Bug 1331092 - Part 2: Implement Async Generator except yield*.

Tag #1287

js/src/vm/AsyncIteration.cpp

@@ -0,0 +1,564 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "vm/AsyncIteration.h"
+
+#include "jsarray.h"
+#include "jscompartment.h"
+
+#include "builtin/Promise.h"
+#include "vm/GeneratorObject.h"
+#include "vm/GlobalObject.h"
+#include "vm/Interpreter.h"
+#include "vm/SelfHosting.h"
+
+#include "jscntxtinlines.h"
+#include "jsobjinlines.h"
+
+#include "vm/NativeObject-inl.h"
+
+using namespace js;
+using namespace js::gc;
+
+#define UNWRAPPED_ASYNC_WRAPPED_SLOT 1
+#define WRAPPED_ASYNC_UNWRAPPED_SLOT 0
+
+// Async Iteration proposal 2.3.10 Runtime Semantics: EvaluateBody.
+static bool
+WrappedAsyncGenerator(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    RootedFunction wrapped(cx, &args.callee().as<JSFunction>());
+    RootedValue unwrappedVal(cx, wrapped->getExtendedSlot(WRAPPED_ASYNC_UNWRAPPED_SLOT));
+    RootedFunction unwrapped(cx, &unwrappedVal.toObject().as<JSFunction>());
+    RootedValue thisValue(cx, args.thisv());
+
+    // Step 1.
+    RootedValue generatorVal(cx);
+    InvokeArgs args2(cx);
+    if (!args2.init(cx, argc))
+        return false;
+    for (size_t i = 0, len = argc; i < len; i++)
+        args2[i].set(args[i]);
+    if (!Call(cx, unwrappedVal, thisValue, args2, &generatorVal))
+        return false;
+
+    // Step 2.
+    Rooted<AsyncGeneratorObject*> asyncGenObj(
+        cx, AsyncGeneratorObject::create(cx, wrapped, generatorVal));
+    if (!asyncGenObj)
+        return false;
+
+    // Step 3 (skipped).
+    // Done in AsyncGeneratorObject::create and generator.
+
+    // Step 4.
+    args.rval().setObject(*asyncGenObj);
+    return true;
+}
+
+JSObject*
+js::WrapAsyncGeneratorWithProto(JSContext* cx, HandleFunction unwrapped, HandleObject proto)
+{
+    MOZ_ASSERT(unwrapped->isAsync());
+    MOZ_ASSERT(proto, "We need an explicit prototype to avoid the default"
+                      "%FunctionPrototype% fallback in NewFunctionWithProto().");
+
+    // Create a new function with AsyncGeneratorPrototype, reusing the name and
+    // the length of `unwrapped`.
+
+    RootedAtom funName(cx, unwrapped->explicitName());
+    uint16_t length;
+    if (!JSFunction::getLength(cx, unwrapped, &length))
+        return nullptr;
+
+    RootedFunction wrapped(cx, NewFunctionWithProto(cx, WrappedAsyncGenerator, length,
+                                                    JSFunction::NATIVE_FUN, nullptr,
+                                                    funName, proto,
+                                                    AllocKind::FUNCTION_EXTENDED,
+                                                    TenuredObject));
+    if (!wrapped)
+        return nullptr;
+
+    if (unwrapped->hasCompileTimeName())
+        wrapped->setCompileTimeName(unwrapped->compileTimeName());
+
+    // Link them to each other to make GetWrappedAsyncGenerator and
+    // GetUnwrappedAsyncGenerator work.
+    unwrapped->setExtendedSlot(UNWRAPPED_ASYNC_WRAPPED_SLOT, ObjectValue(*wrapped));
+    wrapped->setExtendedSlot(WRAPPED_ASYNC_UNWRAPPED_SLOT, ObjectValue(*unwrapped));
+
+    return wrapped;
+}
+
+JSObject*
+js::WrapAsyncGenerator(JSContext* cx, HandleFunction unwrapped)
+{
+    RootedObject proto(cx, GlobalObject::getOrCreateAsyncGenerator(cx, cx->global()));
+    if (!proto)
+        return nullptr;
+
+    return WrapAsyncGeneratorWithProto(cx, unwrapped, proto);
+}
+
+bool
+js::IsWrappedAsyncGenerator(JSFunction* fun)
+{
+    return fun->maybeNative() == WrappedAsyncGenerator;
+}
+
+JSFunction*
+js::GetWrappedAsyncGenerator(JSFunction* unwrapped)
+{
+    MOZ_ASSERT(unwrapped->isAsync());
+    return &unwrapped->getExtendedSlot(UNWRAPPED_ASYNC_WRAPPED_SLOT).toObject().as<JSFunction>();
+}
+
+JSFunction*
+js::GetUnwrappedAsyncGenerator(JSFunction* wrapped)
+{
+    MOZ_ASSERT(IsWrappedAsyncGenerator(wrapped));
+    JSFunction* unwrapped = &wrapped->getExtendedSlot(WRAPPED_ASYNC_UNWRAPPED_SLOT)
+                            .toObject().as<JSFunction>();
+    MOZ_ASSERT(unwrapped->isAsync());
+    return unwrapped;
+}
+
+static MOZ_MUST_USE bool
+AsyncGeneratorResume(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj,
+                     CompletionKind completionKind, HandleValue argument);
+
+// Async Iteration proposal 5.1.1 Await Fulfilled Functions.
