LibWeb: Make factory methods of DOM::Event fallible

Because of interdependencies between DOM::Event and UIEvents::MouseEvent
to template function fire_an_event() in WebDriverConnection.cpp, the
commit: 'LibWeb: Make factory methods of UIEvents::MouseEvent fallible'
have been squashed into this commit.

Userland/Libraries/LibWeb/DOM/AbortSignal.cpp

@@ -62,7 +62,7 @@ void AbortSignal::signal_abort(JS::Value reason)
     m_abort_algorithms.clear();
 
     // 5. Fire an event named abort at signal.
-    dispatch_event(*Event::create(realm(), HTML::EventNames::abort));
+    dispatch_event(Event::create(realm(), HTML::EventNames::abort).release_value_but_fixme_should_propagate_errors());
 }
 
 void AbortSignal::set_onabort(WebIDL::CallbackType* event_handler)

Userland/Libraries/LibWeb/DOM/Document.cpp

@@ -1006,7 +1006,7 @@ void Document::set_hovered_node(Node* node)
         // FIXME: Check if we need to dispatch these events in a specific order.
         for (auto target = old_hovered_node; target && target.ptr() != common_ancestor; target = target->parent()) {
             // FIXME: Populate the event with mouse coordinates, etc.
-            target->dispatch_event(*UIEvents::MouseEvent::create(realm(), UIEvents::EventNames::mouseleave));
+            target->dispatch_event(UIEvents::MouseEvent::create(realm(), UIEvents::EventNames::mouseleave).release_value_but_fixme_should_propagate_errors());
         }
     }
 
@@ -1015,7 +1015,7 @@ void Document::set_hovered_node(Node* node)
         // FIXME: Check if we need to dispatch these events in a specific order.
         for (auto target = m_hovered_node; target && target.ptr() != common_ancestor; target = target->parent()) {
             // FIXME: Populate the event with mouse coordinates, etc.
-            target->dispatch_event(*UIEvents::MouseEvent::create(realm(), UIEvents::EventNames::mouseenter));
+            target->dispatch_event(UIEvents::MouseEvent::create(realm(), UIEvents::EventNames::mouseenter).release_value_but_fixme_should_propagate_errors());
         }
     }
 }
@@ -1272,39 +1272,39 @@ WebIDL::ExceptionOr<JS::NonnullGCPtr<Event>> Document::create_event(DeprecatedSt
     //      then set constructor to the interface in the second column on the same row as the matching string:
     auto interface_lowercase = interface.to_lowercase();
     if (interface_lowercase == "beforeunloadevent") {
-        event = Event::create(realm, ""); // FIXME: Create BeforeUnloadEvent
+        event = TRY(Event::create(realm, "")); // FIXME: Create BeforeUnloadEvent
     } else if (interface_lowercase == "compositionevent") {
-        event = Event::create(realm, ""); // FIXME: Create CompositionEvent
+        event = TRY(Event::create(realm, "")); // FIXME: Create CompositionEvent
     } else if (interface_lowercase == "customevent") {
         event = TRY(CustomEvent::create(realm, ""));
     } else if (interface_lowercase == "devicemotionevent") {
-        event = Event::create(realm, ""); // FIXME: Create DeviceMotionEvent
+        event = TRY(Event::create(realm, "")); // FIXME: Create DeviceMotionEvent
     } else if (interface_lowercase == "deviceorientationevent") {
-        event = Event::create(realm, ""); // FIXME: Create DeviceOrientationEvent
+        event = TRY(Event::create(realm, "")); // FIXME: Create DeviceOrientationEvent
     } else if (interface_lowercase == "dragevent") {
-        event = Event::create(realm, ""); // FIXME: Create DragEvent
+        event = TRY(Event::create(realm, "")); // FIXME: Create DragEvent
     } else if (interface_lowercase.is_one_of("event", "events")) {
-        event = Event::create(realm, "");
+        event = TRY(Event::create(realm, ""));
     } else if (interface_lowercase == "focusevent") {
         event = UIEvents::FocusEvent::create(realm, "");
     } else if (interface_lowercase == "hashchangeevent") {
-        event = Event::create(realm, ""); // FIXME: Create HashChangeEvent
+        event = TRY(Event::create(realm, "")); // FIXME: Create HashChangeEvent
     } else if (interface_lowercase == "htmlevents") {
-        event = Event::create(realm, "");
+        event = TRY(Event::create(realm, ""));
     } else if (interface_lowercase == "keyboardevent") {
         event = UIEvents::KeyboardEvent::create(realm, "");
     } else if (interface_lowercase == "messageevent") {
         event = TRY(HTML::MessageEvent::create(realm, ""));
     } else if (interface_lowercase.is_one_of("mouseevent", "mouseevents")) {
-        event = UIEvents::MouseEvent::create(realm, "");
+        event = TRY(UIEvents::MouseEvent::create(realm, ""));
     } else if (interface_lowercase == "storageevent") {
-        event = Event::create(realm, ""); // FIXME: Create StorageEvent
+        event = TRY(Event::create(realm, "")); // FIXME: Create StorageEvent
     } else if (interface_lowercase == "svgevents") {
-        event = Event::create(realm, "");
+        event = TRY(Event::create(realm, ""));
     } else if (interface_lowercase == "textevent") {
-        event = Event::create(realm, ""); // FIXME: Create CompositionEvent
+        event = TRY(Event::create(realm, "")); // FIXME: Create CompositionEvent
     } else if (interface_lowercase == "touchevent") {
-        event = Event::create(realm, ""); // FIXME: Create TouchEvent
+        event = TRY(Event::create(realm, "")); // FIXME: Create TouchEvent
     } else if (interface_lowercase.is_one_of("uievent", "uievents")) {
         event = UIEvents::UIEvent::create(realm, "");
     }
@@ -1539,7 +1539,7 @@ void Document::update_readiness(HTML::DocumentReadyState readiness_value)
     }
 
