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

Tag #1287

js/src/builtin/Promise.cpp

@@ -12,10 +12,12 @@
 
 #include "jscntxt.h"
 #include "jsexn.h"
+#include "jsiter.h"
 
 #include "gc/Heap.h"
 #include "js/Debug.h"
 #include "vm/AsyncFunction.h"
+#include "vm/AsyncIteration.h"
 
 #include "jsobjinlines.h"
 
@@ -36,6 +38,16 @@ enum PromiseHandler {
     PromiseHandlerThrower,
     PromiseHandlerAsyncFunctionAwaitFulfilled,
     PromiseHandlerAsyncFunctionAwaitRejected,
+    PromiseHandlerAsyncGeneratorAwaitFulfilled,
+    PromiseHandlerAsyncGeneratorAwaitRejected,
+
+    // Async Iteration proposal 6.1.1.2.1.
+    // Async iterator handlers take the resolved value and create new iterator
+    // objects.  To do so it needs to forward whether the iterator is done. In
+    // spec, this is achieved via the [[Done]] internal slot. We enumerate both
+    // true and false cases here.
+    PromiseHandlerAsyncIteratorValueUnwrapDone,
+    PromiseHandlerAsyncIteratorValueUnwrapNotDone,
 };
 
 enum ResolutionMode {
@@ -178,6 +190,7 @@ enum ReactionRecordSlots {
     ReactionRecordSlot_IncumbentGlobalObject,
     ReactionRecordSlot_Flags,
     ReactionRecordSlot_HandlerArg,
+    ReactionRecordSlot_Generator,
     ReactionRecordSlots,
 };
 
@@ -185,6 +198,7 @@ enum ReactionRecordSlots {
 #define REACTION_FLAG_FULFILLED                 0x2
 #define REACTION_FLAG_IGNORE_DEFAULT_RESOLUTION 0x4
 #define REACTION_FLAG_ASYNC_FUNCTION_AWAIT      0x8
+#define REACTION_FLAG_ASYNC_GENERATOR_AWAIT     0x10
 
 // ES2016, 25.4.1.2.
 class PromiseReactionRecord : public NativeObject
@@ -220,6 +234,22 @@ class PromiseReactionRecord : public NativeObject
         int32_t flags = this->flags();
         return flags & REACTION_FLAG_ASYNC_FUNCTION_AWAIT;
     }
+    void setIsAsyncGeneratorAwait(Handle<AsyncGeneratorObject*> asyncGenObj) {
+        int32_t flags = this->flags();
+        flags |= REACTION_FLAG_ASYNC_GENERATOR_AWAIT;
+        setFixedSlot(ReactionRecordSlot_Flags, Int32Value(flags));
+
+        setFixedSlot(ReactionRecordSlot_Generator, ObjectValue(*asyncGenObj));
+    }
+    bool isAsyncGeneratorAwait() {
+        int32_t flags = this->flags();
+        return flags & REACTION_FLAG_ASYNC_GENERATOR_AWAIT;
+    }
+    AsyncGeneratorObject* asyncGenerator() {
+        MOZ_ASSERT(isAsyncGeneratorAwait());
+        return &getFixedSlot(ReactionRecordSlot_Generator).toObject()
+                                                          .as<AsyncGeneratorObject>();
+    }
     Value handler() {
         MOZ_ASSERT(targetState() != JS::PromiseState::Pending);
         uint32_t slot = targetState() == JS::PromiseState::Fulfilled
@@ -846,6 +876,34 @@ AsyncFunctionAwaitPromiseReactionJob(JSContext* cx, Handle<PromiseReactionRecord
     return true;
 }
 