+MOZ_MUST_USE bool
+js::AsyncGeneratorAwaitedFulfilled(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj,
+                                   HandleValue value)
+{
+    return AsyncGeneratorResume(cx, asyncGenObj, CompletionKind::Normal, value);
+}
+
+// Async Iteration proposal 5.1.2 Await Rejected Functions.
+MOZ_MUST_USE bool
+js::AsyncGeneratorAwaitedRejected(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj,
+                                  HandleValue reason)
+{
+    return AsyncGeneratorResume(cx, asyncGenObj, CompletionKind::Throw, reason);
+}
+
+// Async Iteration proposal 6.4.1.2 AsyncGenerator.prototype.next.
+static bool
+AsyncGeneratorNext(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    // Steps 1-3.
+    return AsyncGeneratorEnqueue(cx, args.thisv(), CompletionKind::Normal, args.get(0),
+                                 args.rval());
+}
+
+// Async Iteration proposal 6.4.1.3 AsyncGenerator.prototype.return.
+static bool
+AsyncGeneratorReturn(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    // Steps 1-3.
+    return AsyncGeneratorEnqueue(cx, args.thisv(), CompletionKind::Return, args.get(0),
+                                 args.rval());
+}
+
+// Async Iteration proposal 6.4.1.4 AsyncGenerator.prototype.throw.
+static bool
+AsyncGeneratorThrow(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    // Steps 1-3.
+    return AsyncGeneratorEnqueue(cx, args.thisv(), CompletionKind::Throw, args.get(0),
+                                 args.rval());
+}
+
+const Class AsyncGeneratorObject::class_ = {
+    "AsyncGenerator",
+    JSCLASS_HAS_RESERVED_SLOTS(AsyncGeneratorObject::Slots)
+};
+
+// ES 2017 draft 9.1.13.
+template <typename ProtoGetter>
+static JSObject*
+OrdinaryCreateFromConstructor(JSContext* cx, HandleFunction fun,
+                              ProtoGetter protoGetter, const Class* clasp)
+{
+    // Step 1 (skipped).
+
+    // Step 2.
+    RootedValue protoVal(cx);
+    if (!GetProperty(cx, fun, fun, cx->names().prototype, &protoVal))
+        return nullptr;
+
+    RootedObject proto(cx, protoVal.isObject() ? &protoVal.toObject() : nullptr);
+    if (!proto) {
+        proto = protoGetter(cx, cx->global());
+        if (!proto)
+            return nullptr;
+    }
+
+    // Step 3.
+    return NewNativeObjectWithGivenProto(cx, clasp, proto);
+}
+
+/* static */ AsyncGeneratorObject*
+AsyncGeneratorObject::create(JSContext* cx, HandleFunction asyncGen, HandleValue generatorVal)
+{
+    MOZ_ASSERT(generatorVal.isObject());
+    MOZ_ASSERT(generatorVal.toObject().is<GeneratorObject>());
+
+    RootedObject obj(
+        cx, OrdinaryCreateFromConstructor(cx, asyncGen,
+                                          GlobalObject::getOrCreateAsyncGeneratorPrototype,
+                                          &class_));
+    if (!obj)
+        return nullptr;
+
+    Handle<AsyncGeneratorObject*> asyncGenObj = obj.as<AsyncGeneratorObject>();
+
+    // Async Iteration proposal 6.4.3.2 AsyncGeneratorStart.
+    // Step 6.
+    asyncGenObj->setGenerator(generatorVal);
+
+    // Step 7.
+    asyncGenObj->setSuspendedStart();
+
+    // Step 8.