     // 4. Fire an event named readystatechange at document.
-    dispatch_event(*Event::create(realm(), HTML::EventNames::readystatechange));
+    dispatch_event(Event::create(realm(), HTML::EventNames::readystatechange).release_value_but_fixme_should_propagate_errors());
 }
 
 Page* Document::page()
@@ -1587,7 +1587,7 @@ void Document::completely_finish_loading()
     // 5. Otherwise, if container is non-null, then queue an element task on the DOM manipulation task source given container to fire an event named load at container.
     else if (container) {
         container->queue_an_element_task(HTML::Task::Source::DOMManipulation, [container] {
-            container->dispatch_event(*DOM::Event::create(container->realm(), HTML::EventNames::load));
+            container->dispatch_event(DOM::Event::create(container->realm(), HTML::EventNames::load).release_value_but_fixme_should_propagate_errors());
         });
     }
 }
@@ -1717,7 +1717,7 @@ void Document::update_the_visibility_state(HTML::VisibilityState visibility_stat
     // FIXME: 3. Run any page visibility change steps which may be defined in other specifications, with visibility state and document.
 
     // 4. Fire an event named visibilitychange at document, with its bubbles attribute initialized to true.
-    auto event = DOM::Event::create(realm(), HTML::EventNames::visibilitychange);
+    auto event = DOM::Event::create(realm(), HTML::EventNames::visibilitychange).release_value_but_fixme_should_propagate_errors();
     event->set_bubbles(true);
     dispatch_event(event);
 }
@@ -1738,7 +1738,7 @@ void Document::run_the_resize_steps()
         return;
     m_last_viewport_size = viewport_size;
 
-    window().dispatch_event(*DOM::Event::create(realm(), UIEvents::EventNames::resize));
+    window().dispatch_event(DOM::Event::create(realm(), UIEvents::EventNames::resize).release_value_but_fixme_should_propagate_errors());
 
     schedule_layout_update();
 }
@@ -1750,15 +1750,15 @@ void Document::run_the_scroll_steps()
     for (auto& target : m_pending_scroll_event_targets) {
         // 1. If target is a Document, fire an event named scroll that bubbles at target and fire an event named scroll at the VisualViewport that is associated with target.
         if (is<Document>(*target)) {
-            auto event = DOM::Event::create(realm(), HTML::EventNames::scroll);
+            auto event = DOM::Event::create(realm(), HTML::EventNames::scroll).release_value_but_fixme_should_propagate_errors();
             event->set_bubbles(true);
-            target->dispatch_event(*event);
+            target->dispatch_event(event);
             // FIXME: Fire at the associated VisualViewport
         }
         // 2. Otherwise, fire an event named scroll at target.
         else {
-            auto event = DOM::Event::create(realm(), HTML::EventNames::scroll);
-            target->dispatch_event(*event);
+            auto event = DOM::Event::create(realm(), HTML::EventNames::scroll).release_value_but_fixme_should_propagate_errors();
+            target->dispatch_event(event);
         }
     }
 
@@ -1797,7 +1797,7 @@ void Document::evaluate_media_queries_and_report_changes()
             CSS::MediaQueryListEventInit init;
             init.media = media_query_list->media();
             init.matches = now_matches;
-            auto event = CSS::MediaQueryListEvent::create(realm(), HTML::EventNames::change, init);
+            auto event = CSS::MediaQueryListEvent::create(realm(), HTML::EventNames::change, init).release_value_but_fixme_should_propagate_errors();
             event->set_is_trusted(true);
             media_query_list->dispatch_event(*event);
         }
@@ -2259,7 +2259,7 @@ void Document::unload(bool recursive_flag, Optional<DocumentUnloadTimingInfo> un
         // then fire an event named unload at document's relevant global object, with legacy target override flag set.
         // FIXME: The legacy target override flag is currently set by a virtual override of dispatch_event()
         //        We should reorganize this so that the flag appears explicitly here instead.
-        auto event = DOM::Event::create(realm(), HTML::EventNames::unload);
+        auto event = DOM::Event::create(realm(), HTML::EventNames::unload).release_value_but_fixme_should_propagate_errors();
         global_object().dispatch_event(event);
     }
 

