LibWeb: Implement most WebIDL promise operations

4 files changed, 209 insertions, 0 deletions

diff --git a/Userland/Libraries/LibJS/Runtime/Promise.h b/Userland/Libraries/LibJS/Runtime/Promise.h
index a4ef47c143..82692393dc 100644
--- a/Userland/Libraries/LibJS/Runtime/Promise.h
+++ b/Userland/Libraries/LibJS/Runtime/Promise.h
@@ -45,6 +45,7 @@ public:
     Value perform_then(Value on_fulfilled, Value on_rejected, Optional<PromiseCapability> result_capability);
 
     bool is_handled() const { return m_is_handled; }
+    void set_is_handled() { m_is_handled = true; }
 
 protected:
     explicit Promise(Object& prototype);
diff --git a/Userland/Libraries/LibWeb/CMakeLists.txt b/Userland/Libraries/LibWeb/CMakeLists.txt
index be29c7b82a..bd46f8b1e3 100644
--- a/Userland/Libraries/LibWeb/CMakeLists.txt
+++ b/Userland/Libraries/LibWeb/CMakeLists.txt
@@ -415,6 +415,7 @@ set(SOURCES
     WebIDL/CallbackType.cpp
     WebIDL/DOMException.cpp
     WebIDL/OverloadResolution.cpp
+    WebIDL/Promise.cpp
     WebSockets/WebSocket.cpp
     XHR/EventNames.cpp
     XHR/ProgressEvent.cpp
diff --git a/Userland/Libraries/LibWeb/WebIDL/Promise.cpp b/Userland/Libraries/LibWeb/WebIDL/Promise.cpp
new file mode 100644
index 0000000000..17b42d8c0a
--- /dev/null
+++ b/Userland/Libraries/LibWeb/WebIDL/Promise.cpp
@@ -0,0 +1,178 @@
+/*
+ * Copyright (c) 2022, Linus Groh <linusg@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Function.h>
+#include <LibJS/Runtime/PromiseConstructor.h>
+#include <LibJS/Runtime/Realm.h>
+#include <LibWeb/Bindings/ExceptionOrUtils.h>
+#include <LibWeb/WebIDL/ExceptionOr.h>
+#include <LibWeb/WebIDL/Promise.h>
+
+namespace Web::WebIDL {
+
+// https://webidl.spec.whatwg.org/#a-new-promise
+JS::PromiseCapability create_promise(JS::Realm& realm)
+{
+    auto& vm = realm.vm();
+
+    // 1. Let constructor be realm.[[Intrinsics]].[[%Promise%]].
+    auto* constructor = realm.intrinsics().promise_constructor();
+
+    // Return ? NewPromiseCapability(constructor).
+    // NOTE: When called with %Promise%, NewPromiseCapability can't throw.
+    return MUST(JS::new_promise_capability(vm, constructor));
+}
+
+// https://webidl.spec.whatwg.org/#a-promise-resolved-with
+JS::PromiseCapability create_resolved_promise(JS::Realm& realm, JS::Value value)
+{
+    auto& vm = realm.vm();
+
+    // 1. Let value be the result of converting x to an ECMAScript value.
+
+    // 2. Let constructor be realm.[[Intrinsics]].[[%Promise%]].
+    auto* constructor = realm.intrinsics().promise_constructor();
+
+    // 3. Let promiseCapability be ? NewPromiseCapability(constructor).
+    // NOTE: When called with %Promise%, NewPromiseCapability can't throw.
+    auto promise_capability = MUST(JS::new_promise_capability(vm, constructor));
+
+    // 4. Perform ! Call(promiseCapability.[[Resolve]], undefined, « value »).
+    MUST(JS::call(vm, promise_capability.resolve, JS::js_undefined(), value));
+
+    // 5. Return promiseCapability.
+    return promise_capability;
+}
+
+// https://webidl.spec.whatwg.org/#a-promise-rejected-with
+JS::PromiseCapability create_rejected_promise(JS::Realm& realm, JS::Value reason)
+{
+    auto& vm = realm.vm();
+
+    // 1. Let constructor be realm.[[Intrinsics]].[[%Promise%]].
