// Copyright 2013 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
goog.provide('goog.Promise');
goog.require('goog.Thenable');
goog.require('goog.asserts');
goog.require('goog.async.FreeList');
goog.require('goog.async.run');
goog.require('goog.async.throwException');
goog.require('goog.debug.Error');
goog.require('goog.promise.Resolver');
/**
* Promises provide a result that may be resolved asynchronously. A Promise may
* be resolved by being fulfilled with a fulfillment value, rejected with a
* rejection reason, or blocked by another Promise. A Promise is said to be
* settled if it is either fulfilled or rejected. Once settled, the Promise
* result is immutable.
*
* Promises may represent results of any type, including undefined. Rejection
* reasons are typically Errors, but may also be of any type. Closure Promises
* allow for optional type annotations that enforce that fulfillment values are
* of the appropriate types at compile time.
*
* The result of a Promise is accessible by calling {@code then} and registering
* {@code onFulfilled} and {@code onRejected} callbacks. Once the Promise
* is settled, the relevant callbacks are invoked with the fulfillment value or
* rejection reason as argument. Callbacks are always invoked in the order they
* were registered, even when additional {@code then} calls are made from inside
* another callback. A callback is always run asynchronously sometime after the
* scope containing the registering {@code then} invocation has returned.
*
* If a Promise is resolved with another Promise, the first Promise will block
* until the second is settled, and then assumes the same result as the second
* Promise. This allows Promises to depend on the results of other Promises,
* linking together multiple asynchronous operations.
*
* This implementation is compatible with the Promises/A+ specification and
* passes that specification's conformance test suite. A Closure Promise may be
* resolved with a Promise instance (or sufficiently compatible Promise-like
* object) created by other Promise implementations. From the specification,
* Promise-like objects are known as "Thenables".
*
* @see http://promisesaplus.com/
*
* @param {function(
* this:RESOLVER_CONTEXT,
* function((TYPE|IThenable<TYPE>|Thenable)=),
* function(*=)): void} resolver
* Initialization function that is invoked immediately with {@code resolve}
* and {@code reject} functions as arguments. The Promise is resolved or
* rejected with the first argument passed to either function.
* @param {RESOLVER_CONTEXT=} opt_context An optional context for executing the
* resolver function. If unspecified, the resolver function will be executed
* in the default scope.
* @constructor
* @struct
* @final
* @implements {goog.Thenable<TYPE>}
* @template TYPE,RESOLVER_CONTEXT
*/
goog.Promise = function(resolver, opt_context) {
/**
* The internal state of this Promise. Either PENDING, FULFILLED, REJECTED, or
* BLOCKED.
* @private {goog.Promise.State_}
*/
this.state_ = goog.Promise.State_.PENDING;
/**
* The settled result of the Promise. Immutable once set with either a
* fulfillment value or rejection reason.
* @private {*}
*/
this.result_ = undefined;
/**
* For Promises created by calling {@code then()}, the originating parent.
* @private {goog.Promise}
*/
this.parent_ = null;
/**
* The linked list of {@code onFulfilled} and {@code onRejected} callbacks
* added to this Promise by calls to {@code then()}.
* @private {?goog.Promise.CallbackEntry_}
*/
this.callbackEntries_ = null;
/**
* The tail of the linked list of {@code onFulfilled} and {@code onRejected}
* callbacks added to this Promise by calls to {@code then()}.
* @private {?goog.Promise.CallbackEntry_}
*/
this.callbackEntriesTail_ = null;
/**
* Whether the Promise is in the queue of Promises to execute.
* @private {boolean}
*/
this.executing_ = false;
if (goog.Promise.UNHANDLED_REJECTION_DELAY > 0) {
/**
* A timeout ID used when the {@code UNHANDLED_REJECTION_DELAY} is greater
* than 0 milliseconds. The ID is set when the Promise is rejected, and
* cleared only if an {@code onRejected} callback is invoked for the
* Promise (or one of its descendants) before the delay is exceeded.
*
* If the rejection is not handled before the timeout completes, the
* rejection reason is passed to the unhandled rejection handler.
* @private {number}
*/
this.unhandledRejectionId_ = 0;
} else if (goog.Promise.UNHANDLED_REJECTION_DELAY == 0) {
/**
* When the {@code UNHANDLED_REJECTION_DELAY} is set to 0 milliseconds, a
* boolean that is set if the Promise is rejected, and reset to false if an
* {@code onRejected} callback is invoked for the Promise (or one of its
* descendants). If the rejection is not handled before the next timestep,
* the rejection reason is passed to the unhandled rejection handler.