Userland/Libraries/LibWeb/DOM/Event.cpp

@@ -14,12 +14,12 @@
 
 namespace Web::DOM {
 
-JS::NonnullGCPtr<Event> Event::create(JS::Realm& realm, DeprecatedFlyString const& event_name, EventInit const& event_init)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Event>> Event::create(JS::Realm& realm, DeprecatedFlyString const& event_name, EventInit const& event_init)
 {
-    return realm.heap().allocate<Event>(realm, realm, event_name, event_init).release_allocated_value_but_fixme_should_propagate_errors();
+    return MUST_OR_THROW_OOM(realm.heap().allocate<Event>(realm, realm, event_name, event_init));
 }
 
-JS::NonnullGCPtr<Event> Event::construct_impl(JS::Realm& realm, DeprecatedFlyString const& event_name, EventInit const& event_init)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<Event>> Event::construct_impl(JS::Realm& realm, DeprecatedFlyString const& event_name, EventInit const& event_init)
 {
     return create(realm, event_name, event_init);
 }

Userland/Libraries/LibWeb/DOM/Event.h

@@ -45,8 +45,8 @@ public:
 
     using Path = Vector<PathEntry>;
 
-    static JS::NonnullGCPtr<Event> create(JS::Realm&, DeprecatedFlyString const& event_name, EventInit const& event_init = {});
-    static JS::NonnullGCPtr<Event> construct_impl(JS::Realm&, DeprecatedFlyString const& event_name, EventInit const& event_init);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<Event>> create(JS::Realm&, DeprecatedFlyString const& event_name, EventInit const& event_init = {});
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<Event>> construct_impl(JS::Realm&, DeprecatedFlyString const& event_name, EventInit const& event_init);
 
     Event(JS::Realm&, DeprecatedFlyString const& type);
     Event(JS::Realm&, DeprecatedFlyString const& type, EventInit const& event_init);

Userland/Libraries/LibWeb/HTML/BrowsingContext.cpp

@@ -1177,7 +1177,7 @@ WebIDL::ExceptionOr<void> BrowsingContext::traverse_the_history(size_t entry_ind
             // and the newURL attribute initialized to newURL.
 
             // FIXME: Implement a proper HashChangeEvent class.
-            auto event = DOM::Event::create(verify_cast<HTML::Window>(relevant_global_object(*new_document)).realm(), HTML::EventNames::hashchange);
+            auto event = DOM::Event::create(verify_cast<HTML::Window>(relevant_global_object(*new_document)).realm(), HTML::EventNames::hashchange).release_value_but_fixme_should_propagate_errors();
             new_document->dispatch_event(event);
         });
     }

Userland/Libraries/LibWeb/HTML/HTMLElement.cpp

@@ -278,7 +278,7 @@ bool HTMLElement::fire_a_synthetic_pointer_event(DeprecatedFlyString const& type
     // 1. Let event be the result of creating an event using PointerEvent.
     // 2. Initialize event's type attribute to e.
     // FIXME: Actually create a PointerEvent!
-    auto event = UIEvents::MouseEvent::create(realm(), type);
+    auto event = UIEvents::MouseEvent::create(realm(), type).release_value_but_fixme_should_propagate_errors();
 
     // 3. Initialize event's bubbles and cancelable attributes to true.
     event->set_bubbles(true);
@@ -300,7 +300,7 @@ bool HTMLElement::fire_a_synthetic_pointer_event(DeprecatedFlyString const& type
     // FIXME: 8. event's getModifierState() method is to return values appropriately describing the current state of the key input device.
 
     // 9. Return the result of dispatching event at target.
-    return target.dispatch_event(*event);
+    return target.dispatch_event(event);
 }
 
 // https://html.spec.whatwg.org/multipage/interaction.html#dom-click

Userland/Libraries/LibWeb/HTML/HTMLFormElement.cpp

@@ -149,11 +149,11 @@ void HTMLFormElement::submit_form(JS::GCPtr<HTMLElement> submitter, bool from_su
 void HTMLFormElement::reset_form()
 {
     // 1. Let reset be the result of firing an event named reset at form, with the bubbles and cancelable attributes initialized to true.
-    auto reset_event = DOM::Event::create(realm(), HTML::EventNames::reset);
+    auto reset_event = DOM::Event::create(realm(), HTML::EventNames::reset).release_value_but_fixme_should_propagate_errors();
     reset_event->set_bubbles(true);
     reset_event->set_cancelable(true);
 
-    bool reset = dispatch_event(*reset_event);
+    bool reset = dispatch_event(reset_event);
 
     // 2. If reset is true, then invoke the reset algorithm of each resettable element whose form owner is form.
     if (reset) {

Userland/Libraries/LibWeb/HTML/HTMLIFrameElement.cpp

@@ -165,7 +165,7 @@ void run_iframe_load_event_steps(HTML::HTMLIFrameElement& element)
     // FIXME: 4. Set childDocument's iframe load in progress flag.
 
