tpl/internal: Sync Go template src to Go 1.20

Updates #10691

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

@@ -520,7 +520,7 @@ func lexVariable(l *lexer) stateFn {
 	return lexFieldOrVariable(l, itemVariable)
 }
 
-// lexVariable scans a field or variable: [.$]Alphanumeric.
+// lexFieldOrVariable scans a field or variable: [.$]Alphanumeric.
 // The . or $ has been scanned.
 func lexFieldOrVariable(l *lexer, typ itemType) stateFn {
 	if l.atTerminator() { // Nothing interesting follows -> "." or "$".

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

@@ -223,6 +223,11 @@ func (t *Tree) startParse(funcs []map[string]any, lex *lexer, treeSet map[string
 	t.vars = []string{"$"}
 	t.funcs = funcs
 	t.treeSet = treeSet
+	lex.options = lexOptions{
+		emitComment: t.Mode&ParseComments != 0,
+		breakOK:     !t.hasFunction("break"),
+		continueOK:  !t.hasFunction("continue"),
+	}
 }
 
 // stopParse terminates parsing.
@@ -241,11 +246,6 @@ func (t *Tree) Parse(text, leftDelim, rightDelim string, treeSet map[string]*Tre
 	defer t.recover(&err)
 	t.ParseName = t.Name
 	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()

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

@@ -394,6 +394,36 @@ func TestParseWithComments(t *testing.T) {
 	}
 }
 
+func TestKeywordsAndFuncs(t *testing.T) {
+	// Check collisions between functions and new keywords like 'break'. When a
+	// break function is provided, the parser should treat 'break' as a function,
+	// not a keyword.
+	textFormat = "%q"
+	defer func() { textFormat = "%s" }()
+
+	inp := `{{range .X}}{{break 20}}{{end}}`
+	{
+		// 'break' is a defined function, don't treat it as a keyword: it should
+		// accept an argument successfully.
+		var funcsWithKeywordFunc = map[string]any{
+			"break": func(in any) any { return in },
+		}
+		tmpl, err := New("").Parse(inp, "", "", make(map[string]*Tree), funcsWithKeywordFunc)
+		if err != nil || tmpl == nil {
+			t.Errorf("with break func: unexpected error: %v", err)
+		}
+	}
+
+	{
+		// No function called 'break'; treat it as a keyword. Results in a parse
+		// error.
+		tmpl, err := New("").Parse(inp, "", "", make(map[string]*Tree), make(map[string]any))
+		if err == nil || tmpl != nil {
+			t.Errorf("without break func: expected error; got none")
+		}
+	}
+}
+
 func TestSkipFuncCheck(t *testing.T) {
 	oldTextFormat := textFormat
 	textFormat = "%q"