* @private {boolean}
*/
this.hadUnhandledRejection_ = false;
}
if (goog.Promise.LONG_STACK_TRACES) {
/**
* A list of stack trace frames pointing to the locations where this Promise
* was created or had callbacks added to it. Saved to add additional context
* to stack traces when an exception is thrown.
* @private {!Array<string>}
*/
this.stack_ = [];
this.addStackTrace_(new Error('created'));
/**
* Index of the most recently executed stack frame entry.
* @private {number}
*/
this.currentStep_ = 0;
}
// As an optimization, we can skip this if resolver is goog.nullFunction.
// This value is passed internally when creating a promise which will be
// resolved through a more optimized path.
if (resolver != goog.nullFunction) {
try {
var self = this;
resolver.call(
opt_context,
function(value) {
self.resolve_(goog.Promise.State_.FULFILLED, value);
},
function(reason) {
if (goog.DEBUG &&
!(reason instanceof goog.Promise.CancellationError)) {
try {
// Promise was rejected. Step up one call frame to see why.
if (reason instanceof Error) {
throw reason;
} else {
throw new Error('Promise rejected.');
}
} catch (e) {
// Only thrown so browser dev tools can catch rejections of
// promises when the option to break on caught exceptions is
// activated.
}
}
self.resolve_(goog.Promise.State_.REJECTED, reason);
});
} catch (e) {
this.resolve_(goog.Promise.State_.REJECTED, e);
}
}
};
/**
* @define {boolean} Whether traces of {@code then} calls should be included in
* exceptions thrown
*/
goog.define('goog.Promise.LONG_STACK_TRACES', false);
/**
* @define {number} The delay in milliseconds before a rejected Promise's reason
* is passed to the rejection handler. By default, the rejection handler
* rethrows the rejection reason so that it appears in the developer console or
* {@code window.onerror} handler.
*
* Rejections are rethrown as quickly as possible by default. A negative value
* disables rejection handling entirely.
*/
goog.define('goog.Promise.UNHANDLED_REJECTION_DELAY', 0);
/**
* The possible internal states for a Promise. These states are not directly
* observable to external callers.
* @enum {number}
* @private
*/
goog.Promise.State_ = {
/** The Promise is waiting for resolution. */
PENDING: 0,
/** The Promise is blocked waiting for the result of another Thenable. */
BLOCKED: 1,
/** The Promise has been resolved with a fulfillment value. */
FULFILLED: 2,
/** The Promise has been resolved with a rejection reason. */
REJECTED: 3
};
/**
* Entries in the callback chain. Each call to {@code then},
* {@code thenCatch}, or {@code thenAlways} creates an entry containing the
* functions that may be invoked once the Promise is settled.
*
* @private @final @struct @constructor
*/
goog.Promise.CallbackEntry_ = function() {
/** @type {?goog.Promise} */
this.child = null;
/** @type {Function} */
this.onFulfilled = null;
/** @type {Function} */
this.onRejected = null;
/** @type {?} */
this.context = null;
/** @type {?goog.Promise.CallbackEntry_} */
this.next = null;
/**
* A boolean value to indicate this is a "thenAlways" callback entry.
* Unlike a normal "then/thenVoid" a "thenAlways doesn't participate
* in "cancel" considerations but is simply an observer and requires
* special handling.
* @type {boolean}
*/
this.always = false;
};
/** clear the object prior to reuse */
goog.Promise.CallbackEntry_.prototype.reset = function() {
this.child = null;
this.onFulfilled = null;
this.onRejected = null;
this.context = null;
this.always = false;
};
/**
* @define {number} The number of currently unused objects to keep around for
* reuse.
*/
goog.define('goog.Promise.DEFAULT_MAX_UNUSED', 100);
/** @const @private {goog.async.FreeList<!goog.Promise.CallbackEntry_>} */
goog.Promise.freelist_ = new goog.async.FreeList(
function() {
return new goog.Promise.CallbackEntry_();
},
function(item) {
item.reset();
},
goog.Promise.DEFAULT_MAX_UNUSED);
/**
* @param {Function} onFulfilled
* @param {Function} onRejected
* @param {?} context
* @return {!goog.Promise.CallbackEntry_}
* @private
*/
goog.Promise.getCallbackEntry_ = function(onFulfilled, onRejected, context) {
var entry = goog.Promise.freelist_.get();
entry.onFulfilled = onFulfilled;
entry.onRejected = onRejected;
entry.context = context;
return entry;
};
/**
* @param {!goog.Promise.CallbackEntry_} entry
* @private
*/
goog.Promise.returnEntry_ = function(entry) {
goog.Promise.freelist_.put(entry);
};
/**
* @param {(TYPE|goog.Thenable<TYPE>|Thenable)=} opt_value
* @return {!goog.Promise<TYPE>} A new Promise that is immediately resolved
* with the given value. If the input value is already a goog.Promise, it
* will be returned immediately without creating a new instance.