+    asyncGenObj->clearSingleQueueRequest();
+
+    return asyncGenObj;
+}
+
+/* static */ MOZ_MUST_USE bool
+AsyncGeneratorObject::enqueueRequest(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj,
+                                     Handle<AsyncGeneratorRequest*> request)
+{
+    if (asyncGenObj->isSingleQueue()) {
+        if (asyncGenObj->isSingleQueueEmpty()) {
+            asyncGenObj->setSingleQueueRequest(request);
+            return true;
+        }
+
+        RootedArrayObject queue(cx, NewDenseEmptyArray(cx));
+        if (!queue)
+            return false;
+
+        if (!NewbornArrayPush(cx, queue, ObjectValue(*asyncGenObj->singleQueueRequest())))
+            return false;
+        if (!NewbornArrayPush(cx, queue, ObjectValue(*request)))
+            return false;
+
+        asyncGenObj->setQueue(queue);
+        return true;
+    }
+
+    RootedArrayObject queue(cx, asyncGenObj->queue());
+
+    FixedInvokeArgs<1> args(cx);
+    args[0].setObject(*request);
+    args.setThis(ObjectValue(*queue));
+    return CallJSNative(cx, array_push, args);
+}
+
+/* static */ AsyncGeneratorRequest*
+AsyncGeneratorObject::dequeueRequest(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj)
+{
+    if (asyncGenObj->isSingleQueue()) {
+        AsyncGeneratorRequest* request = asyncGenObj->singleQueueRequest();
+        asyncGenObj->clearSingleQueueRequest();
+        return request;
+    }
+
+    RootedArrayObject queue(cx, asyncGenObj->queue());
+
+    FixedInvokeArgs<0> args(cx);
+    args.setThis(ObjectValue(*queue));
+    if (!CallJSNative(cx, array_shift, args))
+        return nullptr;
+
+    return &args.rval().toObject().as<AsyncGeneratorRequest>();
+}
+
+/* static */ AsyncGeneratorRequest*
+AsyncGeneratorObject::peekRequest(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj)
+{
+    if (asyncGenObj->isSingleQueue())
+        return asyncGenObj->singleQueueRequest();
+
+    RootedArrayObject queue(cx, asyncGenObj->queue());
+
+    RootedValue requestVal(cx);
+    if (!GetElement(cx, queue, queue, 0, &requestVal))
+        return nullptr;
+
+    return &requestVal.toObject().as<AsyncGeneratorRequest>();
+}
+
+const Class AsyncGeneratorRequest::class_ = {
+    "AsyncGeneratorRequest",
+    JSCLASS_HAS_RESERVED_SLOTS(AsyncGeneratorRequest::Slots)
+};
+
+// Async Iteration proposal 6.4.3.1.
+/* static */ AsyncGeneratorRequest*
+AsyncGeneratorRequest::create(JSContext* cx, CompletionKind completionKind_,
+                              HandleValue completionValue_, HandleObject promise_)
+{
+    RootedObject obj(cx, NewNativeObjectWithGivenProto(cx, &class_, nullptr));
+    if (!obj)
+        return nullptr;
+
+    Handle<AsyncGeneratorRequest*> request = obj.as<AsyncGeneratorRequest>();
+    request->setCompletionKind(completionKind_);
+    request->setCompletionValue(completionValue_);
+    request->setPromise(promise_);
+    return request;
+}
+
+// Async Iteration proposal 6.4.3.2 steps 5.d-g.
+static MOZ_MUST_USE bool
+AsyncGeneratorReturned(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj,
+                       HandleValue value)
+{
+    // Step 5.d.
+    asyncGenObj->setCompleted();
+
+    // Step 5.e (done in bytecode).
+    // Step 5.f.i (implicit).
+
+    // Step 5.g.
+    return AsyncGeneratorResolve(cx, asyncGenObj, value, true);
+}
+
+// Async Iteration proposal 6.4.3.2 steps 5.d, f.
+static MOZ_MUST_USE bool
+AsyncGeneratorThrown(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj)
+{
+    // Step 5.d.
+    asyncGenObj->setCompleted();
+
+    // Not much we can do about uncatchable exceptions, so just bail.
+    if (!cx->isExceptionPending())
+        return false;
+
+    // Step 5.f.i.
+    RootedValue value(cx);
+    if (!GetAndClearException(cx, &value))
+        return false;
+
+    // Step 5.f.ii.
+    return AsyncGeneratorReject(cx, asyncGenObj, value);
+}
+
+// Async Iteration proposal 6.4.3.5.
