fix #3265: allow whitespace inside of :is()

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## Unreleased
+
+* Fix a regression with whitespace inside `:is()` ([#3265](https://github.com/evanw/esbuild/issues/3265))
+
+    The change to parse the contents of `:is()` in version 0.18.14 introduced a regression that incorrectly flagged the contents as a syntax error if the contents started with a whitespace token (for example `div:is( .foo ) {}`). This regression has been fixed.
+
 ## 0.18.15
 
 * Add the `--serve-fallback=` option ([#2904](https://github.com/evanw/esbuild/issues/2904))

internal/css_parser/css_parser_selector.go

@@ -625,6 +625,7 @@ func (p *parser) parsePseudoClassSelector(isElement bool) css_ast.SS {
 			}
 			if ok {
 				old := p.index
+				p.eat(css_lexer.TWhitespace)
 
 				// ":local" forces local names and ":global" forces global names
 				oldLocal := p.makeLocalSymbols

internal/css_parser/css_parser_test.go

@@ -699,6 +699,10 @@ func TestSelector(t *testing.T) {
 	expectPrinted(t, "a:b(:c) {}", "a:b(:c) {\n}\n", "")
 	expectPrinted(t, "a: b {}", "a: b {\n}\n", "<stdin>: WARNING: Expected identifier but found whitespace\n")
 	expectPrinted(t, ":is(a)b {}", ":is(a)b {\n}\n", "<stdin>: WARNING: Unexpected \"b\"\n")
+	expectPrinted(t, "a:b( c ) {}", "a:b(c) {\n}\n", "")
+	expectPrinted(t, "a:b( c , d ) {}", "a:b(c, d) {\n}\n", "")
+	expectPrinted(t, "a:is( c ) {}", "a:is(c) {\n}\n", "")
+	expectPrinted(t, "a:is( c , d ) {}", "a:is(c, d) {\n}\n", "")
 
 	// These test cases previously caused a hang (see https://github.com/evanw/esbuild/issues/2276)
 	expectPrinted(t, ":x(", ":x() {\n}\n", "<stdin>: WARNING: Unexpected end of file\n")