LibWeb: Support removing callbacks from AbortSignal

This will be needed by Streams. To support this, we now store callbacks
in a hash table, keyed by an ID. Callers may use that ID to remove the
callback at a later point.

Libraries/LibWeb/DOM/AbortSignal.cpp

@@ -35,14 +35,22 @@ void AbortSignal::initialize(JS::Realm& realm)
 }
 
 // https://dom.spec.whatwg.org/#abortsignal-add
-void AbortSignal::add_abort_algorithm(Function<void()> abort_algorithm)
+Optional<AbortSignal::AbortAlgorithmID> AbortSignal::add_abort_algorithm(Function<void()> abort_algorithm)
 {
     // 1. If signal is aborted, then return.
     if (aborted())
-        return;
+        return {};
 
     // 2. Append algorithm to signal’s abort algorithms.
-    m_abort_algorithms.append(GC::create_function(vm().heap(), move(abort_algorithm)));
+    m_abort_algorithms.set(++m_next_abort_algorithm_id, GC::create_function(vm().heap(), move(abort_algorithm)));
+    return m_next_abort_algorithm_id;
+}
+
+// https://dom.spec.whatwg.org/#abortsignal-remove
+void AbortSignal::remove_abort_algorithm(AbortAlgorithmID id)
+{
+    // To remove an algorithm algorithm from an AbortSignal signal, remove algorithm from signal’s abort algorithms.
+    m_abort_algorithms.remove(id);
 }
 
 // https://dom.spec.whatwg.org/#abortsignal-signal-abort
@@ -76,8 +84,8 @@ void AbortSignal::signal_abort(JS::Value reason)
     // https://dom.spec.whatwg.org/#run-the-abort-steps
     auto run_the_abort_steps = [](auto& signal) {
         // 1. For each algorithm in signal’s abort algorithms: run algorithm.
-        for (auto& algorithm : signal.m_abort_algorithms)
+        for (auto const& algorithm : signal.m_abort_algorithms)
-            algorithm->function()();
+            algorithm.value->function()();
 
         // 2. Empty signal’s abort algorithms.
         signal.m_abort_algorithms.clear();

Libraries/LibWeb/DOM/AbortSignal.h

@@ -7,6 +7,7 @@
 
 #pragma once
 
+#include <AK/HashMap.h>
 #include <AK/RefCounted.h>
 #include <AK/Weakable.h>
 #include <LibGC/Function.h>
@@ -26,7 +27,9 @@ public:
 
     virtual ~AbortSignal() override = default;
 
-    void add_abort_algorithm(ESCAPING Function<void()>);
+    using AbortAlgorithmID = u64;
+    Optional<AbortAlgorithmID> add_abort_algorithm(Function<void()>);
+    void remove_abort_algorithm(AbortAlgorithmID);
 
     // https://dom.spec.whatwg.org/#dom-abortsignal-aborted
     // An AbortSignal object is aborted when its abort reason is not undefined.
@@ -68,8 +71,8 @@ private:
     JS::Value m_abort_reason { JS::js_undefined() };
 
     // https://dom.spec.whatwg.org/#abortsignal-abort-algorithms
-    // FIXME: This should be a set.
+    OrderedHashMap<AbortAlgorithmID, GC::Ref<GC::Function<void()>>> m_abort_algorithms;
-    Vector<GC::Ref<GC::Function<void()>>> m_abort_algorithms;
+    AbortAlgorithmID m_next_abort_algorithm_id { 0 };
 
     // https://dom.spec.whatwg.org/#abortsignal-source-signals
     // An AbortSignal object has associated source signals (a weak set of AbortSignal objects that the object is dependent on for its aborted state), which is initially empty.

Libraries/LibWeb/DOM/EventTarget.cpp

@@ -231,7 +231,7 @@ void EventTarget::add_an_event_listener(DOMEventListener& listener)
     // 6. If listener’s signal is not null, then add the following abort steps to it:
     if (listener.signal) {
         // NOTE: `this` and `listener` are protected by AbortSignal using GC::HeapFunction.
-        listener.signal->add_abort_algorithm([this, &listener] {
+        (void)listener.signal->add_abort_algorithm([this, &listener] {
             // 1. Remove an event listener with eventTarget and listener.
             remove_an_event_listener(listener);
         });

Libraries/LibWeb/Fetch/FetchMethod.cpp

@@ -130,7 +130,7 @@ GC::Ref<WebIDL::Promise> fetch(JS::VM& vm, RequestInfo const& input, RequestInit
             }))));
 
     // 11. Add the following abort steps to requestObject’s signal:
-    request_object->signal()->add_abort_algorithm([locally_aborted, request, controller_holder, promise_capability, request_object, response_object, &relevant_realm] {
+    (void)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.

Libraries/LibWeb/HTML/CloseWatcher.cpp

@@ -65,7 +65,7 @@ WebIDL::ExceptionOr<GC::Ref<CloseWatcher>> CloseWatcher::construct_impl(JS::Real
         }
 
         // 3.2 Add the following steps to options["signal"]:
-        signal->add_abort_algorithm([close_watcher] {
+        (void)signal->add_abort_algorithm([close_watcher] {
             // 3.2.1 Destroy closeWatcher.
             close_watcher->destroy();
         });