+MOZ_MUST_USE bool
+js::AsyncGeneratorResumeNext(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj)
+{
+    // Step 1 (implicit).
+
+    // Steps 2-3.
+    MOZ_ASSERT(!asyncGenObj->isExecuting());
+
+    // Steps 4-5.
+    if (asyncGenObj->isQueueEmpty())
+        return true;
+
+    // Steps 6-7.
+    Rooted<AsyncGeneratorRequest*> request(
+        cx, AsyncGeneratorObject::peekRequest(cx, asyncGenObj));
+    if (!request)
+        return false;
+
+    // Step 8.
+    CompletionKind completionKind = request->completionKind();
+
+    // Step 9.
+    if (completionKind != CompletionKind::Normal) {
+        // Step 9.a.
+        if (asyncGenObj->isSuspendedStart())
+            asyncGenObj->setCompleted();
+
+        // Step 9.b.
+        if (asyncGenObj->isCompleted()) {
+            // Step 9.b.i.
+            RootedValue value(cx, request->completionValue());
+            if (completionKind == CompletionKind::Return)
+                return AsyncGeneratorResolve(cx, asyncGenObj, value, true);
+            // Step 9.b.ii.
+            return AsyncGeneratorReject(cx, asyncGenObj, value);
+        }
+    } else if (asyncGenObj->isCompleted()) {
+        // Step 10.
+        return AsyncGeneratorResolve(cx, asyncGenObj, UndefinedHandleValue, true);
+    }
+
+    // Step 11.
+    MOZ_ASSERT(asyncGenObj->isSuspendedStart() || asyncGenObj->isSuspendedYield());
+
+    // Step 15 (reordered).
+    asyncGenObj->setExecuting();
+
+    RootedValue argument(cx, request->completionValue());
+
+    // Steps 12-14, 16-20.
+    return AsyncGeneratorResume(cx, asyncGenObj, completionKind, argument);
+}
+
+// Async Iteration proposal 6.2.1.2 (partially).
+// Most steps are done in generator.
+static MOZ_MUST_USE bool
+AsyncGeneratorYield(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj,
+                    HandleValue value, bool done)
+{
+    // Step 6.
+    asyncGenObj->setSuspendedYield();
+
+    // Step 10.c.
+    return AsyncGeneratorResolve(cx, asyncGenObj, value, done);
+}
+
+// Async Iteration proposal 6.4.3.5 steps 12-14, 16-20.
+// Async Iteration proposal 6.2.1.2 step 10.
+// Async Iteration proposal 6.4.3.2 step 5.f-g.
+// Async Iteration proposal 5.1 steps 2-9.
+// Execution context switching is handled in generator.
+static MOZ_MUST_USE bool
+AsyncGeneratorResume(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj,
+                     CompletionKind completionKind, HandleValue argument)
+{
+    RootedValue generatorVal(cx, asyncGenObj->generatorVal());
+
+    // 6.4.3.5 steps 12-14, 16-20.
+    HandlePropertyName funName = completionKind == CompletionKind::Normal
+                                 ? cx->names().StarGeneratorNext
+                                 : completionKind == CompletionKind::Throw
+                                 ? cx->names().StarGeneratorThrow
+                                 : cx->names().StarGeneratorReturn;
+    FixedInvokeArgs<1> args(cx);
+    args[0].set(argument);
+    RootedValue result(cx);
+    if (!CallSelfHostedFunction(cx, funName, generatorVal, args, &result)) {
+        // 6.4.3.2 step 5.d, f.
+        return AsyncGeneratorThrown(cx, asyncGenObj);
+    }
+
+    // The following code corresponds to the following 3 cases:
+    //   * yield
+    //   * await
+    //   * return
+    // For await and return, property access is done on an internal result
+    // object and it's not observable.
+    // For yield, it's done on an user-provided result object, and it's
+    // observable, so perform in that order in all cases.
+
+    RootedObject resultObj(cx, &result.toObject());
+    RootedValue value(cx);
+    RootedValue doneVal(cx);
+
+    // 6.2.1.2 step 10.a.
+    if (!GetProperty(cx, resultObj, resultObj, cx->names().value, &value))
+        return false;
+
+    // 6.2.1.2 step 10.b.
+    if (!GetProperty(cx, resultObj, resultObj, cx->names().done, &doneVal))
+        return false;
+
+    // 6.2.1.2 step 10.c.