     // 5. Fire an event named load at element.
-    element.dispatch_event(*DOM::Event::create(element.realm(), HTML::EventNames::load));
+    element.dispatch_event(DOM::Event::create(element.realm(), HTML::EventNames::load).release_value_but_fixme_should_propagate_errors());
 
     // FIXME: 6. Unset childDocument's iframe load in progress flag.
 }

Userland/Libraries/LibWeb/HTML/HTMLImageElement.cpp

@@ -27,7 +27,7 @@ HTMLImageElement::HTMLImageElement(DOM::Document& document, DOM::QualifiedName q
         set_needs_style_update(true);
         this->document().set_needs_layout();
         queue_an_element_task(HTML::Task::Source::DOMManipulation, [this] {
-            dispatch_event(*DOM::Event::create(this->realm(), EventNames::load));
+            dispatch_event(DOM::Event::create(this->realm(), EventNames::load).release_value_but_fixme_should_propagate_errors());
         });
     };
 
@@ -36,7 +36,7 @@ HTMLImageElement::HTMLImageElement(DOM::Document& document, DOM::QualifiedName q
         set_needs_style_update(true);
         this->document().set_needs_layout();
         queue_an_element_task(HTML::Task::Source::DOMManipulation, [this] {
-            dispatch_event(*DOM::Event::create(this->realm(), EventNames::error));
+            dispatch_event(DOM::Event::create(this->realm(), EventNames::error).release_value_but_fixme_should_propagate_errors());
         });
     };
 

Userland/Libraries/LibWeb/HTML/HTMLInputElement.cpp

@@ -134,12 +134,12 @@ void HTMLInputElement::update_the_file_selection(JS::NonnullGCPtr<FileAPI::FileL
         this->set_files(files.ptr());
 
         // 2. Fire an event named input at the input element, with the bubbles and composed attributes initialized to true.
-        auto input_event = DOM::Event::create(this->realm(), EventNames::input, { .bubbles = true, .composed = true });
-        this->dispatch_event(*input_event);
+        auto input_event = DOM::Event::create(this->realm(), EventNames::input, { .bubbles = true, .composed = true }).release_value_but_fixme_should_propagate_errors();
+        this->dispatch_event(input_event);
 
         // 3. Fire an event named change at the input element, with the bubbles attribute initialized to true.
-        auto change_event = DOM::Event::create(this->realm(), EventNames::change, { .bubbles = true });
-        this->dispatch_event(*change_event);
+        auto change_event = DOM::Event::create(this->realm(), EventNames::change, { .bubbles = true }).release_value_but_fixme_should_propagate_errors();
+        this->dispatch_event(change_event);
     });
 }
 
@@ -225,13 +225,13 @@ void HTMLInputElement::run_input_activation_behavior()
             return;
 
         // 2. Fire an event named input at the element with the bubbles and composed attributes initialized to true.
-        auto input_event = DOM::Event::create(realm(), HTML::EventNames::input);
+        auto input_event = DOM::Event::create(realm(), HTML::EventNames::input).release_value_but_fixme_should_propagate_errors();
         input_event->set_bubbles(true);
         input_event->set_composed(true);
-        dispatch_event(*input_event);
+        dispatch_event(input_event);
 
         // 3. Fire an event named change at the element with the bubbles attribute initialized to true.
-        auto change_event = DOM::Event::create(realm(), HTML::EventNames::change);
+        auto change_event = DOM::Event::create(realm(), HTML::EventNames::change).release_value_but_fixme_should_propagate_errors();
         change_event->set_bubbles(true);
         dispatch_event(*change_event);
     } else if (type_state() == TypeAttributeState::SubmitButton) {
@@ -249,7 +249,7 @@ void HTMLInputElement::run_input_activation_behavior()
     } else if (type_state() == TypeAttributeState::FileUpload) {
         show_the_picker_if_applicable(*this);
     } else {
-        dispatch_event(*DOM::Event::create(realm(), EventNames::change));
+        dispatch_event(DOM::Event::create(realm(), EventNames::change).release_value_but_fixme_should_propagate_errors());
     }
 }
 
@@ -262,15 +262,15 @@ void HTMLInputElement::did_edit_text_node(Badge<BrowsingContext>)
     // NOTE: This is a bit ad-hoc, but basically implements part of "4.10.5.5 Common event behaviors"
     //       https://html.spec.whatwg.org/multipage/input.html#common-input-element-events
     queue_an_element_task(HTML::Task::Source::UserInteraction, [this] {
-        auto input_event = DOM::Event::create(realm(), HTML::EventNames::input);
+        auto input_event = DOM::Event::create(realm(), HTML::EventNames::input).release_value_but_fixme_should_propagate_errors();
         input_event->set_bubbles(true);
         input_event->set_composed(true);
         dispatch_event(*input_event);
 
         // FIXME: This should only fire when the input is "committed", whatever that means.
-        auto change_event = DOM::Event::create(realm(), HTML::EventNames::change);
+        auto change_event = DOM::Event::create(realm(), HTML::EventNames::change).release_value_but_fixme_should_propagate_errors();
         change_event->set_bubbles(true);
-        dispatch_event(*change_event);
+        dispatch_event(change_event);
     });
 }
 

