Create JSPromise

src/js/promise.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function(global, utils, extrasUtils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
 // -------------------------------------------------------------------
 // Imports
 
 var InternalArray = utils.InternalArray;
 var promiseAsyncStackIDSymbol =
     utils.ImportNow("promise_async_stack_id_symbol");
 var promiseHandledBySymbol =
     utils.ImportNow("promise_handled_by_symbol");
 var promiseForwardingHandlerSymbol =
     utils.ImportNow("promise_forwarding_handler_symbol");
 var promiseHasHandlerSymbol =
     utils.ImportNow("promise_has_handler_symbol");
-var promiseRejectReactionsSymbol =
-    utils.ImportNow("promise_reject_reactions_symbol");
-var promiseFulfillReactionsSymbol =
-    utils.ImportNow("promise_fulfill_reactions_symbol");
-var promiseDeferredReactionSymbol =
-    utils.ImportNow("promise_deferred_reaction_symbol");
 var promiseHandledHintSymbol =
     utils.ImportNow("promise_handled_hint_symbol");
 var promiseRawSymbol = utils.ImportNow("promise_raw_symbol");
 var promiseStateSymbol = utils.ImportNow("promise_state_symbol");
 var promiseResultSymbol = utils.ImportNow("promise_result_symbol");
 var SpeciesConstructor;
 var speciesSymbol = utils.ImportNow("species_symbol");
 var toStringTagSymbol = utils.ImportNow("to_string_tag_symbol");
 var ObjectHasOwnProperty;
 var GlobalPromise = global.Promise;
+var PromiseThen = GlobalPromise.prototype.then;
 
 utils.Import(function(from) {
   ObjectHasOwnProperty = from.ObjectHasOwnProperty;
   SpeciesConstructor = from.SpeciesConstructor;
 });
 
 // -------------------------------------------------------------------
 
 // Core functionality.
 
-function PromiseSet(promise, status, value) {
-  SET_PRIVATE(promise, promiseStateSymbol, status);
-  SET_PRIVATE(promise, promiseResultSymbol, value);
-
-  // There are 3 possible states for the resolve, reject symbols when we add
-  // a new callback --
-  // 1) UNDEFINED -- This is the zero state where there is no callback
-  // registered. When we see this state, we directly attach the callbacks to
-  // the symbol.
-  // 2) !IS_ARRAY -- There is a single callback directly attached to the
-  // symbols. We need to create a new array to store additional callbacks.
-  // 3) IS_ARRAY -- There are multiple callbacks already registered,
-  // therefore we can just push the new callback to the existing array.
-  SET_PRIVATE(promise, promiseFulfillReactionsSymbol, UNDEFINED);
-  SET_PRIVATE(promise, promiseRejectReactionsSymbol, UNDEFINED);
-
-  // This symbol is used only when one deferred needs to be attached. When more
-  // than one deferred need to be attached the promise, we attach them directly
-  // to the promiseFulfillReactionsSymbol and promiseRejectReactionsSymbol and
-  // reset this back to UNDEFINED.
-  SET_PRIVATE(promise, promiseDeferredReactionSymbol, UNDEFINED);
-
-  return promise;
-}
-
-function PromiseCreateAndSet(status, value) {
-  var promise = %promise_internal_constructor();
-  // If debug is active, notify about the newly created promise first.
-  if (DEBUG_IS_ACTIVE) PromiseSet(promise, kPending, UNDEFINED);
-  return PromiseSet(promise, status, value);
-}
-
-function PromiseInit(promise) {
-  return PromiseSet(promise, kPending, UNDEFINED);
-}
-
 function PromiseHandle(value, handler, deferred) {
   var debug_is_active = DEBUG_IS_ACTIVE;
   try {
     if (debug_is_active) %DebugPushPromise(deferred.promise);
     var result = handler(value);
     if (IS_UNDEFINED(deferred.resolve)) {
       ResolvePromise(deferred.promise, result);
     } else {
       %_Call(deferred.resolve, UNDEFINED, result);
     }
   } %catch (exception) {  // Natives syntax to mark this catch block.
     try {
       if (IS_UNDEFINED(deferred.reject)) {
         // Pass false for debugEvent so .then chaining or throwaway promises
         // in async functions do not trigger redundant ExceptionEvents.
         %PromiseReject(deferred.promise, exception, false);
-        PromiseSet(deferred.promise, kRejected, exception);
       } else {
         %_Call(deferred.reject, UNDEFINED, exception);
       }
     } catch (e) { }
   } finally {
     if (debug_is_active) %DebugPopPromise();
   }
 }
 
 function PromiseDebugGetInfo(deferreds, status) {
@@ skipping 15 matching lines @@
       name = "async function";
     } else {
       id = %DebugNextMicrotaskId();
       name = status === kFulfilled ? "Promise.resolve" : "Promise.reject";
       %DebugAsyncTaskEvent("enqueue", id, name);
     }
   }
   return [id, name];
 }
 