* @template TYPE
*/
goog.Promise.resolve = function(opt_value) {
if (opt_value instanceof goog.Promise) {
// Avoid creating a new object if we already have a promise object
// of the correct type.
return opt_value;
}
// Passing goog.nullFunction will cause the constructor to take an optimized
// path that skips calling the resolver function.
var promise = new goog.Promise(goog.nullFunction);
promise.resolve_(goog.Promise.State_.FULFILLED, opt_value);
return promise;
};
/**
* @param {*=} opt_reason
* @return {!goog.Promise} A new Promise that is immediately rejected with the
* given reason.
*/
goog.Promise.reject = function(opt_reason) {
return new goog.Promise(function(resolve, reject) {
reject(opt_reason);
});
};
/**
* This is identical to
* {@code goog.Promise.resolve(value).then(onFulfilled, onRejected)}, but it
* avoids creating an unnecessary wrapper Promise when {@code value} is already
* thenable.
*
* @param {?(goog.Thenable<TYPE>|Thenable|TYPE)} value
* @param {function(TYPE): ?} onFulfilled
* @param {function(*): *} onRejected
* @template TYPE
* @private
*/
goog.Promise.resolveThen_ = function(value, onFulfilled, onRejected) {
var isThenable = goog.Promise.maybeThen_(
value, onFulfilled, onRejected, null);
if (!isThenable) {
goog.async.run(goog.partial(onFulfilled, value));
}
};
/**
* @param {!Array<?(goog.Promise<TYPE>|goog.Thenable<TYPE>|Thenable|*)>}
* promises
* @return {!goog.Promise<TYPE>} A Promise that receives the result of the
* first Promise (or Promise-like) input to settle immediately after it
* settles.
* @template TYPE
*/
goog.Promise.race = function(promises) {
return new goog.Promise(function(resolve, reject) {
if (!promises.length) {
resolve(undefined);
}
for (var i = 0, promise; i < promises.length; i++) {
promise = promises[i];
goog.Promise.resolveThen_(promise, resolve, reject);
}
});
};
/**
* @param {!Array<?(goog.Promise<TYPE>|goog.Thenable<TYPE>|Thenable|*)>}
* promises
* @return {!goog.Promise<!Array<TYPE>>} A Promise that receives a list of
* every fulfilled value once every input Promise (or Promise-like) is
* successfully fulfilled, or is rejected with the first rejection reason
* immediately after it is rejected.
* @template TYPE
*/
goog.Promise.all = function(promises) {
return new goog.Promise(function(resolve, reject) {
var toFulfill = promises.length;
var values = [];
if (!toFulfill) {
resolve(values);
return;
}
var onFulfill = function(index, value) {
toFulfill--;
values[index] = value;
if (toFulfill == 0) {
resolve(values);
}
};
var onReject = function(reason) {
reject(reason);
};
for (var i = 0, promise; i < promises.length; i++) {
promise = promises[i];
goog.Promise.resolveThen_(
promise, goog.partial(onFulfill, i), onReject);
}
});
};
/**
* @param {!Array<?(goog.Promise<TYPE>|goog.Thenable<TYPE>|Thenable|*)>}
* promises
* @return {!goog.Promise<!Array<{
* fulfilled: boolean,
* value: (TYPE|undefined),
* reason: (*|undefined)}>>} A Promise that resolves with a list of
* result objects once all input Promises (or Promise-like) have
* settled. Each result object contains a 'fulfilled' boolean indicating
* whether an input Promise was fulfilled or rejected. For fulfilled
* Promises, the resulting value is stored in the 'value' field. For
* rejected Promises, the rejection reason is stored in the 'reason'
* field.
* @template TYPE
*/
goog.Promise.allSettled = function(promises) {
return new goog.Promise(function(resolve, reject) {
var toSettle = promises.length;
var results = [];
if (!toSettle) {
resolve(results);
return;
}
var onSettled = function(index, fulfilled, result) {
toSettle--;
results[index] = fulfilled ?
