Bug 1331092 - Part 7: Implement Async Generator yield*.

Tag #1287

js/src/builtin/Promise.cpp

@@ -2329,6 +2329,165 @@ js::AsyncGeneratorAwait(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj
     return PerformPromiseThenWithReaction(cx, promise, reaction);
 }
 
+// Async Iteration proposal 6.1.3.2.1 %AsyncFromSyncIteratorPrototype%.next
+// Async Iteration proposal 6.1.3.2.2 %AsyncFromSyncIteratorPrototype%.return
+// Async Iteration proposal 6.1.3.2.3 %AsyncFromSyncIteratorPrototype%.throw
+bool
+js::AsyncFromSyncIteratorMethod(JSContext* cx, CallArgs& args, CompletionKind completionKind)
+{
+    // Step 1.
+    RootedValue thisVal(cx, args.thisv());
+
+    // Step 2.
+    RootedObject resultPromise(cx, CreatePromiseObjectWithoutResolutionFunctions(cx));
+    if (!resultPromise)
+        return false;
+
+    // Step 3.
+    if (!thisVal.isObject() || !thisVal.toObject().is<AsyncFromSyncIteratorObject>()) {
+        // Step 3.a.
+        RootedValue badGeneratorError(cx);
+        if (!GetTypeError(cx, JSMSG_NOT_AN_ASYNC_ITERATOR, &badGeneratorError))
+            return false;
+
+        // Step 3.b.
+        if (!RejectMaybeWrappedPromise(cx, resultPromise, badGeneratorError))
+            return false;
+
+        // Step 3.c.
+        args.rval().setObject(*resultPromise);
+        return true;
+    }
+
+    Rooted<AsyncFromSyncIteratorObject*> asyncIter(
+        cx, &thisVal.toObject().as<AsyncFromSyncIteratorObject>());
+
+    // Step 4.
+    RootedObject iter(cx, asyncIter->iterator());
+
+    RootedValue resultVal(cx);
+    RootedValue func(cx);
+    if (completionKind == CompletionKind::Normal) {
+        // 6.1.3.2.1 steps 5-6 (partially).
+        if (!GetProperty(cx, iter, iter, cx->names().next, &func))
+            return AbruptRejectPromise(cx, args, resultPromise, nullptr);
+    } else if (completionKind == CompletionKind::Return) {
+        // 6.1.3.2.2 steps 5-6.
+        if (!GetProperty(cx, iter, iter, cx->names().return_, &func))
+            return AbruptRejectPromise(cx, args, resultPromise, nullptr);
+
+        // Step 7.
+        if (func.isNullOrUndefined()) {
+            // Step 7.a.
+            RootedObject resultObj(cx, CreateIterResultObject(cx, args.get(0), true));
+            if (!resultObj)
+                return AbruptRejectPromise(cx, args, resultPromise, nullptr);
+
+            RootedValue resultVal(cx, ObjectValue(*resultObj));
+
+            // Step 7.b.
+            if (!ResolvePromiseInternal(cx, resultPromise, resultVal))
+                return AbruptRejectPromise(cx, args, resultPromise, nullptr);
+
+            // Step 7.c.
+            args.rval().setObject(*resultPromise);
+            return true;
+        }
+    } else {
+        // 6.1.3.2.3 steps 5-6.
+        MOZ_ASSERT(completionKind == CompletionKind::Throw);
+        if (!GetProperty(cx, iter, iter, cx->names().throw_, &func))
+            return AbruptRejectPromise(cx, args, resultPromise, nullptr);
+
+        // Step 7.
+        if (func.isNullOrUndefined()) {
+            // Step 7.a.
+            if (!RejectMaybeWrappedPromise(cx, resultPromise, args.get(0)))
+                return AbruptRejectPromise(cx, args, resultPromise, nullptr);
+
+            // Step 7.b.
+            args.rval().setObject(*resultPromise);
+            return true;
+        }
+    }
+
+    // 6.1.3.2.1 steps 5-6 (partially).
+    // 6.1.3.2.2, 6.1.3.2.3 steps 8-9.
+    RootedValue iterVal(cx, ObjectValue(*iter));
+    FixedInvokeArgs<1> args2(cx);
+    args2[0].set(args.get(0));
+    if (!js::Call(cx, func, iterVal, args2, &resultVal))
+        return AbruptRejectPromise(cx, args, resultPromise, nullptr);
+
+    // 6.1.3.2.1 steps 5-6 (partially).
+    // 6.1.3.2.2, 6.1.3.2.3 steps 10.
+    if (!resultVal.isObject()) {
+        CheckIsObjectKind kind;
+        switch (completionKind) {
+          case CompletionKind::Normal:
+            kind = CheckIsObjectKind::IteratorNext;
+            break;
+          case CompletionKind::Throw:
+            kind = CheckIsObjectKind::IteratorThrow;
+            break;
+          case CompletionKind::Return:
+            kind = CheckIsObjectKind::IteratorReturn;
+            break;
+        }
+        MOZ_ALWAYS_FALSE(ThrowCheckIsObject(cx, kind));
+        return AbruptRejectPromise(cx, args, resultPromise, nullptr);
+    }
+
+    RootedObject resultObj(cx, &resultVal.toObject());
+
+    // Following step numbers are for 6.1.3.2.1.
+    // For 6.1.3.2.2 and 6.1.3.2.3, steps 7-16 corresponds to steps 11-20.
+
+    // Steps 7-8.
+    RootedValue value(cx);
+    if (!GetProperty(cx, resultObj, resultObj, cx->names().value, &value))
+        return AbruptRejectPromise(cx, args, resultPromise, nullptr);
+
+    // Steps 9-10.
+    RootedValue doneVal(cx);
+    if (!GetProperty(cx, resultObj, resultObj, cx->names().done, &doneVal))
+        return AbruptRejectPromise(cx, args, resultPromise, nullptr);
+    bool done = ToBoolean(doneVal);
+
+    // Step 11.
+    Rooted<PromiseObject*> promise(cx, CreatePromiseObjectWithoutResolutionFunctions(cx));
+    if (!promise)
+        return false;
+
+    // Step 12.
+    if (!ResolvePromiseInternal(cx, promise, value))
+        return false;
+
+    // Steps 13-14.
+    RootedValue onFulfilled(cx, Int32Value(done
+                                           ? PromiseHandlerAsyncIteratorValueUnwrapDone
+                                           : PromiseHandlerAsyncIteratorValueUnwrapNotDone));
+
+    RootedObject incumbentGlobal(cx);
+    if (!GetObjectFromIncumbentGlobal(cx, &incumbentGlobal))
+        return false;
+
+    // Step 15.
+    Rooted<PromiseReactionRecord*> reaction(cx, NewReactionRecord(cx, resultPromise, onFulfilled,
+                                                                  UndefinedHandleValue,
+                                                                  nullptr, nullptr,
+                                                                  incumbentGlobal));
+    if (!reaction)
+        return false;
+
+    if (!PerformPromiseThenWithReaction(cx, promise, reaction))
+        return false;
+
+    // Step 16.
+    args.rval().setObject(*resultPromise);
+    return true;
+}
+
 // Async Iteration proposal 6.4.3.3.
 MOZ_MUST_USE bool
 js::AsyncGeneratorResolve(JSContext* cx, Handle<AsyncGeneratorObject*> asyncGenObj,