos Pos, line int) Node {
 	if token := t.nextNonSpace(); token.typ != itemRightDelim {
@@ -438,6 +449,7 @@ func (t *Tree) continueControl(pos Pos, line int) Node {
 }
 
 // Pipeline:
+//
 //	declarations? command ('|' command)*
 func (t *Tree) pipeline(context string, end itemType) (pipe *PipeNode) {
 	token := t.peekNonSpace()
@@ -549,16 +561,20 @@ func (t *Tree) parseControl(allowElseIf bool, context string) (pos Pos, line int
 }
 
 // If:
+//
 //	{{if pipeline}} itemList {{end}}
 //	{{if pipeline}} itemList {{else}} itemList {{end}}
+//
 // If keyword is past.
 func (t *Tree) ifControl() Node {
 	return t.newIf(t.parseControl(true, "if"))
 }
 
 // Range:
+//
 //	{{range pipeline}} itemList {{end}}
 //	{{range pipeline}} itemList {{else}} itemList {{end}}
+//
 // Range keyword is past.
 func (t *Tree) rangeControl() Node {
 	r := t.newRange(t.parseControl(false, "range"))
@@ -566,22 +582,28 @@ func (t *Tree) rangeControl() Node {
 }
 
 // With:
+//
 //	{{with pipeline}} itemList {{end}}
 //	{{with pipeline}} itemList {{else}} itemList {{end}}
+//
 // If keyword is past.
 func (t *Tree) withControl() Node {
 	return t.newWith(t.parseControl(false, "with"))
 }
 
 // End:
+//
 //	{{end}}
+//
 // End keyword is past.
 func (t *Tree) endControl() Node {
 	return t.newEnd(t.expect(itemRightDelim, "end").pos)
 }
 
 // Else:
+//
 //	{{else}}
+//
 // Else keyword is past.
 func (t *Tree) elseControl() Node {
 	// Special case for "else if".
@@ -595,7 +617,9 @@ func (t *Tree) elseControl() Node {
 }
 
 // Block:
+//
 //	{{block stringValue pipeline}}
+//
 // Block keyword is past.
 // The name must be something that can evaluate to a string.
 // The pipeline is mandatory.
@@ -623,7 +647,9 @@ func (t *Tree) blockControl() Node {
 }
 
 // Template:
+//
 //	{{template stringValue pipeline}}
+//
 // Template keyword is past. The name must be something that can evaluate
 // to a string.
 func (t *Tree) templateControl() Node {
@@ -654,7 +680,9 @@ func (t *Tree) parseTemplateName(token item, context string) (name string) {
 }
 
 // command:
+//
 //	operand (space operand)*
+//
 // space-separated arguments up to a pipeline character or right delimiter.
 // we consume the pipe character but leave the right delim to terminate the action.
 func (t *Tree) command() *CommandNode {
@@ -684,7 +712,9 @@ func (t *Tree) command() *CommandNode {
 }
 
 // operand:
+//
 //	term .Field*
+//
 // An operand is a space-separated component of a command,
 // a term possibly followed by field accesses.
 // A nil return means the next item is not an operand.
@@ -718,12 +748,14 @@ func (t *Tree) operand() Node {
 }
 
 // term:
+//
 //	literal (number, string, nil, boolean)
 //	function (identifier)
 //	.
 //	.Field
 //	$
 //	'(' pipeline ')'
+//
 // A term is a simple "expression".
 // A nil return means the next item is not a term.
 func (t *Tree) term() Node {

tpl/internal/go_templates/texttemplate/parse/parse_test.go

@@ -492,7 +492,7 @@ var errorTests = []parseTest{
 		hasError, `unclosed left paren`},
 	{"rparen",
 		"{{.X 1 2 3 ) }}",
-		hasError, `unexpected ")" in command`},
+		hasError, "unexpected right paren"},
 	{"rparen2",
 		"{{(.X 1 2 3",
 		hasError, `unclosed action`},
@@ -600,7 +600,8 @@ func TestBlock(t *testing.T) {
 }
 
 func TestLineNum(t *testing.T) {
-	const count = 100
+	// const count = 100
+	const count = 3
 	text := strings.Repeat("{{printf 1234}}\n", count)
 	tree, err := New("bench").Parse(text, "", "", make(map[string]*Tree), builtins)
 	if err != nil {
@@ -614,11 +615,11 @@ func TestLineNum(t *testing.T) {
 		// Action first.
 		action := nodes[i].(*ActionNode)
 		if action.Line != line {
-			t.Fatalf("line %d: action is line %d", line, action.Line)
+			t.Errorf("line %d: action is line %d", line, action.Line)
 		}
 		pipe := action.Pipe
 		if pipe.Line != line {
-			t.Fatalf("line %d: pipe is line %d", line, pipe.Line)
+			t.Errorf("line %d: pipe is line %d", line, pipe.Line)
 		}
 	}
 }