link-load-event-alt-002.html

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This WPT test may be referenced by the following Test IDs:
- /html/semantics/document-metadata/the-link-element/link-load-event-alt-002.html - WPT Dashboard Interop Dashboard

<!doctype html>

<link rel="help" href="https://html.spec.whatwg.org/multipage/#the-link-element">

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

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

<body>

<script>

  async_test(function (t) {

    let reached_end = false;

    const BAD = "file:///nope-link-load-event-alt-002.css";

    const BAD_CHILD = "file:///nope-link-load-event-alt-002-child.css";

    let pendingErrors = 2;

    function addLink(doc, rel, href, title) {

      const l = doc.createElement("link");

      l.rel = rel;

      l.href = href;

      if (title) l.title = title;

      doc.head.appendChild(l);

      return l;

    function onAltError(t) {

      assert_true(reached_end, "Shouldn't fire error event synchronously");

      if (--pendingErrors == 0) {

        t.done();

    const f2 = document.createElement("iframe");

    document.body.appendChild(f2);

    const d2 = f2.contentDocument;

    const f1 = document.createElement("iframe");

    document.body.appendChild(f1);

    const d1 = f1.contentDocument;

    // Two ongoing loads on d2 are needed to trigger the deferral codepath for

    // the alternate stylesheet below.

    addLink(d2, "stylesheet", "style.css?link-load-event-alt-002-1").onerror =

      t.unreached_func("Shouldn't error");

    addLink(d2, "stylesheet", "style.css?link-load-event-alt-002-2").onerror =

      t.unreached_func("Shouldn't error");

    // This gets deferred, since there are two other loads ongoing in d2.

    const alt2 = addLink(d2, "alternate stylesheet", BAD, "aaa");

    alt2.onload = t.unreached_func("Should not load");

    alt2.onerror = t.step_func(() => onAltError(t));

    // A load for the same URL from a different document coalesces onto d2's

    // pending entry.

    const alt1 = addLink(d1, "alternate stylesheet", BAD, "bbb");

    alt1.onload = t.unreached_func("Should not load");

    alt1.onerror = t.step_func(() => onAltError(t));

    // An inline stylesheet whose @import fails to open a channel

    // synchronously. This reentrantly completes the coalesced load above

    // while d1's loader is still in the middle of parsing this very sheet.

    const s = d1.createElement("style");

    s.textContent = '@import url("' + BAD_CHILD + '");';

    d1.head.appendChild(s);

    reached_end = true;

});

</script>