LibWeb/Fetch: Deserialize abort reason

Deserialize the fetch controllers abort reason according to the spec.
Currently fetch does not support a scenario where this actually happens.

Libraries/LibWeb/Fetch/FetchMethod.cpp

@@ -73,14 +73,14 @@ GC::Ref<WebIDL::Promise> fetch(JS::VM& vm, RequestInfo const& input, RequestInit
     auto locally_aborted = Fetching::RefCountedFlag::create(false);
 
     // 10. Let controller be null.
-    GC::Ptr<Infrastructure::FetchController> controller;
+    auto controller_holder = Infrastructure::FetchControllerHolder::create(vm);
 
     // NOTE: Step 11 is done out of order so that the controller is non-null when we capture the GCPtr by copy in the abort algorithm lambda.
     //       This is not observable, AFAICT.
 
     // 12. Set controller to the result of calling fetch given request and processResponse given response being these
     //     steps:
-    auto process_response = [locally_aborted, promise_capability, request, response_object, &relevant_realm](GC::Ref<Infrastructure::Response> response) mutable {
+    auto process_response = [locally_aborted, promise_capability, request, response_object, controller_holder, &relevant_realm](GC::Ref<Infrastructure::Response> response) mutable {
         // 1. If locallyAborted is true, then abort these steps.
         if (locally_aborted->value())
             return;
@@ -90,9 +90,9 @@ GC::Ref<WebIDL::Promise> fetch(JS::VM& vm, RequestInfo const& input, RequestInit
 
         // 2. If response’s aborted flag is set, then:
         if (response->aborted()) {
-            // FIXME: 1. Let deserializedError be the result of deserialize a serialized abort reason given controller’s
+            // 1. Let deserializedError be the result of deserialize a serialized abort reason given controller’s
             //    serialized abort reason and relevantRealm.
-            auto deserialized_error = JS::js_undefined();
+            auto deserialized_error = controller_holder->controller()->deserialize_a_serialized_abort_reason(relevant_realm);
 
             // 2. Abort the fetch() call with p, request, responseObject, and deserializedError.
             abort_fetch(relevant_realm, promise_capability, request, response_object, deserialized_error);
@@ -115,7 +115,7 @@ GC::Ref<WebIDL::Promise> fetch(JS::VM& vm, RequestInfo const& input, RequestInit
         // 5. Resolve p with responseObject.
         WebIDL::resolve_promise(relevant_realm, promise_capability, response_object);
     };
-    controller = MUST(Fetching::fetch(
+    controller_holder->set_controller(MUST(Fetching::fetch(
         realm,
         request,
         Infrastructure::FetchAlgorithms::create(vm,
@@ -126,20 +126,20 @@ GC::Ref<WebIDL::Promise> fetch(JS::VM& vm, RequestInfo const& input, RequestInit
                 .process_response = move(process_response),
                 .process_response_end_of_body = {},
                 .process_response_consume_body = {},
-            })));
+            }))));
 
     // 11. Add the following abort steps to requestObject’s signal:
-    request_object->signal()->add_abort_algorithm([locally_aborted, request, controller, promise_capability, request_object, response_object, &relevant_realm] {
+    request_object->signal()->add_abort_algorithm([locally_aborted, request, controller_holder, promise_capability, request_object, response_object, &relevant_realm] {
         dbgln_if(WEB_FETCH_DEBUG, "Fetch: Request object signal's abort algorithm called");
 
         // 1. Set locallyAborted to true.
         locally_aborted->set_value(true);
 
         // 2. Assert: controller is non-null.
-        VERIFY(controller);
+        VERIFY(controller_holder->controller());
 
         // 3. Abort controller with requestObject’s signal’s abort reason.
-        controller->abort(relevant_realm, request_object->signal()->reason());
+        controller_holder->controller()->abort(relevant_realm, request_object->signal()->reason());
 
         // AD-HOC: An execution context is required for Promise functions.
         HTML::TemporaryExecutionContext execution_context { relevant_realm };