Userland/Libraries/LibWeb/HTML/HTMLObjectElement.cpp

@@ -124,7 +124,7 @@ void HTMLObjectElement::queue_element_task_to_run_object_representation_steps()
 
             // 3. If that failed, fire an event named error at the element, then jump to the step below labeled fallback.
             if (!url.is_valid()) {
-                dispatch_event(*DOM::Event::create(realm(), HTML::EventNames::error));
+                dispatch_event(DOM::Event::create(realm(), HTML::EventNames::error).release_value_but_fixme_should_propagate_errors());
                 return run_object_representation_fallback_steps();
             }
 
@@ -151,7 +151,7 @@ void HTMLObjectElement::queue_element_task_to_run_object_representation_steps()
 void HTMLObjectElement::resource_did_fail()
 {
     // 4.7. If the load failed (e.g. there was an HTTP 404 error, there was a DNS error), fire an event named error at the element, then jump to the step below labeled fallback.
-    dispatch_event(*DOM::Event::create(realm(), HTML::EventNames::error));
+    dispatch_event(DOM::Event::create(realm(), HTML::EventNames::error).release_value_but_fixme_should_propagate_errors());
     run_object_representation_fallback_steps();
 }
 
@@ -289,7 +289,7 @@ void HTMLObjectElement::run_object_representation_completed_steps(Representation
     // 4.11. If the object element does not represent its nested browsing context, then once the resource is completely loaded, queue an element task on the DOM manipulation task source given the object element to fire an event named load at the element.
     if (representation != Representation::NestedBrowsingContext) {
         queue_an_element_task(HTML::Task::Source::DOMManipulation, [&]() {
-            dispatch_event(*DOM::Event::create(realm(), HTML::EventNames::load));
+            dispatch_event(DOM::Event::create(realm(), HTML::EventNames::load).release_value_but_fixme_should_propagate_errors());
         });
     }
 

Userland/Libraries/LibWeb/HTML/HTMLScriptElement.cpp

@@ -71,7 +71,7 @@ void HTMLScriptElement::execute_script()
     // 3. If el's result is null, then fire an event named error at el, and return.
     if (m_result.has<ResultState::Null>()) {
         dbgln("HTMLScriptElement: Refusing to run script because the element's result is null.");
-        dispatch_event(*DOM::Event::create(realm(), HTML::EventNames::error));
+        dispatch_event(DOM::Event::create(realm(), HTML::EventNames::error).release_value_but_fixme_should_propagate_errors());
         return;
     }
 
@@ -122,7 +122,7 @@ void HTMLScriptElement::execute_script()
 
     // 8. If el's from an external file is true, then fire an event named load at el.
     if (m_from_an_external_file)
-        dispatch_event(*DOM::Event::create(realm(), HTML::EventNames::load));
+        dispatch_event(DOM::Event::create(realm(), HTML::EventNames::load).release_value_but_fixme_should_propagate_errors());
 }
 
 // https://html.spec.whatwg.org/multipage/scripting.html#prepare-a-script
@@ -292,7 +292,7 @@ void HTMLScriptElement::prepare_script()
         if (m_script_type == ScriptType::ImportMap) {
             // then queue an element task on the DOM manipulation task source given el to fire an event named error at el, and return.
             queue_an_element_task(HTML::Task::Source::DOMManipulation, [this] {
-                dispatch_event(*DOM::Event::create(realm(), HTML::EventNames::error));
+                dispatch_event(DOM::Event::create(realm(), HTML::EventNames::error).release_value_but_fixme_should_propagate_errors());
             });
             return;
         }
@@ -304,7 +304,7 @@ void HTMLScriptElement::prepare_script()
         if (src.is_empty()) {
             dbgln("HTMLScriptElement: Refusing to run script because the src attribute is empty.");
             queue_an_element_task(HTML::Task::Source::DOMManipulation, [this] {
-                dispatch_event(*DOM::Event::create(realm(), HTML::EventNames::error));
+                dispatch_event(DOM::Event::create(realm(), HTML::EventNames::error).release_value_but_fixme_should_propagate_errors());
             });
             return;
         }
@@ -319,7 +319,7 @@ void HTMLScriptElement::prepare_script()
         if (!url.is_valid()) {
             dbgln("HTMLScriptElement: Refusing to run script because the src URL '{}' is invalid.", url);
             queue_an_element_task(HTML::Task::Source::DOMManipulation, [this] {
-                dispatch_event(*DOM::Event::create(realm(), HTML::EventNames::error));
+                dispatch_event(DOM::Event::create(realm(), HTML::EventNames::error).release_value_but_fixme_should_propagate_errors());
             });
             return;
         }

Userland/Libraries/LibWeb/HTML/Parser/HTMLParser.cpp

@@ -253,9 +253,9 @@ void HTMLParser::the_end()
         document->load_timing_info().dom_content_loaded_event_start_time = HighResolutionTime::unsafe_shared_current_time();
 