+    auto* constructor = realm.intrinsics().promise_constructor();
+
+    // 2. Let promiseCapability be ? NewPromiseCapability(constructor).
+    // NOTE: When called with %Promise%, NewPromiseCapability can't throw.
+    auto promise_capability = MUST(JS::new_promise_capability(vm, constructor));
+
+    // 3. Perform ! Call(promiseCapability.[[Reject]], undefined, « r »).
+    MUST(JS::call(vm, promise_capability.reject, JS::js_undefined(), reason));
+
+    // 4. Return promiseCapability.
+    return promise_capability;
+}
+
+// https://webidl.spec.whatwg.org/#resolve
+void resolve_promise(JS::VM& vm, JS::PromiseCapability const& promise_capability, JS::Value value)
+{
+    // 1. If x is not given, then let it be the undefined value.
+    // NOTE: This is done via the default argument.
+
+    // 2. Let value be the result of converting x to an ECMAScript value.
+
+    // 3. Perform ! Call(p.[[Resolve]], undefined, « value »).
+    MUST(JS::call(vm, promise_capability.resolve, JS::js_undefined(), value));
+}
+
+// https://webidl.spec.whatwg.org/#reject
+void reject_promise(JS::VM& vm, JS::PromiseCapability const& promise_capability, JS::Value reason)
+{
+    // 1. Perform ! Call(p.[[Reject]], undefined, « r »).
+    MUST(JS::call(vm, promise_capability.reject, JS::js_undefined(), reason));
+}
+
+// https://webidl.spec.whatwg.org/#dfn-perform-steps-once-promise-is-settled
+JS::NonnullGCPtr<JS::Promise> react_to_promise(JS::PromiseCapability const& promise_capability, Optional<ReactionSteps> on_fulfilled_callback, Optional<ReactionSteps> on_rejected_callback)
+{
+    auto& realm = promise_capability.promise->shape().realm();
+    auto& vm = realm.vm();
+
+    // 1. Let onFulfilledSteps be the following steps given argument V:
+    auto on_fulfilled_steps = [on_fulfilled_callback = move(on_fulfilled_callback)](JS::VM& vm) -> JS::ThrowCompletionOr<JS::Value> {
+        // 1. Let value be the result of converting V to an IDL value of type T.
+        auto value = vm.argument(0);
+
+        // 2. If there is a set of steps to be run if the promise was fulfilled, then let result be the result of performing them, given value if T is not undefined. Otherwise, let result be value.
+        auto result = on_fulfilled_callback.has_value()
+            ? TRY(Bindings::throw_dom_exception_if_needed(vm, [&] { return (*on_fulfilled_callback)(value); }))
+            : value;
+
+        // 3. Return result, converted to an ECMAScript value.
+        return result;
+    };
+
+    // 2. Let onFulfilled be CreateBuiltinFunction(onFulfilledSteps, « »):
+    auto* on_fulfilled = JS::NativeFunction::create(realm, move(on_fulfilled_steps), 1, "");
+
+    // 3. Let onRejectedSteps be the following steps given argument R:
+    auto on_rejected_steps = [&realm, on_rejected_callback = move(on_rejected_callback)](JS::VM& vm) -> JS::ThrowCompletionOr<JS::Value> {
+        // 1. Let reason be the result of converting R to an IDL value of type any.
+        auto reason = vm.argument(0);
+
+        // 2. If there is a set of steps to be run if the promise was rejected, then let result be the result of performing them, given reason. Otherwise, let result be a promise rejected with reason.
+        auto result = on_rejected_callback.has_value()
+            ? TRY(Bindings::throw_dom_exception_if_needed(vm, [&] { return (*on_rejected_callback)(reason); }))
+            : WebIDL::create_rejected_promise(realm, reason).promise;
+
+        // 3. Return result, converted to an ECMAScript value.
+        return result;
+    };
+
+    // 4. Let onRejected be CreateBuiltinFunction(onRejectedSteps, « »):
+    auto* on_rejected = JS::NativeFunction::create(realm, move(on_rejected_steps), 1, "");
+
+    // 5. Let constructor be promise.[[Promise]].[[Realm]].[[Intrinsics]].[[%Promise%]].
