1 files changed, 89 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/semantics/scripting-1/the-script-element/microtasks/resources/checkpoint-after-error-event.js b/testing/web-platform/tests/html/semantics/scripting-1/the-script-element/microtasks/resources/checkpoint-after-error-event.js
new file mode 100644
index 0000000000..1a2b9404a7
--- /dev/null
+++ b/testing/web-platform/tests/html/semantics/scripting-1/the-script-element/microtasks/resources/checkpoint-after-error-event.js
@@ -0,0 +1,89 @@
+// The `then` handlers for `Promise.resolve()` are evaluated in the first
+// microtasks checkpoint after `Promise.resolve()`.
+
+self.setup({allow_uncaught_exception: true});
+
+// ----------------------------------------------------------------
+// Check when microtasks checkpoint is performed
+// - Around `self`'s error event fired via
+//   https://html.spec.whatwg.org/C/#report-the-error during
+//   - https://html.spec.whatwg.org/C/#run-a-classic-script or
+//   - https://html.spec.whatwg.org/C/#run-a-module-script.
+
+// The expectation is: the `then` handlers are evaluated after all error event
+// handlers are evaluated, not after each error event handler.
+
+// Just after each event handler is invoked,
+// https://webidl.spec.whatwg.org/#call-a-user-objects-operation
+// calls #clean-up-after-running-script, but this doesn't execute new
+// microtasks immediately, because:
+// - Before https://github.com/whatwg/html/pull/4352:
+//   #report-the-error is called before #clean-up-after-running-script by
+//   #run-a-classic-script/#run-a-module-script, so microtask checkpoint
+//   is not performed because JavaScript execution context stack is not empty.
+// - After https://github.com/whatwg/html/pull/4352:
+//   #report-the-error is called during #perform-a-microtask-checkpoint (because
+//   it is called on rejection of promises), so #perform-a-microtask-checkpoint
+//   is executed but early exited.
+self.log = [];
+
+self.addEventListener('error', () => {
+  log.push('handler 1');
+  Promise.resolve().then(() => log.push('handler 1 promise'));
+});
+self.addEventListener('error', () => {
+  log.push('handler 2');
+  Promise.resolve().then(() => log.push('handler 2 promise'));
+});
+
+// Microtasks should be executed before
+// #run-a-classic-script/#run-a-module-script is completed, and thus before
+// script evaluation scheduled by setTimeout().
+async_test(t => {
+  t.step_timeout(() => {
+      assert_array_equals(log, [
+          'handler 1',
+          'handler 2',
+          'handler 1 promise',
+          'handler 2 promise'
+        ]);
+      t.done();
+    },
+    0);
+}, "Promise resolved during #report-the-error");
+
+// ----------------------------------------------------------------
+// Check when microtasks checkpoint is performed
+// around event events other than the `self` error event cases above.
+// In this case, microtasks are executed just after each event handler is
+// invoked via #clean-up-after-running-script called from
+// https://webidl.spec.whatwg.org/#call-a-user-objects-operation,
+// because the event handlers are executed outside the
+// #prepare-to-run-script/#clean-up-after-running-script scopes in
+// #run-a-classic-script/#run-a-module-script.
+self.log2 = [];
+self.t2 = async_test(
+    "Promise resolved during event handlers other than error");
+
+self.addEventListener('message', () => {
+  log2.push('handler 1');
+  Promise.resolve().then(() => log2.push('handler 1 promise'));
+});
+self.addEventListener('message', () => {
+  log2.push('handler 2');
+  Promise.resolve().then(t2.step_func_done(() => {
+      log2.push('handler 2 promise');
+      assert_array_equals(log2, [
+          'handler 1',
+          'handler 1 promise',
+          'handler 2',
+          'handler 2 promise'
+        ]);
+    }));
+});
+
+// ----------------------------------------------------------------
+
+done();
+
+throw new Error('script 1');