         // 2. Fire an event named DOMContentLoaded at the Document object, with its bubbles attribute initialized to true.
-        auto content_loaded_event = DOM::Event::create(document->realm(), HTML::EventNames::DOMContentLoaded);
+        auto content_loaded_event = DOM::Event::create(document->realm(), HTML::EventNames::DOMContentLoaded).release_value_but_fixme_should_propagate_errors();
         content_loaded_event->set_bubbles(true);
-        document->dispatch_event(*content_loaded_event);
+        document->dispatch_event(content_loaded_event);
 
         // 3. Set the Document's load timing info's DOM content loaded event end time to the current high resolution time given the Document's relevant global object.
         document->load_timing_info().dom_content_loaded_event_end_time = HighResolutionTime::unsafe_shared_current_time();
@@ -294,7 +294,7 @@ void HTMLParser::the_end()
         // 5. Fire an event named load at window, with legacy target override flag set.
         // FIXME: The legacy target override flag is currently set by a virtual override of dispatch_event()
         //        We should reorganize this so that the flag appears explicitly here instead.
-        window->dispatch_event(*DOM::Event::create(document->realm(), HTML::EventNames::load));
+        window->dispatch_event(DOM::Event::create(document->realm(), HTML::EventNames::load).release_value_but_fixme_should_propagate_errors());
 
         // FIXME: 6. Invoke WebDriver BiDi load complete with the Document's browsing context, and a new WebDriver BiDi navigation status whose id is the Document object's navigation id, status is "complete", and url is the Document object's URL.
 

Userland/Libraries/LibWeb/Page/EventHandler.cpp

@@ -249,12 +249,12 @@ bool EventHandler::handle_mouseup(CSSPixelPoint position, unsigned button, unsig
             auto offset = compute_mouse_event_offset(position, *layout_node);
             auto client_offset = compute_mouse_event_client_offset(position);
             auto page_offset = compute_mouse_event_page_offset(client_offset);
-            node->dispatch_event(*UIEvents::MouseEvent::create_from_platform_event(node->realm(), UIEvents::EventNames::mouseup, offset, client_offset, page_offset, buttons, button));
+            node->dispatch_event(UIEvents::MouseEvent::create_from_platform_event(node->realm(), UIEvents::EventNames::mouseup, offset, client_offset, page_offset, buttons, button).release_value_but_fixme_should_propagate_errors());
             handled_event = true;
 
             bool run_activation_behavior = true;
             if (node.ptr() == m_mousedown_target && button == GUI::MouseButton::Primary) {
-                run_activation_behavior = node->dispatch_event(*UIEvents::MouseEvent::create_from_platform_event(node->realm(), UIEvents::EventNames::click, offset, client_offset, page_offset, button));
+                run_activation_behavior = node->dispatch_event(UIEvents::MouseEvent::create_from_platform_event(node->realm(), UIEvents::EventNames::click, offset, client_offset, page_offset, button).release_value_but_fixme_should_propagate_errors());
             }
 
             if (run_activation_behavior) {
@@ -372,7 +372,7 @@ bool EventHandler::handle_mousedown(CSSPixelPoint position, unsigned button, uns
         auto offset = compute_mouse_event_offset(position, *layout_node);
         auto client_offset = compute_mouse_event_client_offset(position);
         auto page_offset = compute_mouse_event_page_offset(client_offset);
-        node->dispatch_event(*UIEvents::MouseEvent::create_from_platform_event(node->realm(), UIEvents::EventNames::mousedown, offset, client_offset, page_offset, buttons, button));
+        node->dispatch_event(UIEvents::MouseEvent::create_from_platform_event(node->realm(), UIEvents::EventNames::mousedown, offset, client_offset, page_offset, buttons, button).release_value_but_fixme_should_propagate_errors());
     }
 
     // NOTE: Dispatching an event may have disturbed the world.
@@ -488,7 +488,7 @@ bool EventHandler::handle_mousemove(CSSPixelPoint position, unsigned buttons, un
             auto offset = compute_mouse_event_offset(position, *layout_node);
             auto client_offset = compute_mouse_event_client_offset(position);
             auto page_offset = compute_mouse_event_page_offset(client_offset);
-            node->dispatch_event(*UIEvents::MouseEvent::create_from_platform_event(node->realm(), UIEvents::EventNames::mousemove, offset, client_offset, page_offset, buttons));
+            node->dispatch_event(UIEvents::MouseEvent::create_from_platform_event(node->realm(), UIEvents::EventNames::mousemove, offset, client_offset, page_offset, buttons).release_value_but_fixme_should_propagate_errors());
             // NOTE: Dispatching an event may have disturbed the world.
             if (!paint_root() || paint_root() != node->document().paint_box())
                 return true;
@@ -577,7 +577,7 @@ bool EventHandler::handle_doubleclick(CSSPixelPoint position, unsigned button, u
     auto offset = compute_mouse_event_offset(position, *layout_node);
     auto client_offset = compute_mouse_event_client_offset(position);
     auto page_offset = compute_mouse_event_page_offset(client_offset);
-    node->dispatch_event(*UIEvents::MouseEvent::create_from_platform_event(node->realm(), UIEvents::EventNames::dblclick, offset, client_offset, page_offset, buttons, button));
+    node->dispatch_event(UIEvents::MouseEvent::create_from_platform_event(node->realm(), UIEvents::EventNames::dblclick, offset, client_offset, page_offset, buttons, button).release_value_but_fixme_should_propagate_errors());
 