+static MOZ_MUST_USE bool
+AsyncGeneratorAwaitPromiseReactionJob(JSContext* cx, Handle<PromiseReactionRecord*> reaction,
+                                      MutableHandleValue rval)
+{
+    MOZ_ASSERT(reaction->isAsyncGeneratorAwait());
+
+    RootedValue handlerVal(cx, reaction->handler());
+    RootedValue argument(cx, reaction->handlerArg());
+    Rooted<AsyncGeneratorObject*> asyncGenObj(cx, reaction->asyncGenerator());
+
+    int32_t handlerNum = int32_t(handlerVal.toNumber());
+    MOZ_ASSERT(handlerNum == PromiseHandlerAsyncGeneratorAwaitFulfilled ||
+               handlerNum == PromiseHandlerAsyncGeneratorAwaitRejected);
+
+    // Await's handlers don't return a value, nor throw exception.
+    // They fail only on OOM.
+    if (handlerNum == PromiseHandlerAsyncGeneratorAwaitFulfilled) {
+        if (!AsyncGeneratorAwaitedFulfilled(cx, asyncGenObj, argument))
+            return false;
+    } else {
+        if (!AsyncGeneratorAwaitedRejected(cx, asyncGenObj, argument))
+            return false;
+    }
+
+    rval.setUndefined();
+    return true;
+}
+
 // ES2016, 25.4.2.1.
 /**
  * Callback triggering the fulfill/reject reaction for a resolved Promise,
@@ -891,6 +949,8 @@ PromiseReactionJob(JSContext* cx, unsigned argc, Value* vp)
     Rooted<PromiseReactionRecord*> reaction(cx, &reactionObj->as<PromiseReactionRecord>());
     if (reaction->isAsyncFunctionAwait())
         return AsyncFunctionAwaitPromiseReactionJob(cx, reaction, args.rval());
+    if (reaction->isAsyncGeneratorAwait())
+        return AsyncGeneratorAwaitPromiseReactionJob(cx, reaction, args.rval());
 
     // Step 3.
     RootedValue handlerVal(cx, reaction->handler());
@@ -907,11 +967,21 @@ PromiseReactionJob(JSContext* cx, unsigned argc, Value* vp)
         // Step 4.
         if (handlerNum == PromiseHandlerIdentity) {
             handlerResult = argument;
-        } else {
+        } else if (handlerNum == PromiseHandlerThrower) {
             // Step 5.
-            MOZ_ASSERT(handlerNum == PromiseHandlerThrower);
             resolutionMode = RejectMode;
             handlerResult = argument;
+        } else {
+            MOZ_ASSERT(handlerNum == PromiseHandlerAsyncIteratorValueUnwrapDone ||
+                       handlerNum == PromiseHandlerAsyncIteratorValueUnwrapNotDone);
+
+            bool done = handlerNum == PromiseHandlerAsyncIteratorValueUnwrapDone;
+            // Async Iteration proposal 6.1.1.2.1 step 1.
+            RootedObject resultObj(cx, CreateIterResultObject(cx, argument, done));
+            if (!resultObj)
+                return false;
+
+            handlerResult = ObjectValue(*resultObj);
         }
     } else {
         // Step 6.
@@ -2221,6 +2291,185 @@ js::AsyncFunctionAwait(JSContext* cx, Handle<PromiseObject*> resultPromise, Hand
     return PerformPromiseThenWithReaction(cx, promise, reaction);
 }
 
