template: fix deadlock.

No need for lexInsideAction to loop.
Fixes #2217.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/4963054

src/pkg/template/parse/lex.go

@@ -278,7 +278,6 @@ func lexInsideAction(l *lexer) stateFn {
 	// Either number, quoted string, or identifier.
 	// Spaces separate and are ignored.
 	// Pipe symbols separate and are emitted.
-	for {
 	if strings.HasPrefix(l.input[l.pos:], rightDelim) {
 		return lexRightDelim
 	}
@@ -323,8 +322,7 @@ func lexInsideAction(l *lexer) stateFn {
 	default:
 		return l.errorf("unrecognized character in action: %#U", r)
 	}
-	}
+	return lexInsideAction
-	return nil
 }
 
 // lexIdentifier scans an alphanumeric or field.

src/pkg/template/parse/lex_test.go

@@ -184,6 +184,20 @@ var lexTests = []lexTest{
 		tLeft,
 		{itemError, `bad number syntax: "3k"`},
 	}},
+
+	// Fixed bugs
+	// Many elements in an action blew the lookahead until
+	// we made lexInsideAction not loop.
+	{"long pipeline deadlock", "{{|||||}}", []item{
+		tLeft,
+		tPipe,
+		tPipe,
+		tPipe,
+		tPipe,
+		tPipe,
+		tRight,
+		tEOF,
+	}},
 }
 
 // collect gathers the emitted items into a slice.