     // NOTE: Dispatching an event may have disturbed the world.
     if (!paint_root() || paint_root() != node->document().paint_box())

Userland/Libraries/LibWeb/UIEvents/MouseEvent.cpp

@@ -56,12 +56,12 @@ static i16 determine_button(unsigned mouse_button)
     }
 }
 
-MouseEvent* MouseEvent::create(JS::Realm& realm, DeprecatedFlyString const& event_name, MouseEventInit const& event_init)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<MouseEvent>> MouseEvent::create(JS::Realm& realm, DeprecatedFlyString const& event_name, MouseEventInit const& event_init)
 {
-    return realm.heap().allocate<MouseEvent>(realm, realm, event_name, event_init).release_allocated_value_but_fixme_should_propagate_errors();
+    return MUST_OR_THROW_OOM(realm.heap().allocate<MouseEvent>(realm, realm, event_name, event_init));
 }
 
-MouseEvent* MouseEvent::create_from_platform_event(JS::Realm& realm, DeprecatedFlyString const& event_name, CSSPixelPoint offset, CSSPixelPoint client_offset, CSSPixelPoint page_offset, unsigned buttons, unsigned mouse_button)
+WebIDL::ExceptionOr<JS::NonnullGCPtr<MouseEvent>> MouseEvent::create_from_platform_event(JS::Realm& realm, DeprecatedFlyString const& event_name, CSSPixelPoint offset, CSSPixelPoint client_offset, CSSPixelPoint page_offset, unsigned buttons, unsigned mouse_button)
 {
     MouseEventInit event_init {};
     event_init.offset_x = static_cast<double>(offset.x().value());

Userland/Libraries/LibWeb/UIEvents/MouseEvent.h

@@ -29,8 +29,8 @@ class MouseEvent : public UIEvent {
     WEB_PLATFORM_OBJECT(MouseEvent, UIEvent);
 
 public:
-    static MouseEvent* create(JS::Realm&, DeprecatedFlyString const& event_name, MouseEventInit const& event_init = {});
-    static MouseEvent* create_from_platform_event(JS::Realm&, DeprecatedFlyString const& event_name, CSSPixelPoint offset, CSSPixelPoint client_offset, CSSPixelPoint page_offset, unsigned buttons, unsigned mouse_button = 1);
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<MouseEvent>> create(JS::Realm&, DeprecatedFlyString const& event_name, MouseEventInit const& event_init = {});
+    static WebIDL::ExceptionOr<JS::NonnullGCPtr<MouseEvent>> create_from_platform_event(JS::Realm&, DeprecatedFlyString const& event_name, CSSPixelPoint offset, CSSPixelPoint client_offset, CSSPixelPoint page_offset, unsigned buttons, unsigned mouse_button = 1);
 
     virtual ~MouseEvent() override;
 

Userland/Libraries/LibWeb/WebSockets/WebSocket.cpp

@@ -204,13 +204,13 @@ void WebSocket::on_open()
     // 1. Change the readyState attribute's value to OPEN (1).
     // 2. Change the extensions attribute's value to the extensions in use, if it is not the null value. [WSP]
     // 3. Change the protocol attribute's value to the subprotocol in use, if it is not the null value. [WSP]
-    dispatch_event(*DOM::Event::create(realm(), HTML::EventNames::open));
+    dispatch_event(DOM::Event::create(realm(), HTML::EventNames::open).release_value_but_fixme_should_propagate_errors());
 }
 
 // https://websockets.spec.whatwg.org/#feedback-from-the-protocol
 void WebSocket::on_error()
 {
-    dispatch_event(*DOM::Event::create(realm(), HTML::EventNames::error));
+    dispatch_event(DOM::Event::create(realm(), HTML::EventNames::error).release_value_but_fixme_should_propagate_errors());
 }
 
 // https://websockets.spec.whatwg.org/#feedback-from-the-protocol

Userland/Libraries/LibWeb/XHR/XMLHttpRequest.cpp

@@ -419,7 +419,7 @@ WebIDL::ExceptionOr<void> XMLHttpRequest::open(DeprecatedString const& method_st
         m_state = State::Opened;
 
         // 2. Fire an event named readystatechange at this.
-        dispatch_event(*DOM::Event::create(realm(), EventNames::readystatechange));
+        dispatch_event(TRY(DOM::Event::create(realm(), EventNames::readystatechange)));
     }
 
     return {};
@@ -463,8 +463,8 @@ WebIDL::ExceptionOr<void> XMLHttpRequest::send(Optional<DocumentOrXMLHttpRequest
     if (should_enforce_same_origin_policy && !m_window->associated_document().origin().is_same_origin(request_url_origin)) {
         dbgln("XHR failed to load: Same-Origin Policy violation: {} may not load {}", m_window->associated_document().url(), request_url);
         m_state = State::Done;
-        dispatch_event(*DOM::Event::create(realm, EventNames::readystatechange));
-        dispatch_event(*DOM::Event::create(realm, HTML::EventNames::error));
+        dispatch_event(TRY(DOM::Event::create(realm, EventNames::readystatechange)));
+        dispatch_event(TRY(DOM::Event::create(realm, HTML::EventNames::error)));
         return {};
     }
 