+// Async Iteration proposal 5.1 steps 2-9.
+MOZ_MUST_USE bool
+js::AsyncGeneratorAwait(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj,
+                        HandleValue value)
+{
+    // Step 2.
+    Rooted<PromiseObject*> promise(cx, CreatePromiseObjectWithoutResolutionFunctions(cx));
+    if (!promise)
+        return false;
+
+    // Steps 3.
+    if (!ResolvePromiseInternal(cx, promise, value))
+        return false;
+
+    // Steps 4-5.
+    RootedValue onFulfilled(cx, Int32Value(PromiseHandlerAsyncGeneratorAwaitFulfilled));
+    RootedValue onRejected(cx, Int32Value(PromiseHandlerAsyncGeneratorAwaitRejected));
+
+    RootedObject incumbentGlobal(cx);
+    if (!GetObjectFromIncumbentGlobal(cx, &incumbentGlobal))
+        return false;
+
+    // Step 6 (skipped).
+
+    // Steps 7-8.
+    Rooted<PromiseReactionRecord*> reaction(cx, NewReactionRecord(cx, nullptr,
+                                                                  onFulfilled, onRejected,
+                                                                  nullptr, nullptr,
+                                                                  incumbentGlobal));
+    if (!reaction)
+        return false;
+
+    reaction->setIsAsyncGeneratorAwait(asyncGenObj);
+
+    // Step 9.
+    return PerformPromiseThenWithReaction(cx, promise, reaction);
+}
+
+// Async Iteration proposal 6.4.3.3.
+MOZ_MUST_USE bool
+js::AsyncGeneratorResolve(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj,
+                          HandleValue value, bool done)
+{
+    // Step 1 (implicit).
+
+    // Steps 2-3.
+    MOZ_ASSERT(!asyncGenObj->isQueueEmpty());
+
+    // Step 4.
+    Rooted<AsyncGeneratorRequest*> request(
+        cx, AsyncGeneratorObject::dequeueRequest(cx, asyncGenObj));
+    if (!request)
+        return false;
+
+    // Step 5.
+    RootedObject resultPromise(cx, request->promise());
+
+    // Step 6.
+    Rooted<PromiseObject*> promise(cx, CreatePromiseObjectWithoutResolutionFunctions(cx));
+    if (!promise)
+        return false;
+
+    // Step 7.
+    if (!ResolvePromiseInternal(cx, promise, value))
+        return false;
+
+    // Steps 8-9.
+    RootedValue onFulfilled(cx, Int32Value(done
+                                           ? PromiseHandlerAsyncIteratorValueUnwrapDone
+                                           : PromiseHandlerAsyncIteratorValueUnwrapNotDone));
+
+    RootedObject incumbentGlobal(cx);
+    if (!GetObjectFromIncumbentGlobal(cx, &incumbentGlobal))
+        return false;
+
+    // Step 10.
+    Rooted<PromiseReactionRecord*> reaction(cx, NewReactionRecord(cx, resultPromise, onFulfilled,
+                                                                  UndefinedHandleValue,
+                                                                  nullptr, nullptr,
+                                                                  incumbentGlobal));
+    if (!reaction)
+        return false;
+
+    if (!PerformPromiseThenWithReaction(cx, promise, reaction))
+        return false;
+
+    // Step 11.
+    if (!AsyncGeneratorResumeNext(cx, asyncGenObj))
+        return false;
+
+    // Step 12.
+    return true;
+}
+
+// Async Iteration proposal 6.4.3.4.
+MOZ_MUST_USE bool
+js::AsyncGeneratorReject(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj,
+                         HandleValue exception)
+{
+    // Step 1 (implicit).
+
+    // Steps 2-3.
+    MOZ_ASSERT(!asyncGenObj->isQueueEmpty());
+
+    // Step 4.
+    Rooted<AsyncGeneratorRequest*> request(
+        cx, AsyncGeneratorObject::dequeueRequest(cx, asyncGenObj));
+    if (!request)
+        return false;
+
+    // Step 5.
+    RootedObject resultPromise(cx, request->promise());
+
+    // Step 6.
+    if (!RejectMaybeWrappedPromise(cx, resultPromise, exception))
+        return false;
+
+    // Step 7.
+    if (!AsyncGeneratorResumeNext(cx, asyncGenObj))
+        return false;
+
+    // Step 8.
+    return true;
+}
+
+// Async Iteration proposal 6.4.3.6.
+MOZ_MUST_USE bool
+js::AsyncGeneratorEnqueue(JSContext* cx, HandleValue asyncGenVal,
+                          CompletionKind completionKind, HandleValue completionValue,
+                          MutableHandleValue result)
+{
+    // Step 1 (implicit).
+
+    // Step 2.
+    RootedObject resultPromise(cx, CreatePromiseObjectWithoutResolutionFunctions(cx));
+    if (!resultPromise)
+        return false;
+
+    // Step 3.
+    if (!asyncGenVal.isObject() || !asyncGenVal.toObject().is<AsyncGeneratorObject>()) {
+        // Step 3.a.
+        RootedValue badGeneratorError(cx);
+        if (!GetTypeError(cx, JSMSG_NOT_AN_ASYNC_GENERATOR, &badGeneratorError))
+            return false;
+
+        // Step 3.b.
+        if (!RejectMaybeWrappedPromise(cx, resultPromise, badGeneratorError))
+            return false;
+
+        // Step 3.c.
+        result.setObject(*resultPromise);
+        return true;
+    }
+
+    Rooted<AsyncGeneratorObject*> asyncGenObj(
+        cx, &asyncGenVal.toObject().as<AsyncGeneratorObject>());
+
+    // Step 5 (reordered).
+    Rooted<AsyncGeneratorRequest*> request(
+        cx, AsyncGeneratorRequest::create(cx, completionKind, completionValue, resultPromise));
+    if (!request)
+        return false;
+
+    // Steps 4, 6.
+    if (!AsyncGeneratorObject::enqueueRequest(cx, asyncGenObj, request))
+        return false;
+
+    // Step 7.
+    if (!asyncGenObj->isExecuting()) {
+        // Step 8.
+        if (!AsyncGeneratorResumeNext(cx, asyncGenObj))
+            return false;
+    }
+
+    // Step 9.
+    result.setObject(*resultPromise);
+    return true;
+}
+
 // ES2016, 25.4.5.3.
 bool
 js::Promise_then(JSContext* cx, unsigned argc, Value* vp)