Blitz - WPT: layer-import-parsing.html

wpt / css / css-cascade / parsing / layer-import-parsing.html

Data from commit:
a50cb89 wpt: run reference-named files which are themselves tests (#836) (2026-09-03)

Subtest	Status	Message
@import url("nonexist.css") layer; should be a valid layered import rule	FAIL	Cannot destructure 'undefined' value
@import url("nonexist.css") layer(A); should be a valid layered import rule	FAIL	Cannot destructure 'undefined' value
@import url("nonexist.css") layer(A.B); should be a valid layered import rule	FAIL	Cannot destructure 'undefined' value
@import url(nonexist.css) layer; should be a valid layered import rule	FAIL	Cannot destructure 'undefined' value
@import url(nonexist.css) layer(A); should be a valid layered import rule	FAIL	Cannot destructure 'undefined' value
@import url(nonexist.css) layer(A.B); should be a valid layered import rule	FAIL	Cannot destructure 'undefined' value
@import "nonexist.css" layer; should be a valid layered import rule	FAIL	Cannot destructure 'undefined' value
@import "nonexist.css" layer(A); should be a valid layered import rule	FAIL	Cannot destructure 'undefined' value
@import "nonexist.css" layer(A.B); should be a valid layered import rule	FAIL	Cannot destructure 'undefined' value
@import url("nonexist.css") layer(); should still be a valid import rule with an invalid layer declaration	FAIL	Cannot destructure 'undefined' value
@import url("nonexist.css") layer(A B); should still be a valid import rule with an invalid layer declaration	FAIL	Cannot destructure 'undefined' value
@import url("nonexist.css") layer(A . B); should still be a valid import rule with an invalid layer declaration	FAIL	Cannot destructure 'undefined' value
@import url("nonexist.css") layer(A, B, C); should still be a valid import rule with an invalid layer declaration	FAIL	Cannot destructure 'undefined' value

Enable JavaScript in test iframe

/css/css-cascade/parsing/layer-import-parsing.html

<!doctype html>
<meta charset="utf-8">
<title>@import rule with layer parsing / serialization</title>
<link rel="author" href="mailto:xiaochengh@chromium.org">
<link rel="help" href="https://drafts.csswg.org/css-cascade-5/#at-import">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script>
  function setupSheet(rule) {
    const style = document.createElement("style");
    document.head.append(style);
    const {sheet} = style;
    const {cssRules} = sheet;

    assert_equals(cssRules.length, 0, "Sheet should have no rules");
    sheet.insertRule(rule);
    assert_equals(cssRules.length, 1, "Sheet should have 1 rule");

    return {sheet, cssRules};
  }

  function test_valid_layer_import(rule, serialized) {
    if (serialized === undefined)
        serialized = rule;

    test(function() {
      const {sheet, cssRules} = setupSheet(rule);

      const serialization = cssRules[0].cssText;
      assert_equals(serialization, serialized, 'serialization should be canonical');

      const media = cssRules[0].media;
      assert_equals(media.length, 0, 'layer() should be valid');

      sheet.deleteRule(0);
      assert_equals(cssRules.length, 0, 'Sheet should have no rule');
      sheet.insertRule(serialization);
      assert_equals(cssRules.length, 1, 'Sheet should have 1 rule');

      assert_equals(cssRules[0].cssText, serialization, 'serialization should round-trip');
    }, rule + ' should be a valid layered import rule');
  }

  function test_invalid_layer_import(rule) {
    test(function() {
      const {sheet, cssRules} = setupSheet(rule);

      const media = cssRules[0].media;
      assert_not_equals(media.length, 0,
                        'invalid layer declaration should be parsed as <general-enclosed> media query');

      sheet.deleteRule(0);
      assert_equals(cssRules.length, 0, 'Sheet should have no rule');
    }, rule + ' should still be a valid import rule with an invalid layer declaration');
  }

  test_valid_layer_import('@import url("nonexist.css") layer;');
  test_valid_layer_import('@import url("nonexist.css") layer(A);');
  test_valid_layer_import('@import url("nonexist.css") layer(A.B);');

  test_valid_layer_import('@import url(nonexist.css) layer;',
                          '@import url("nonexist.css") layer;');
  test_valid_layer_import('@import url(nonexist.css) layer(A);',
                          '@import url("nonexist.css") layer(A);');
  test_valid_layer_import('@import url(nonexist.css) layer(A.B);',
                          '@import url("nonexist.css") layer(A.B);');

  test_valid_layer_import('@import "nonexist.css" layer;',
                          '@import url("nonexist.css") layer;');
  test_valid_layer_import('@import "nonexist.css" layer(A);',
                          '@import url("nonexist.css") layer(A);');
  test_valid_layer_import('@import "nonexist.css" layer(A.B);',
                          '@import url("nonexist.css") layer(A.B);');

  test_invalid_layer_import('@import url("nonexist.css") layer();');
  test_invalid_layer_import('@import url("nonexist.css") layer(A B);');
  test_invalid_layer_import('@import url("nonexist.css") layer(A . B);');
  test_invalid_layer_import('@import url("nonexist.css") layer(A, B, C);');
</script>