LibWeb: Add initial support for AbortController and AbortSignal

The DOM specification says that the primary use case for these is to
give Promises abort semantics. It is also a prerequisite for Fetch,
as it is used to make Fetch abortable.
a

Userland/Libraries/LibWeb/DOM/AbortController.cpp

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/DOM/AbortController.h>
+#include <LibWeb/DOM/AbortSignal.h>
+
+namespace Web::DOM {
+
+// https://dom.spec.whatwg.org/#dom-abortcontroller-abortcontroller
+AbortController::AbortController(Document& document)
+    : m_signal(AbortSignal::create(document))
+{
+}
+
+AbortController::~AbortController()
+{
+}
+
+// https://dom.spec.whatwg.org/#dom-abortcontroller-abort
+void AbortController::abort()
+{
+    m_signal->signal_abort();
+}
+
+}

Userland/Libraries/LibWeb/DOM/AbortController.h

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+/*
+ * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/RefCounted.h>
+#include <AK/Weakable.h>
+#include <LibWeb/Bindings/WindowObject.h>
+#include <LibWeb/Bindings/Wrappable.h>
+#include <LibWeb/DOM/AbortSignal.h>
+#include <LibWeb/DOM/Window.h>
+#include <LibWeb/Forward.h>
+
+namespace Web::DOM {
+
+// https://dom.spec.whatwg.org/#abortcontroller
+class AbortController final
+    : public RefCounted<AbortController>
+    , public Weakable<AbortController>
+    , public Bindings::Wrappable {
+public:
+    using WrapperType = Bindings::AbortControllerWrapper;
+
+    static NonnullRefPtr<AbortController> create(Document& document)
+    {
+        return adopt_ref(*new AbortController(document));
+    }
+
+    static NonnullRefPtr<AbortController> create_with_global_object(Bindings::WindowObject& window_object)
+    {
+        return AbortController::create(window_object.impl().document());
+    }
+
+    virtual ~AbortController() override;
+
+    // https://dom.spec.whatwg.org/#dom-abortcontroller-signal
+    NonnullRefPtr<AbortSignal> signal() const { return m_signal; }
+
+    void abort();
+
+private:
+    AbortController(Document& document);
+
+    // https://dom.spec.whatwg.org/#abortcontroller-signal
+    NonnullRefPtr<AbortSignal> m_signal;
+};
+
+}

Userland/Libraries/LibWeb/DOM/AbortController.idl

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+[Exposed=(Window,Worker)]
+interface AbortController {
+    constructor();
+
+    [SameObject] readonly attribute AbortSignal signal;
+
+    undefined abort();
+};

Userland/Libraries/LibWeb/DOM/AbortSignal.cpp

@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibWeb/Bindings/AbortSignalWrapper.h>
+#include <LibWeb/DOM/AbortSignal.h>
+#include <LibWeb/DOM/Document.h>
+#include <LibWeb/DOM/EventDispatcher.h>
+
+namespace Web::DOM {
+
+AbortSignal::AbortSignal(Document& document)
+    : EventTarget(static_cast<Bindings::ScriptExecutionContext&>(document))
+{
+}
+
+AbortSignal::~AbortSignal()
+{
+}
+
+bool AbortSignal::dispatch_event(NonnullRefPtr<Event> event)
+{
+    return EventDispatcher::dispatch(*this, event);
+}
+
+JS::Object* AbortSignal::create_wrapper(JS::GlobalObject& global_object)
+{
+    return wrap(global_object, *this);
+}
+
+// https://dom.spec.whatwg.org/#abortsignal-add
+void AbortSignal::add_abort_algorithm(Function<void()> abort_algorithm)
+{
+    if (m_aborted)
+        return;
+
+    m_abort_algorithms.append(move(abort_algorithm));
+}
+
+// https://dom.spec.whatwg.org/#abortsignal-signal-abort
+void AbortSignal::signal_abort()
+{
+    if (m_aborted)
+        return;
+
+    m_aborted = true;
+
+    for (auto& algorithm : m_abort_algorithms)
+        algorithm();
+
+    m_abort_algorithms.clear();
+
+    dispatch_event(Event::create(HTML::EventNames::abort));
+}
+
+}

Userland/Libraries/LibWeb/DOM/AbortSignal.h

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+/*
+ * Copyright (c) 2021, Luke Wilde <lukew@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/RefCounted.h>
+#include <AK/Weakable.h>
+#include <LibWeb/Bindings/Wrappable.h>
+#include <LibWeb/DOM/EventTarget.h>
+#include <LibWeb/DOM/Window.h>
+#include <LibWeb/Forward.h>
+
+namespace Web::DOM {
+
+// https://dom.spec.whatwg.org/#abortsignal
+class AbortSignal final
+    : public RefCounted<AbortSignal>
+    , public Weakable<AbortSignal>
+    , public EventTarget
+    , public Bindings::Wrappable {
+public:
+    using WrapperType = Bindings::AbortSignalWrapper;
+
+    using RefCounted::ref;
+    using RefCounted::unref;
+
+    static NonnullRefPtr<AbortSignal> create(Document& document)
+    {
+        return adopt_ref(*new AbortSignal(document));
+    }
+
+    static NonnullRefPtr<AbortSignal> create_with_global_object(Bindings::WindowObject& window_object)
+    {
+        return AbortSignal::create(window_object.impl().document());
+    }
+
+    virtual ~AbortSignal() override;
+
+    void add_abort_algorithm(Function<void()>);
+
+    // https://dom.spec.whatwg.org/#dom-abortsignal-aborted
+    bool aborted() const { return m_aborted; }
+
+    void signal_abort();
+
+    // ^EventTarget
+    virtual void ref_event_target() override { ref(); }
+    virtual void unref_event_target() override { unref(); }
+    virtual bool dispatch_event(NonnullRefPtr<Event>) override;
+    virtual JS::Object* create_wrapper(JS::GlobalObject&) override;
+
+private:
+    AbortSignal(Document& document);
+
+    // https://dom.spec.whatwg.org/#abortsignal-aborted-flag
+    bool m_aborted { false };
+
+    // https://dom.spec.whatwg.org/#abortsignal-abort-algorithms
+    // FIXME: This should be a set.
+    Vector<Function<void()>> m_abort_algorithms;
+};
+
+}

Userland/Libraries/LibWeb/DOM/AbortSignal.idl

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+[Exposed=(Window,Worker)]
+interface AbortSignal : EventTarget {
+    // FIXME: [NewObject] static AbortSignal abort();
+
+    readonly attribute boolean aborted;
+
+    // FIXME: attribute EventHandler onabort;
+};