+    if (asyncGenObj->generatorObj()->isAfterYield())
+        return AsyncGeneratorYield(cx, asyncGenObj, value, ToBoolean(doneVal));
+
+    // 6.4.3.2 step 5.d-g.
+    if (ToBoolean(doneVal)) {
+        MOZ_ASSERT(!asyncGenObj->generatorObj()->isAfterAwait());
+        return AsyncGeneratorReturned(cx, asyncGenObj, value);
+    }
+
+    MOZ_ASSERT(asyncGenObj->generatorObj()->isAfterAwait());
+
+    // 5.1 steps 2-9.
+    return AsyncGeneratorAwait(cx, asyncGenObj, value);
+}
+
+static const JSFunctionSpec async_iterator_proto_methods[] = {
+    JS_SELF_HOSTED_SYM_FN(asyncIterator, "AsyncIteratorIdentity", 0, 0),
+    JS_FS_END
+};
+
+static const JSFunctionSpec async_generator_methods[] = {
+    JS_FN("next", AsyncGeneratorNext, 1, 0),
+    JS_FN("throw", AsyncGeneratorThrow, 1, 0),
+    JS_FN("return", AsyncGeneratorReturn, 1, 0),
+    JS_FS_END
+};
+
+/* static */ MOZ_MUST_USE bool
+GlobalObject::initAsyncGenerators(JSContext* cx, Handle<GlobalObject*> global)
+{
+    if (global->getReservedSlot(ASYNC_ITERATOR_PROTO).isObject())
+        return true;
+
+    // Async Iteration proposal 6.1.2 %AsyncIteratorPrototype%.
+    RootedObject asyncIterProto(cx, GlobalObject::createBlankPrototype<PlainObject>(cx, global));
+    if (!asyncIterProto)
+        return false;
+    if (!DefinePropertiesAndFunctions(cx, asyncIterProto, nullptr, async_iterator_proto_methods))
+        return false;
+
+    // Async Iteration proposal 6.4.1 %AsyncGeneratorPrototype%.
+    RootedObject asyncGenProto(
+        cx, GlobalObject::createBlankPrototypeInheriting(cx, global, &PlainObject::class_,
+                                                         asyncIterProto));
+    if (!asyncGenProto)
+        return false;
+    if (!DefinePropertiesAndFunctions(cx, asyncGenProto, nullptr, async_generator_methods) ||
+        !DefineToStringTag(cx, asyncGenProto, cx->names().AsyncGenerator))
+    {
+        return false;
+    }
+
+    // Async Iteration proposal 6.3.3 %AsyncGenerator%.
+    RootedObject asyncGenerator(cx, NewSingletonObjectWithFunctionPrototype(cx, global));
+    if (!asyncGenerator)
+        return false;
+    if (!JSObject::setDelegate(cx, asyncGenerator))
+        return false;
+    if (!LinkConstructorAndPrototype(cx, asyncGenerator, asyncGenProto, JSPROP_READONLY,
+                                     JSPROP_READONLY) ||
+        !DefineToStringTag(cx, asyncGenerator, cx->names().AsyncGeneratorFunction))
+    {
+        return false;
+    }
+
+    RootedValue function(cx, global->getConstructor(JSProto_Function));
+    if (!function.toObjectOrNull())
+        return false;
+    RootedObject proto(cx, &function.toObject());
+    RootedAtom name(cx, cx->names().AsyncGeneratorFunction);
+
+    // Async Iteration proposal 6.3.2 %AsyncGeneratorFunction%.
+    RootedObject asyncGenFunction(
+        cx, NewFunctionWithProto(cx, AsyncGeneratorConstructor, 1, JSFunction::NATIVE_CTOR,
+                                 nullptr, name, proto, gc::AllocKind::FUNCTION, SingletonObject));
+    if (!asyncGenFunction)
+        return false;
+    if (!LinkConstructorAndPrototype(cx, asyncGenFunction, asyncGenerator,
+                                     JSPROP_PERMANENT | JSPROP_READONLY, JSPROP_READONLY))
+    {
+        return false;
+    }
+
+    global->setReservedSlot(ASYNC_ITERATOR_PROTO, ObjectValue(*asyncIterProto));
+    global->setReservedSlot(ASYNC_GENERATOR, ObjectValue(*asyncGenerator));
+    global->setReservedSlot(ASYNC_GENERATOR_FUNCTION, ObjectValue(*asyncGenFunction));
+    global->setReservedSlot(ASYNC_GENERATOR_PROTO, ObjectValue(*asyncGenProto));
+    return true;
+}