-function PromiseAttachCallbacks(promise, deferred, onResolve, onReject) {
-  var maybeResolveCallbacks =
-      GET_PRIVATE(promise, promiseFulfillReactionsSymbol);
-  if (IS_UNDEFINED(maybeResolveCallbacks)) {
-    SET_PRIVATE(promise, promiseFulfillReactionsSymbol, onResolve);
-    SET_PRIVATE(promise, promiseRejectReactionsSymbol, onReject);
-    SET_PRIVATE(promise, promiseDeferredReactionSymbol, deferred);
-  } else if (!IS_ARRAY(maybeResolveCallbacks)) {
-    var resolveCallbacks = new InternalArray();
-    var rejectCallbacks = new InternalArray();
-    var existingDeferred = GET_PRIVATE(promise, promiseDeferredReactionSymbol);
-
-    resolveCallbacks.push(
-        maybeResolveCallbacks, existingDeferred, onResolve, deferred);
-    rejectCallbacks.push(GET_PRIVATE(promise, promiseRejectReactionsSymbol),
-                         existingDeferred,
-                         onReject,
-                         deferred);
-
-    SET_PRIVATE(promise, promiseFulfillReactionsSymbol, resolveCallbacks);
-    SET_PRIVATE(promise, promiseRejectReactionsSymbol, rejectCallbacks);
-    SET_PRIVATE(promise, promiseDeferredReactionSymbol, UNDEFINED);
-  } else {
-    maybeResolveCallbacks.push(onResolve, deferred);
-    GET_PRIVATE(promise, promiseRejectReactionsSymbol).push(onReject, deferred);
-  }
-}
-
 function PromiseIdResolveHandler(x) { return x; }
 function PromiseIdRejectHandler(r) { %_ReThrow(r); }
 SET_PRIVATE(PromiseIdRejectHandler, promiseForwardingHandlerSymbol, true);
 
 // -------------------------------------------------------------------
 // Define exported functions.
 
 // For bootstrapper.
 
+// This is used by utils and v8-extras.
 function PromiseCreate() {
-  return PromiseInit(%promise_internal_constructor());
+  return %promise_internal_constructor();
 }
 
 // ES#sec-promise-resolve-functions
 // Promise Resolve Functions, steps 6-13
 function ResolvePromise(promise, resolution) {
   if (resolution === promise) {
     var exception = %make_type_error(kPromiseCyclic, resolution);
     %PromiseReject(promise, exception, true);
-    PromiseSet(promise, kRejected, exception);
     return;
   }
   if (IS_RECEIVER(resolution)) {
     // 25.4.1.3.2 steps 8-12
     try {
       var then = resolution.then;
     } catch (e) {
       %PromiseReject(promise, e, true);
-      PromiseSet(promise, kRejected, e);
       return;
     }
 
     // Resolution is a native promise and if it's already resolved or
     // rejected, shortcircuit the resolution procedure by directly
     // reusing the value from the promise.
     if (%is_promise(resolution) && then === PromiseThen) {
-      var thenableState = GET_PRIVATE(resolution, promiseStateSymbol);
+      var thenableState = %PromiseStatus(resolution);
       if (thenableState === kFulfilled) {
         // This goes inside the if-else to save one symbol lookup in
         // the slow path.
-        var thenableValue = GET_PRIVATE(resolution, promiseResultSymbol);
-        %PromiseFulfill(promise, kFulfilled, thenableValue,
-                       promiseFulfillReactionsSymbol);
-        PromiseSet(promise, kFulfilled, thenableValue);
+        var thenableValue = %PromiseResult(resolution);
+        %PromiseFulfill(promise, kFulfilled, thenableValue);
         SET_PRIVATE(promise, promiseHasHandlerSymbol, true);
         return;
       } else if (thenableState === kRejected) {
-        var thenableValue = GET_PRIVATE(resolution, promiseResultSymbol);
+        var thenableValue = %PromiseResult(resolution);
         if (!HAS_DEFINED_PRIVATE(resolution, promiseHasHandlerSymbol)) {
           // Promise has already been rejected, but had no handler.
           // Revoke previously triggered reject event.
           %PromiseRevokeReject(resolution);
         }
         // Don't cause a debug event as this case is forwarding a rejection
         %PromiseReject(promise, thenableValue, false);
-        PromiseSet(promise, kRejected, thenableValue);
         SET_PRIVATE(resolution, promiseHasHandlerSymbol, true);
         return;
       }
     }
 
     if (IS_CALLABLE(then)) {
       if (DEBUG_IS_ACTIVE && %is_promise(resolution)) {
           // Mark the dependency of the new promise on the resolution
         SET_PRIVATE(resolution, promiseHandledBySymbol, promise);
       }
       %EnqueuePromiseResolveThenableJob(promise, resolution, then);
       return;
     }
   }
-  %PromiseFulfill(promise, kFulfilled, resolution,
-                  promiseFulfillReactionsSymbol);
-  PromiseSet(promise, kFulfilled, resolution);
+  %PromiseFulfill(promise, kFulfilled, resolution);
 }
 