Libraries/LibWeb/Fetch/Infrastructure/FetchController.cpp

@@ -96,7 +96,27 @@ void FetchController::abort(JS::Realm& realm, Optional<JS::Value> error)
     m_serialized_abort_reason = structured_serialize(realm.vm(), error.value(), fallback_error);
 }
 
-// FIXME: https://fetch.spec.whatwg.org/#deserialize-a-serialized-abort-reason
+// https://fetch.spec.whatwg.org/#deserialize-a-serialized-abort-reason
+JS::Value FetchController::deserialize_a_serialized_abort_reason(JS::Realm& realm)
+{
+    // 1. Let fallbackError be an "AbortError" DOMException.
+    auto fallback_error = WebIDL::AbortError::create(realm, "Fetch was aborted"_string);
+
+    // 2. Let deserializedError be fallbackError.
+    JS::Value deserialized_error = fallback_error;
+
+    // 3. If abortReason is non-null, then set deserializedError to StructuredDeserialize(abortReason, realm).
+    //    If that threw an exception or returned undefined, then set deserializedError to fallbackError.
+    if (m_serialized_abort_reason.has_value()) {
+        auto deserialized_error_or_exception = HTML::structured_deserialize(realm.vm(), m_serialized_abort_reason.value(), realm, {});
+        if (!deserialized_error_or_exception.is_exception() && !deserialized_error_or_exception.value().is_undefined()) {
+            deserialized_error = deserialized_error_or_exception.value();
+        }
+    }
+
+    // 4. Return deserializedError.
+    return deserialized_error;
+}
 
 // https://fetch.spec.whatwg.org/#fetch-controller-terminate
 void FetchController::terminate()
@@ -137,4 +157,19 @@ void FetchController::fetch_task_complete(u64 fetch_task_id)
     m_ongoing_fetch_tasks.remove(fetch_task_id);
 }
 
+GC_DEFINE_ALLOCATOR(FetchControllerHolder);
+
+FetchControllerHolder::FetchControllerHolder() = default;
+
+GC::Ref<FetchControllerHolder> FetchControllerHolder::create(JS::VM& vm)
+{
+    return vm.heap().allocate<FetchControllerHolder>();
+}
+
+void FetchControllerHolder::visit_edges(JS::Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_controller);
+}
+
 }

Libraries/LibWeb/Fetch/Infrastructure/FetchController.h

@@ -44,6 +44,7 @@ public:
     void process_next_manual_redirect() const;
     [[nodiscard]] GC::Ref<FetchTimingInfo> extract_full_timing_info() const;
     void abort(JS::Realm&, Optional<JS::Value>);
+    JS::Value deserialize_a_serialized_abort_reason(JS::Realm&);
     void terminate();
 
     void set_fetch_params(Badge<FetchParams>, GC::Ref<FetchParams> fetch_params) { m_fetch_params = fetch_params; }
@@ -77,7 +78,7 @@ private:
     // https://fetch.spec.whatwg.org/#fetch-controller-report-timing-steps
     // serialized abort reason (default null)
     //     Null or a Record (result of StructuredSerialize).
-    HTML::SerializationRecord m_serialized_abort_reason;
+    Optional<HTML::SerializationRecord> m_serialized_abort_reason;
 
     // https://fetch.spec.whatwg.org/#fetch-controller-next-manual-redirect-steps
     // next manual redirect steps (default null)
@@ -90,4 +91,22 @@ private:
     u64 m_next_fetch_task_id { 0 };
 };
 
+class FetchControllerHolder : public JS::Cell {
+    GC_CELL(FetchControllerHolder, JS::Cell);
+    GC_DECLARE_ALLOCATOR(FetchControllerHolder);
+
+public:
+    static GC::Ref<FetchControllerHolder> create(JS::VM&);
+
+    [[nodiscard]] GC::Ptr<FetchController> const& controller() const { return m_controller; }
+    void set_controller(GC::Ref<FetchController> controller) { m_controller = controller; }
+
+private:
+    FetchControllerHolder();
+
+    virtual void visit_edges(Cell::Visitor&) override;
+
+    GC::Ptr<FetchController> m_controller;
+};
+
 }