@@ -544,7 +544,7 @@ WebIDL::ExceptionOr<void> XMLHttpRequest::send(Optional<DocumentOrXMLHttpRequest
                 xhr.m_status = status_code.value_or(0);
                 xhr.m_response_headers = move(response_headers);
                 xhr.m_send = false;
-                xhr.dispatch_event(*DOM::Event::create(xhr.realm(), EventNames::readystatechange));
+                xhr.dispatch_event(DOM::Event::create(xhr.realm(), EventNames::readystatechange).release_value_but_fixme_should_propagate_errors());
                 xhr.fire_progress_event(EventNames::load, transmitted, length);
                 xhr.fire_progress_event(EventNames::loadend, transmitted, length);
             },
@@ -556,8 +556,8 @@ WebIDL::ExceptionOr<void> XMLHttpRequest::send(Optional<DocumentOrXMLHttpRequest
                 auto& xhr = const_cast<XMLHttpRequest&>(*strong_this);
                 xhr.m_state = State::Done;
                 xhr.set_status(status_code.value_or(0));
-                xhr.dispatch_event(*DOM::Event::create(xhr.realm(), EventNames::readystatechange));
-                xhr.dispatch_event(*DOM::Event::create(xhr.realm(), HTML::EventNames::error));
+                xhr.dispatch_event(DOM::Event::create(xhr.realm(), EventNames::readystatechange).release_value_but_fixme_should_propagate_errors());
+                xhr.dispatch_event(DOM::Event::create(xhr.realm(), HTML::EventNames::error).release_value_but_fixme_should_propagate_errors());
             },
             m_timeout,
             [weak_this = make_weak_ptr<XMLHttpRequest>()] {
@@ -565,7 +565,7 @@ WebIDL::ExceptionOr<void> XMLHttpRequest::send(Optional<DocumentOrXMLHttpRequest
                 if (!strong_this)
                     return;
                 auto& xhr = const_cast<XMLHttpRequest&>(*strong_this);
-                xhr.dispatch_event(*DOM::Event::create(xhr.realm(), EventNames::timeout));
+                xhr.dispatch_event(DOM::Event::create(xhr.realm(), EventNames::timeout).release_value_but_fixme_should_propagate_errors());
             });
     } else {
         TODO();

Userland/Libraries/LibWeb/XML/XMLDocumentBuilder.cpp

@@ -189,9 +189,9 @@ void XMLDocumentBuilder::document_end()
         document->load_timing_info().dom_content_loaded_event_start_time = HighResolutionTime::unsafe_shared_current_time();
 
         // Fire an event named DOMContentLoaded at the Document object, with its bubbles attribute initialized to true.
-        auto content_loaded_event = DOM::Event::create(document->realm(), HTML::EventNames::DOMContentLoaded);
+        auto content_loaded_event = DOM::Event::create(document->realm(), HTML::EventNames::DOMContentLoaded).release_value_but_fixme_should_propagate_errors();
         content_loaded_event->set_bubbles(true);
-        document->dispatch_event(*content_loaded_event);
+        document->dispatch_event(content_loaded_event);
 
         // Set the Document's load timing info's DOM content loaded event end time to the current high resolution time given the Document's relevant global object.
         document->load_timing_info().dom_content_loaded_event_end_time = HighResolutionTime::unsafe_shared_current_time();
@@ -229,7 +229,7 @@ void XMLDocumentBuilder::document_end()
         // Fire an event named load at window, with legacy target override flag set.
         // FIXME: The legacy target override flag is currently set by a virtual override of dispatch_event()
         // We should reorganize this so that the flag appears explicitly here instead.
-        window->dispatch_event(*DOM::Event::create(document->realm(), HTML::EventNames::load));
+        window->dispatch_event(DOM::Event::create(document->realm(), HTML::EventNames::load).release_value_but_fixme_should_propagate_errors());
 
         // FIXME: Invoke WebDriver BiDi load complete with the Document's browsing context, and a new WebDriver BiDi navigation status whose id is the Document object's navigation id, status is "complete", and url is the Document object's URL.
 

Userland/Services/WebContent/WebDriverConnection.cpp

@@ -314,8 +314,8 @@ static bool fire_an_event(DeprecatedString name, Optional<Web::DOM::Element&> ta
     if (!target.has_value())
         return false;
 
-    auto event = T::create(target->realm(), name);
-    return target->dispatch_event(*event);
+    auto event = T::create(target->realm(), name).release_value_but_fixme_should_propagate_errors();
+    return target->dispatch_event(event);
 }
 
 ErrorOr<NonnullRefPtr<WebDriverConnection>> WebDriverConnection::connect(Web::PageClient& page_client, DeprecatedString const& webdriver_ipc_path)