shadowrootadoptedstylesheets-async-fetch-mutation-remove-middle.html

Enable keyboard shortcuts

This test has a WPT meta file that expects 1 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /shadow-dom/declarative/tentative/shadowrootadoptedstylesheets/shadowrootadoptedstylesheets-async-fetch-mutation-remove-middle.html - WPT Dashboard Interop Dashboard

<!DOCTYPE html>

<title>shadowrootadoptedstylesheets mutation: remove middle placeholder before fetch</title>

<meta name="author" title="Kurt Catti-Schmidt" href="mailto:kschmi@microsoft.com" />

<link rel='help' href='https://github.com/whatwg/html/pull/11687'>

<script src='/resources/testharness.js'></script>

<script src='/resources/testharnessreport.js'></script>

<script src='./support/helpers.js'></script>

<body>

<script type="module">

  promise_test(async (t) => {

    // Remove the middle placeholder before fetch completes.

    const redUrl = "./support/styles-red.css";

    const blueUrl = "./support/styles.css";

    const greenUrl = "./support/styles-green.css";

    const { shadowRoot, testElement } = createStylesheetHost(

      [redUrl, blueUrl, greenUrl]);

    assert_equals(shadowRoot.adoptedStyleSheets.length, 3,

      "Before mutation: expected 3 placeholder(s).");

    assert_equals(shadowRoot.adoptedStyleSheets[0].cssRules.length, 0,

      "Before mutation: placeholder at index 0 should be empty.");

    assert_equals(shadowRoot.adoptedStyleSheets[1].cssRules.length, 0,

      "Before mutation: placeholder at index 1 should be empty.");

    assert_equals(shadowRoot.adoptedStyleSheets[2].cssRules.length, 0,

      "Before mutation: placeholder at index 2 should be empty.");

    const originalPlaceholders = [...shadowRoot.adoptedStyleSheets];

    shadowRoot.adoptedStyleSheets = [originalPlaceholders[0], originalPlaceholders[2]];

    assert_equals(shadowRoot.adoptedStyleSheets.length, 2,

      "adoptedStyleSheets should have two entries after removing the middle placeholder.");

    await fetchAndWait(redUrl, blueUrl, greenUrl);

    assert_equals(shadowRoot.adoptedStyleSheets.length, 2,

      "Removed placeholder's fetch should not re-insert the sheet.");

    assertSheetRule(shadowRoot, 0, "span { color: red; }", "Index 0");

    assertSheetRule(shadowRoot, 1, "span { color: green; }", "Index 1");

    assert_equals(getComputedStyle(testElement).color, "rgb(0, 128, 0)",

      "Green should win the cascade as the last remaining sheet.");

  }, "Removing middle placeholder before fetch excludes it from final adoptedStyleSheets.");

</script>

</body>