 // Only used by async-await.js
 function RejectPromise(promise, reason, debugEvent) {
   %PromiseReject(promise, reason, debugEvent);
-  PromiseSet(promise, kRejected, reason);
 }
 
 // Export to bindings
 function DoRejectPromise(promise, reason) {
   %PromiseReject(promise, reason, true);
-  PromiseSet(promise, kRejected, reason);
 }
 
 // The resultCapability.promise is only ever fulfilled internally,
 // so we don't need the closures to protect against accidentally
 // calling them multiple times.
 function CreateInternalPromiseCapability() {
   return {
-    promise: PromiseCreate(),
+    promise: %promise_internal_constructor(),
     resolve: UNDEFINED,
     reject: UNDEFINED
   };
 }
 
 // ES#sec-newpromisecapability
 // NewPromiseCapability ( C )
 function NewPromiseCapability(C, debugEvent) {
   if (C === GlobalPromise) {
     // Optimized case, avoid extra closure.
-    var promise = PromiseCreate();
+    var promise = %promise_internal_constructor();
     // TODO(gsathya): Remove container for callbacks when this is
     // moved to CPP/TF.
     var callbacks = %create_resolving_functions(promise, debugEvent);
     return {
       promise: promise,
       resolve: callbacks[kResolveCallback],
       reject: callbacks[kRejectCallback]
     };
   }
 
@@ skipping 12 matching lines @@
 }
 
 // ES#sec-promise.reject
 // Promise.reject ( x )
 function PromiseReject(r) {
   if (!IS_RECEIVER(this)) {
     throw %make_type_error(kCalledOnNonObject, PromiseResolve);
   }
   if (this === GlobalPromise) {
     // Optimized case, avoid extra closure.
-    var promise = PromiseCreateAndSet(kRejected, r);
+    var promise = %promise_create_and_set(kRejected, r);
     // Trigger debug events if the debugger is on, as Promise.reject is
     // equivalent to throwing an exception directly.
     %PromiseRejectEventFromStack(promise, r);
     return promise;
   } else {
     var promiseCapability = NewPromiseCapability(this, true);
     %_Call(promiseCapability.reject, UNDEFINED, r);
     return promiseCapability.promise;
   }
 }
 
-function PerformPromiseThen(promise, onResolve, onReject, resultCapability) {
-  if (!IS_CALLABLE(onResolve)) onResolve = PromiseIdResolveHandler;
-  if (!IS_CALLABLE(onReject)) onReject = PromiseIdRejectHandler;
-
-  var status = GET_PRIVATE(promise, promiseStateSymbol);
-  switch (status) {
-    case kPending:
-      PromiseAttachCallbacks(promise, resultCapability, onResolve, onReject);
-      break;
-    case kFulfilled:
-      %EnqueuePromiseReactionJob(GET_PRIVATE(promise, promiseResultSymbol),
-                                 onResolve, resultCapability, kFulfilled);
-      break;
-    case kRejected:
-      if (!HAS_DEFINED_PRIVATE(promise, promiseHasHandlerSymbol)) {
-        // Promise has already been rejected, but had no handler.
-        // Revoke previously triggered reject event.
-        %PromiseRevokeReject(promise);
-      }
-      %EnqueuePromiseReactionJob(GET_PRIVATE(promise, promiseResultSymbol),
-                                 onReject, resultCapability, kRejected);
-      break;
-  }
-
-  // Mark this promise as having handler.
-  SET_PRIVATE(promise, promiseHasHandlerSymbol, true);
-  return resultCapability.promise;
-}
-
-// ES#sec-promise.prototype.then
-// Promise.prototype.then ( onFulfilled, onRejected )
-// Multi-unwrapped chaining with thenable coercion.
-function PromiseThen(onResolve, onReject) {
-  if (!%is_promise(this)) {
-    throw %make_type_error(kNotAPromise, this);
-  }
-
-  var constructor = SpeciesConstructor(this, GlobalPromise);
-  var resultCapability;
-  if (constructor === GlobalPromise) {
-    resultCapability = CreateInternalPromiseCapability();
-  } else {
-    // Pass false for debugEvent so .then chaining does not trigger
-    // redundant ExceptionEvents.
-    resultCapability = NewPromiseCapability(constructor, false);
-  }
-  return PerformPromiseThen(this, onResolve, onReject, resultCapability);
-}
-
 // ES#sec-promise.prototype.catch
 // Promise.prototype.catch ( onRejected )
 function PromiseCatch(onReject) {
   return this.then(UNDEFINED, onReject);
 }
 
 // Combinators.
 
