1 files changed, 76 insertions, 0 deletions
diff --git a/testing/web-platform/tests/html/webappapis/scripting/events/eventhandler-cancellation.html b/testing/web-platform/tests/html/webappapis/scripting/events/eventhandler-cancellation.html
new file mode 100644
index 0000000000..6be581fa24
--- /dev/null
+++ b/testing/web-platform/tests/html/webappapis/scripting/events/eventhandler-cancellation.html
@@ -0,0 +1,76 @@
+<!doctype html>
+<meta charset=utf-8>
+<title></title>
+<script src=/resources/testharness.js></script>
+<script src=/resources/testharnessreport.js></script>
+<!-- A window to work with that won't trigger the harness exception detection
+     when we fire "error" events at it -->
+<iframe style="display: none"></iframe>
+<script>
+  test(function() {
+    var blob = new Blob([""]);
+    // Most targets disabled for now until
+    // https://github.com/whatwg/html/issues/2296 is sorted out.
+    var targets = [ frames[0] /*, document, document.documentElement,
+                    new Worker(URL.createObjectURL(blob) */ ];
+    // Event constructors also mostly disabled until
+    // https://github.com/whatwg/html/issues/2296 is sorted out.
+    var eventCtors = [ /* Event, */ ErrorEvent /*, MouseEvent */ ];
+    var values = [true, false, "", "abc", {}, 0, 1, -1, null, undefined,
+                  2.5, NaN, Infinity, Symbol.toStringTag ];
+    // Event types also mostly disabled pending
+    // https://github.com/whatwg/html/issues/2296
+    var eventTypes = [ "error"/*, "click", "load"*/ ];
+
+    // Variables that keep track of which subtest we're running.
+    var curTarget;
+    var curValue;
+    var curCtor;
+    var curType;
+
+    function defaultPreventedTester(event) {
+      var expectedValue;
+      if (curTarget === frames[0] &&
+          curCtor === ErrorEvent &&
+          curValue === true &&
+          curType == "error") {
+        expectedValue = true;
+      } else {
+        // This will need adjusting once we allow more targets and event
+        // constructors above!
+        expectedValue = false;
+      }
+      var valueRepr;
+      if (typeof curValue == "string") {
+        valueRepr = '"' + curValue + '"';
+      } else {
+        valueRepr = String(curValue);
+      }
+      test(function() {
+        assert_equals(event.defaultPrevented, expectedValue);
+      }, "Returning " + valueRepr +
+         " from " + String(curTarget) + "'s on" + curType +
+         " event handler while " + curCtor.name +
+         " is firing should" +
+         (expectedValue ? "" : " not") +
+         " cancel the event");
+    }
+
+    for (curCtor of eventCtors) {
+      for (curTarget of targets) {
+        for (curType of eventTypes) {
+          for (curValue of values) {
+            // We have to make sure that defaultPreventedTester is added after
+            // our event handler.
+            curTarget["on" + curType] = function() { return curValue; }
+            curTarget.addEventListener(curType, defaultPreventedTester);
+            var e = new curCtor(curType, { cancelable: true });
+            curTarget.dispatchEvent(e);
+            curTarget["on" + curType] = null;
+            curTarget.removeEventListener(curType, defaultPreventedTester);
+          }
+        }
+      }
+    }
+  }, "event handler cancellation behavior");
+</script>