change-src-attr-prepare-a-script.html

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This test has a WPT meta file that expects 1 subtest issues.
This WPT test may be referenced by the following Test IDs:
- /html/semantics/scripting-1/the-script-element/change-src-attr-prepare-a-script.html - WPT Dashboard Interop Dashboard

<!doctype html>

<meta charset=utf-8>

<link rel=help href=https://github.com/whatwg/html/pull/10188#discussion_r1719338657>

<title>Adding/changing src attribute does "prepare the script"</title>

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

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

<body>

<script>

// The "old" HTML Standard specification text around `src` attribute mutation

// for non-parser-inserted scripts *ONLY* "prepared"/run the script iff the src

// attribute "previously had no such attribute". This changed in

// https://github.com/whatwg/html/pull/10188 to align with a majority of

// browsers. This test ensures that `src` mutations on these kinds of scripts

// *where a previous valid `src` attribute existed* do indeed "prepare" the

// script.

promise_test(async () => {

  window.didExecute = false;

  const script = document.createElement('script');

  // Invalid type, so the script won't execute upon insertion.

  script.type = 'invalid';

  script.src = 'resources/flag-setter.js';

  document.body.append(script);

  assert_false(window.didExecute);

  // Make script valid, but don't immediately execute it.

  script.type = '';

  const scriptPromise = new Promise(resolve => {

    script.onload = resolve;

});

  // Mutating the `src` attribute, which has an existing valid value, triggers

  // the "prepare a script" algorithm via the post-connection steps.

  script.src = 'resources/flag-setter.js?different';

  await scriptPromise;

  assert_true(window.didExecute);

}, "Mutating `src` attribute from an already-valid value does 'prepare' the script");

</script>

</body>