+    auto* constructor = realm.intrinsics().promise_constructor();
+
+    // 6. Let newCapability be ? NewPromiseCapability(constructor).
+    // NOTE: When called with %Promise%, NewPromiseCapability can't throw.
+    auto new_capability = MUST(JS::new_promise_capability(vm, constructor));
+
+    // 7. Return PerformPromiseThen(promise.[[Promise]], onFulfilled, onRejected, newCapability).
+    auto* promise = static_cast<JS::Promise*>(promise_capability.promise);
+    auto value = promise->perform_then(on_fulfilled, on_rejected, new_capability);
+    return verify_cast<JS::Promise>(value.as_object());
+}
+
+// https://webidl.spec.whatwg.org/#upon-fulfillment
+JS::NonnullGCPtr<JS::Promise> upon_fulfillment(JS::PromiseCapability const& promise_capability, ReactionSteps steps)
+{
+    // 1. Return the result of reacting to promise:
+    return react_to_promise(promise_capability,
+        // - If promise was fulfilled with value v, then:
+        [steps = move(steps)](auto value) {
+            // 1. Perform steps with v.
+            // NOTE: The `return` is not immediately obvious, but `steps` may be something like
+            // "Return the result of ...", which we also need to do _here_.
+            return steps(value);
+        },
+        {});
+}
+
+// https://webidl.spec.whatwg.org/#upon-rejection
+JS::NonnullGCPtr<JS::Promise> upon_rejection(JS::PromiseCapability const& promise_capability, ReactionSteps steps)
+{
+    // 1. Return the result of reacting to promise:
+    return react_to_promise(promise_capability, {},
+        // - If promise was rejected with reason r, then:
+        [steps = move(steps)](auto reason) {
+            // 1. Perform steps with r.
+            // NOTE: The `return` is not immediately obvious, but `steps` may be something like
+            // "Return the result of ...", which we also need to do _here_.
+            return steps(reason);
+        });
+}
+
+// https://webidl.spec.whatwg.org/#mark-a-promise-as-handled
+void mark_promise_as_handled(JS::PromiseCapability const& promise_capability)
+{
+    // To mark as handled a Promise<T> promise, set promise.[[Promise]].[[PromiseIsHandled]] to true.
+    auto* promise = static_cast<JS::Promise*>(promise_capability.promise);
+    promise->set_is_handled();
+}
+
+}
diff --git a/Userland/Libraries/LibWeb/WebIDL/Promise.h b/Userland/Libraries/LibWeb/WebIDL/Promise.h
new file mode 100644
index 0000000000..65122b59df
--- /dev/null
+++ b/Userland/Libraries/LibWeb/WebIDL/Promise.h
@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2022, Linus Groh <linusg@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <LibJS/Forward.h>
+#include <LibJS/Runtime/PromiseReaction.h>
+#include <LibJS/Runtime/Value.h>
+#include <LibJS/SafeFunction.h>
+#include <LibWeb/Forward.h>
+
+namespace Web::WebIDL {
+
+using ReactionSteps = JS::SafeFunction<WebIDL::ExceptionOr<JS::Value>(JS::Value)>;
+
+JS::PromiseCapability create_promise(JS::Realm&);
+JS::PromiseCapability create_resolved_promise(JS::Realm&, JS::Value);
+JS::PromiseCapability create_rejected_promise(JS::Realm&, JS::Value);
+void resolve_promise(JS::VM&, JS::PromiseCapability const&, JS::Value = JS::js_undefined());
+void reject_promise(JS::VM&, JS::PromiseCapability const&, JS::Value);
+JS::NonnullGCPtr<JS::Promise> react_to_promise(JS::PromiseCapability const&, Optional<ReactionSteps> on_fulfilled_callback, Optional<ReactionSteps> on_rejected_callback);
+JS::NonnullGCPtr<JS::Promise> upon_fulfillment(JS::PromiseCapability const&, ReactionSteps);
+JS::NonnullGCPtr<JS::Promise> upon_rejection(JS::PromiseCapability const&, ReactionSteps);
+void mark_promise_as_handled(JS::PromiseCapability const&);
+
+}