// 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 promiseHasHandlerSymbol = utils.ImportNow("promise_has_handler_symbol"); var promiseOnRejectSymbol = utils.ImportNow("promise_on_reject_symbol"); var promiseOnResolveSymbol = utils.ImportNow("promise_on_resolve_symbol"); var promiseRawSymbol = utils.ImportNow("promise_raw_symbol"); var promiseStatusSymbol = utils.ImportNow("promise_status_symbol"); var promiseValueSymbol = utils.ImportNow("promise_value_symbol"); var toStringTagSymbol = utils.ImportNow("to_string_tag_symbol"); // ------------------------------------------------------------------- // Status values: 0 = pending, +1 = resolved, -1 = rejected var lastMicrotaskId = 0; var GlobalPromise = function Promise(resolver) { if (resolver === promiseRawSymbol) return; if (!%_IsConstructCall()) throw MakeTypeError(kNotAPromise, this); if (!IS_CALLABLE(resolver)) throw MakeTypeError(kResolverNotAFunction, resolver); var promise = PromiseInit(this); try { %DebugPushPromise(promise, Promise); resolver(function(x) { PromiseResolve(promise, x) }, function(r) { PromiseReject(promise, r) }); } catch (e) { PromiseReject(promise, e); } finally { %DebugPopPromise(); } } // Core functionality. function PromiseSet(promise, status, value, onResolve, onReject) { SET_PRIVATE(promise, promiseStatusSymbol, status); SET_PRIVATE(promise, promiseValueSymbol, value); SET_PRIVATE(promise, promiseOnResolveSymbol, onResolve); SET_PRIVATE(promise, promiseOnRejectSymbol, onReject); if (DEBUG_IS_ACTIVE) { %DebugPromiseEvent({ promise: promise, status: status, value: value }); } return promise; } function PromiseCreateAndSet(status, value) { var promise = new GlobalPromise(promiseRawSymbol); // If debug is active, notify about the newly created promise first. if (DEBUG_IS_ACTIVE) PromiseSet(promise, 0, UNDEFINED); return PromiseSet(promise, status, value); } function PromiseInit(promise) { return PromiseSet( promise, 0, UNDEFINED, new InternalArray, new InternalArray) } function PromiseDone(promise, status, value, promiseQueue) { if (GET_PRIVATE(promise, promiseStatusSymbol) === 0) { var tasks = GET_PRIVATE(promise, promiseQueue); if (tasks.length) PromiseEnqueue(value, tasks, status); PromiseSet(promise, status, value); } } function PromiseCoerce(constructor, x) { if (!IsPromise(x) && IS_SPEC_OBJECT(x)) { var then; try { then = x.then; } catch(r) { return %_CallFunction(constructor, r, PromiseRejected); } if (IS_CALLABLE(then)) { var deferred = %_CallFunction(constructor, PromiseDeferred); try { %_Call(then, x, deferred.resolve, deferred.reject); } catch(r) { deferred.reject(r); } return deferred.promise; } } return x; } function PromiseHandle(value, handler, deferred) { try { %DebugPushPromise(deferred.promise, PromiseHandle); DEBUG_PREPARE_STEP_IN_IF_STEPPING(handler); var result = handler(value); if (result === deferred.promise) throw MakeTypeError(kPromiseCyclic, result); else if (IsPromise(result)) %_CallFunction(result, deferred.resolve, deferred.reject, PromiseChain); else deferred.resolve(result); } catch (exception) { try { deferred.reject(exception); } catch (e) { } } finally { %DebugPopPromise(); } } function PromiseEnqueue(value, tasks, status) { var id, name, instrumenting = DEBUG_IS_ACTIVE; %EnqueueMicrotask(function() { if (instrumenting) { %DebugAsyncTaskEvent({ type: "willHandle", id: id, name: name }); } for (var i = 0; i < tasks.length; i += 2) { PromiseHandle(value, tasks[i], tasks[i + 1]) } if (instrumenting) { %DebugAsyncTaskEvent({ type: "didHandle", id: id, name: name }); } }); if (instrumenting) { id = ++lastMicrotaskId; name = status > 0 ? "Promise.resolve" : "Promise.reject"; %DebugAsyncTaskEvent({ type: "enqueue", id: id, name: name }); } } function PromiseIdResolveHandler(x) { return x } function PromiseIdRejectHandler(r) { throw r } function PromiseNopResolver() {} // ------------------------------------------------------------------- // Define exported functions. // For bootstrapper. function IsPromise(x) { return IS_SPEC_OBJECT(x) && HAS_DEFINED_PRIVATE(x, promiseStatusSymbol); } function PromiseCreate() { return new GlobalPromise(PromiseNopResolver) } function PromiseResolve(promise, x) { PromiseDone(promise, +1, x, promiseOnResolveSymbol) } function PromiseReject(promise, r) { // Check promise status to confirm that this reject has an effect. // Call runtime for callbacks to the debugger or for unhandled reject. if (GET_PRIVATE(promise, promiseStatusSymbol) == 0) { var debug_is_active = DEBUG_IS_ACTIVE; if (debug_is_active || !HAS_DEFINED_PRIVATE(promise, promiseHasHandlerSymbol)) { %PromiseRejectEvent(promise, r, debug_is_active); } } PromiseDone(promise, -1, r, promiseOnRejectSymbol) } // Convenience. function PromiseDeferred() { if (this === GlobalPromise) { // Optimized case, avoid extra closure. var promise = PromiseInit(new GlobalPromise(promiseRawSymbol)); return { promise: promise, resolve: function(x) { PromiseResolve(promise, x) }, reject: function(r) { PromiseReject(promise, r) } }; } else { var result = {promise: UNDEFINED, reject: UNDEFINED, resolve: UNDEFINED}; result.promise = new this(function(resolve, reject) { result.resolve = resolve; result.reject = reject; }); return result; } } function PromiseResolved(x) { if (this === GlobalPromise) { // Optimized case, avoid extra closure. return PromiseCreateAndSet(+1, x); } else { return new this(function(resolve, reject) { resolve(x) }); } } function PromiseRejected(r) { var promise; if (this === GlobalPromise) { // Optimized case, avoid extra closure. promise = PromiseCreateAndSet(-1, r); // The debug event for this would always be an uncaught promise reject, // which is usually simply noise. Do not trigger that debug event. %PromiseRejectEvent(promise, r, false); } else { promise = new this(function(resolve, reject) { reject(r) }); } return promise; } // Simple chaining. function PromiseChain(onResolve, onReject) { // a.k.a. flatMap onResolve = IS_UNDEFINED(onResolve) ? PromiseIdResolveHandler : onResolve; onReject = IS_UNDEFINED(onReject) ? PromiseIdRejectHandler : onReject; var deferred = %_CallFunction(this.constructor, PromiseDeferred); switch (GET_PRIVATE(this, promiseStatusSymbol)) { case UNDEFINED: throw MakeTypeError(kNotAPromise, this); case 0: // Pending GET_PRIVATE(this, promiseOnResolveSymbol).push(onResolve, deferred); GET_PRIVATE(this, promiseOnRejectSymbol).push(onReject, deferred); break; case +1: // Resolved PromiseEnqueue(GET_PRIVATE(this, promiseValueSymbol), [onResolve, deferred], +1); break; case -1: // Rejected if (!HAS_DEFINED_PRIVATE(this, promiseHasHandlerSymbol)) { // Promise has already been rejected, but had no handler. // Revoke previously triggered reject event. %PromiseRevokeReject(this); } PromiseEnqueue(GET_PRIVATE(this, promiseValueSymbol), [onReject, deferred], -1); break; } // Mark this promise as having handler. SET_PRIVATE(this, promiseHasHandlerSymbol, true); if (DEBUG_IS_ACTIVE) { %DebugPromiseEvent({ promise: deferred.promise, parentPromise: this }); } return deferred.promise; } function PromiseCatch(onReject) { return this.then(UNDEFINED, onReject); } // Multi-unwrapped chaining with thenable coercion. function PromiseThen(onResolve, onReject) { onResolve = IS_CALLABLE(onResolve) ? onResolve : PromiseIdResolveHandler; onReject = IS_CALLABLE(onReject) ? onReject : PromiseIdRejectHandler; var that = this; var constructor = this.constructor; return %_CallFunction( this, function(x) { x = PromiseCoerce(constructor, x); if (x === that) { DEBUG_PREPARE_STEP_IN_IF_STEPPING(onReject); return onReject(MakeTypeError(kPromiseCyclic, x)); } else if (IsPromise(x)) { return x.then(onResolve, onReject); } else { DEBUG_PREPARE_STEP_IN_IF_STEPPING(onResolve); return onResolve(x); } }, onReject, PromiseChain ); } // Combinators. function PromiseCast(x) { // TODO(rossberg): cannot do better until we support @@create. return IsPromise(x) ? x : new this(function(resolve) { resolve(x) }); } function PromiseAll(iterable) { var deferred = %_CallFunction(this, PromiseDeferred); var resolutions = []; try { var count = 0; var i = 0; for (var value of iterable) { this.resolve(value).then( // Nested scope to get closure over current i. // TODO(arv): Use an inner let binding once available. (function(i) { return function(x) { resolutions[i] = x; if (--count === 0) deferred.resolve(resolutions); } })(i), function(r) { deferred.reject(r); }); ++i; ++count; } if (count === 0) { deferred.resolve(resolutions); } } catch (e) { deferred.reject(e) } return deferred.promise; } function PromiseRace(iterable) { var deferred = %_CallFunction(this, PromiseDeferred); try { for (var value of iterable) { this.resolve(value).then( function(x) { deferred.resolve(x) }, function(r) { deferred.reject(r) }); } } catch (e) { deferred.reject(e) } return deferred.promise; } // Utility for debugger function PromiseHasUserDefinedRejectHandlerRecursive(promise) { var queue = GET_PRIVATE(promise, promiseOnRejectSymbol); if (IS_UNDEFINED(queue)) return false; for (var i = 0; i < queue.length; i += 2) { if (queue[i] != PromiseIdRejectHandler) return true; if (PromiseHasUserDefinedRejectHandlerRecursive(queue[i + 1].promise)) { 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. function PromiseHasUserDefinedRejectHandler() { return PromiseHasUserDefinedRejectHandlerRecursive(this); }; // ------------------------------------------------------------------- // Install exported functions. %AddNamedProperty(global, 'Promise', GlobalPromise, DONT_ENUM); %AddNamedProperty(GlobalPromise.prototype, toStringTagSymbol, "Promise", DONT_ENUM | READ_ONLY); utils.InstallFunctions(GlobalPromise, DONT_ENUM, [ "defer", PromiseDeferred, "accept", PromiseResolved, "reject", PromiseRejected, "all", PromiseAll, "race", PromiseRace, "resolve", PromiseCast ]); utils.InstallFunctions(GlobalPromise.prototype, DONT_ENUM, [ "chain", PromiseChain, "then", PromiseThen, "catch", PromiseCatch ]); %InstallToContext([ "promise_catch", PromiseCatch, "promise_chain", PromiseChain, "promise_create", PromiseCreate, "promise_has_user_defined_reject_handler", PromiseHasUserDefinedRejectHandler, "promise_reject", PromiseReject, "promise_resolve", PromiseResolve, "promise_then", PromiseThen, ]); // 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", PromiseResolve, "rejectPromise", PromiseReject ]); })