 // ES#sec-promise.resolve
 // Promise.resolve ( x )
 function PromiseResolve(x) {
   if (!IS_RECEIVER(this)) {
     throw %make_type_error(kCalledOnNonObject, PromiseResolve);
   }
   if (%is_promise(x) && x.constructor === this) return x;
 
   // Avoid creating resolving functions.
   if (this === GlobalPromise) {
-    var promise = PromiseCreate();
+    var promise = %promise_internal_constructor();
     ResolvePromise(promise, x);
     return promise;
   }
 
   // debugEvent is not so meaningful here as it will be resolved
   var promiseCapability = NewPromiseCapability(this, true);
   %_Call(promiseCapability.resolve, UNDEFINED, x);
   return promiseCapability.promise;
 }
 
@@ skipping 122 matching lines @@
   // with another Promise, or an intermediate, hidden, throwaway Promise
   // within async/await), then recurse on the outer Promise.
   // In this case, the dependency is one possible way that the Promise
   // could be resolved, so it does not subsume the other following cases.
   var outerPromise = GET_PRIVATE(promise, promiseHandledBySymbol);
   if (outerPromise &&
       PromiseHasUserDefinedRejectHandlerRecursive(outerPromise)) {
     return true;
   }
 
-  var queue = GET_PRIVATE(promise, promiseRejectReactionsSymbol);
-  var deferred = GET_PRIVATE(promise, promiseDeferredReactionSymbol);
+  if (!%is_promise(promise)) return false;
+
+  var queue = %PromiseRejectReactions(promise);
+  var deferred = %PromiseDeferred(promise);
 
   if (IS_UNDEFINED(queue)) return false;
 
   if (!IS_ARRAY(queue)) {
     return PromiseHasUserDefinedRejectHandlerCheck(queue, deferred);
   }
 
-  for (var i = 0; i < queue.length; i += 2) {
-    if (PromiseHasUserDefinedRejectHandlerCheck(queue[i], queue[i + 1])) {
+  for (var i = 0; i < queue.length; i++) {
+    if (PromiseHasUserDefinedRejectHandlerCheck(queue[i], deferred[i])) {
       return true;
     }
   }
   return false;
 }
 
 // Return whether the promise will be handled by a user-defined reject
 // handler somewhere down the promise chain. For this, we do a depth-first
 // search for a reject handler that's not the default PromiseIdRejectHandler.
 // This function also traverses dependencies of one Promise on another,
@@ skipping 17 matching lines @@
 utils.InstallFunctions(GlobalPromise, DONT_ENUM, [
   "reject", PromiseReject,
   "all", PromiseAll,
   "race", PromiseRace,
   "resolve", PromiseResolve
 ]);
 
 utils.InstallGetter(GlobalPromise, speciesSymbol, PromiseSpecies);
 
 utils.InstallFunctions(GlobalPromise.prototype, DONT_ENUM, [
-  "then", PromiseThen,
   "catch", PromiseCatch
 ]);
 
 %InstallToContext([
   "promise_catch", PromiseCatch,
   "promise_create", PromiseCreate,
   "promise_has_user_defined_reject_handler", PromiseHasUserDefinedRejectHandler,
   "promise_reject", DoRejectPromise,
   // TODO(gsathya): Remove this once we update the promise builtin.
   "promise_internal_reject", RejectPromise,
   "promise_resolve", ResolvePromise,
   "promise_then", PromiseThen,
   "promise_handle", PromiseHandle,
-  "promise_debug_get_info", PromiseDebugGetInfo
+  "promise_debug_get_info", PromiseDebugGetInfo,
+  "new_promise_capability", NewPromiseCapability,
+  "internal_promise_capability", CreateInternalPromiseCapability,
+  "promise_id_resolve_handler", PromiseIdResolveHandler,
+  "promise_id_reject_handler", PromiseIdRejectHandler
 ]);
 
 // This allows extras to create promises quickly without building extra
 // resolve/reject closures, and allows them to later resolve and reject any
 // promise without having to hold on to those closures forever.
 utils.InstallFunctions(extrasUtils, 0, [
   "createPromise", PromiseCreate,
   "resolvePromise", ResolvePromise,
   "rejectPromise", DoRejectPromise,
   "markPromiseAsHandled", MarkPromiseAsHandled
 ]);
 
 utils.Export(function(to) {
   to.PromiseCreate = PromiseCreate;
   to.PromiseThen = PromiseThen;
 
   to.CreateInternalPromiseCapability = CreateInternalPromiseCapability;
-  to.PerformPromiseThen = PerformPromiseThen;
   to.ResolvePromise = ResolvePromise;
   to.RejectPromise = RejectPromise;
 });
 
 })