Add optional test for cloning of error stacks

Supplements web-platform-tests#17095.
Follows whatwg/html#4665 and whatwg/webidl#732.

html/infrastructure/safe-passing-of-structured-data/shared-array-buffers/identity-not-preserved.html

@@ -5,6 +5,7 @@
 <link rel="author" title="Domenic Denicola" href="mailto:d@domenic.me">
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
+<script src="/common/utils.js"></script>
 <script src="resources/test-sab.js"></script>
 
 <div id="log"></div>
@@ -13,9 +14,10 @@
 "use strict";
 
 async_test(t => {
+  const testId = token();
   const sab = new SharedArrayBuffer(1);
   window.addEventListener("message", t.step_func(({ data }) => {
-    if (data.testId !== 1) {
+    if (data.testId !== testId) {
       return;
     }
 
@@ -24,29 +26,31 @@
     t.done();
   }));
 
-  window.postMessage({ sab, testId: 1 }, "*");
+  window.postMessage({ testId, sab }, "*");
 }, "postMessaging to this window does not give back the same SharedArrayBuffer (but does use the same backing block)");
 
 async_test(t => {
+  const testId = token();
   const sab = new SharedArrayBuffer();
-  const worker = new Worker("resources/echo-worker.js");
+  const worker = new Worker("../resources/echo-worker.js");
 
   worker.addEventListener("message", t.step_func(({ data }) => {
-    if (data.testId !== 2) {
+    if (data.testId !== testId) {
       return;
     }
 
     assert_not_equals(data.sab, sab);
     t.done();
   }));
 
-  worker.postMessage({ testId: 2, sab });
+  worker.postMessage({ testId, sab });
 }, "postMessaging to a worker and back does not give back the same SharedArrayBuffer");
 
 async_test(t => {
+  const testId = token();
   const sab = new SharedArrayBuffer();
   window.addEventListener("message", t.step_func(({ data }) => {
-    if (data.testId !== 3) {
+    if (data.testId !== testId) {
       return;
     }
 
@@ -56,9 +60,9 @@
 
   const iframe = document.createElement("iframe");
   iframe.onload = t.step_func(() => {
-    iframe.contentWindow.postMessage({ testId: 3, sab }, "*");
+    iframe.contentWindow.postMessage({ testId, sab }, "*");
   });
-  iframe.src = "resources/echo-iframe.html";
+  iframe.src = "../resources/echo-iframe.html";
   document.body.appendChild(iframe);
 }, "postMessaging to an iframe and back does not give back the same SharedArrayBuffer");
 </script>

html/infrastructure/safe-passing-of-structured-data/shared-array-buffers/no-transferring.html

@@ -17,7 +17,7 @@
 
 test(() => {
   const sab = new SharedArrayBuffer();
-  const worker = new Worker("resources/echo-worker.js");
+  const worker = new Worker("../resources/echo-worker.js");
   assert_throws("DataCloneError", () => worker.postMessage(sab, [sab]));
   assert_throws("DataCloneError", () => worker.postMessage("test", [sab]));
 }, "Trying to transfer a SharedArrayBuffer to a worker throws");

html/infrastructure/safe-passing-of-structured-data/structured-cloning-error-stack-optional.sub.window.js

@@ -0,0 +1,85 @@
+// META: script=/common/utils.js
+
+// .stack properties on errors are unspecified, but are present in most
+// browsers, most of the time. https://github.com/tc39/proposal-error-stacks/ tracks standardizing them.
+// Tests will pass automatically if the .stack property isn't present.
+
+stackTests(() => {
+  return new Error('some message');
+}, 'page-created Error');
+
+stackTests(() => {
+  return new DOMException('InvalidStateError', 'some message');
+}, 'page-created DOMException');
+
+stackTests(() => {
+  try {
+    Object.defineProperty();
+  } catch (e) {
+    return e;
+  }
+}, 'JS-engine-created TypeError');
+
+stackTests(() => {
+  try {
+    HTMLParagraphElement.prototype.align;
+  } catch (e) {
+    return e;
+  }
+}, 'web API-created TypeError');
+
+stackTests(() => {
+  try {
+    document.createElement('');
+  } catch (e) {
+    return e;
+  }
+}, 'web API-created DOMException');
+
+function stackTests(errorFactory, description) {
+  async_test(t => {
+    const error = errorFactory();
+    const originalStack = error.stack;
+
+    if (!originalStack) {
+      t.done();
+      return;
+    }
+
+    const worker = new Worker('resources/echo-worker.js');
+    worker.onmessage = t.step_func_done(e => {
+      assert_equals(e.data.stack, originalStack);
+    });
+
+    worker.postMessage(error);
+  }, description + ' (worker)');
+
+  async_test(t => {
+    const thisTestId = token();
+
+    const error = errorFactory();
+    const originalStack = error.stack;
+
+    if (!originalStack) {
+      t.done();
+      return;
+    }
+
+    const iframe = document.createElement('iframe');
+    window.addEventListener('message', t.step_func(e => {
+      if (e.data.testId === thisTestId) {
+        assert_equals(e.data.error.stack, originalStack);
+        t.done();
+      }
+    }));
+
+    iframe.onload = t.step_func(() => {
+      iframe.contentWindow.postMessage({ error, testId: thisTestId }, "*");
+    });
+
+    const crossSiteEchoIFrame = new URL('resources/echo-iframe.html', location.href);
+    crossSiteEchoIFrame.hostname = '{{hosts[alt][www1]}}';
+    iframe.src = crossSiteEchoIFrame;
+    document.body.append(iframe);
+  }, description + ' (cross-site iframe)');
+}

html/infrastructure/safe-passing-of-structured-data/structured_clone_bigint.html

@@ -23,7 +23,7 @@
         //the worker is used for each test in sequence
         //worker's callback will be set for each test
         //worker's internal onmessage echoes the data back to this thread through postMessage
-        worker = new Worker("./echo.js");
+        worker = new Worker("./resources/echo-worker.js");
         testCollection = [
             function() {
                 var t = async_test("Primitive BigInt is cloned");

html/infrastructure/safe-passing-of-structured-data/structuredclone_0.html

@@ -18,7 +18,7 @@
         //the worker is used for each test in sequence
         //worker's callback will be set for each test
         //worker's internal onmessage echoes the data back to this thread through postMessage
-        worker = new Worker("./echo.js");
+        worker = new Worker("./resources/echo-worker.js");
         testCollection = [
             function() {
                 var t = async_test("Primitive string is cloned");