{fulfilled: true, value: result} :
{fulfilled: false, reason: result};
if (toSettle == 0) {
resolve(results);
}
};
for (var i = 0, promise; i < promises.length; i++) {
promise = promises[i];
goog.Promise.resolveThen_(promise,
goog.partial(onSettled, i, true /* fulfilled */),
goog.partial(onSettled, i, false /* fulfilled */));
}
});
};
/**
* @param {!Array<?(goog.Promise<TYPE>|goog.Thenable<TYPE>|Thenable|*)>}
* promises
* @return {!goog.Promise<TYPE>} A Promise that receives the value of the first
* input to be fulfilled, or is rejected with a list of every rejection
* reason if all inputs are rejected.
* @template TYPE
*/
goog.Promise.firstFulfilled = function(promises) {
return new goog.Promise(function(resolve, reject) {
var toReject = promises.length;
var reasons = [];
if (!toReject) {
resolve(undefined);
return;
}
var onFulfill = function(value) {
resolve(value);
};
var onReject = function(index, reason) {
toReject--;
reasons[index] = reason;
if (toReject == 0) {
reject(reasons);
}
};
for (var i = 0, promise; i < promises.length; i++) {
promise = promises[i];
goog.Promise.resolveThen_(
promise, onFulfill, goog.partial(onReject, i));
}
});
};
/**
* @return {!goog.promise.Resolver<TYPE>} Resolver wrapping the promise and its
* resolve / reject functions. Resolving or rejecting the resolver
* resolves or rejects the promise.
* @template TYPE
*/
goog.Promise.withResolver = function() {
var resolve, reject;
var promise = new goog.Promise(function(rs, rj) {
resolve = rs;
reject = rj;
});
return new goog.Promise.Resolver_(promise, resolve, reject);
};
/**
* Adds callbacks that will operate on the result of the Promise, returning a
* new child Promise.
*
* If the Promise is fulfilled, the {@code onFulfilled} callback will be invoked
* with the fulfillment value as argument, and the child Promise will be
* fulfilled with the return value of the callback. If the callback throws an
* exception, the child Promise will be rejected with the thrown value instead.
*
* If the Promise is rejected, the {@code onRejected} callback will be invoked
* with the rejection reason as argument, and the child Promise will be resolved
* with the return value or rejected with the thrown value of the callback.
*
* @override
*/
goog.Promise.prototype.then = function(
opt_onFulfilled, opt_onRejected, opt_context) {
if (opt_onFulfilled != null) {
goog.asserts.assertFunction(opt_onFulfilled,
'opt_onFulfilled should be a function.');
}
if (opt_onRejected != null) {
goog.asserts.assertFunction(opt_onRejected,
'opt_onRejected should be a function. Did you pass opt_context ' +
'as the second argument instead of the third?');
}
if (goog.Promise.LONG_STACK_TRACES) {
this.addStackTrace_(new Error('then'));
}
return this.addChildPromise_(
goog.isFunction(opt_onFulfilled) ? opt_onFulfilled : null,
goog.isFunction(opt_onRejected) ? opt_onRejected : null,
opt_context);
};
goog.Thenable.addImplementation(goog.Promise);
/**
* Adds callbacks that will operate on the result of the Promise without
* returning a child Promise (unlike "then").
*
* If the Promise is fulfilled, the {@code onFulfilled} callback will be invoked
* with the fulfillment value as argument.
*
* If the Promise is rejected, the {@code onRejected} callback will be invoked
* with the rejection reason as argument.
*
* @param {?(function(this:THIS, TYPE):?)=} opt_onFulfilled A
* function that will be invoked with the fulfillment value if the Promise
* is fulfilled.
* @param {?(function(this:THIS, *): *)=} opt_onRejected A function that will
* be invoked with the rejection reason if the Promise is rejected.
* @param {THIS=} opt_context An optional context object that will be the
* execution context for the callbacks. By default, functions are executed
* with the default this.
* @package
* @template THIS
*/
goog.Promise.prototype.thenVoid = function(
opt_onFulfilled, opt_onRejected, opt_context) {
if (opt_onFulfilled != null) {
goog.asserts.assertFunction(opt_onFulfilled,
'opt_onFulfilled should be a function.');
}
if (opt_onRejected != null) {
goog.asserts.assertFunction(opt_onRejected,
'opt_onRejected should be a function. Did you pass opt_context ' +
'as the second argument instead of the third?');
}
if (goog.Promise.LONG_STACK_TRACES) {
this.addStackTrace_(new Error('then'));
}
// Note: no default rejection handler is provided here as we need to
// distinguish unhandled rejections.
this.addCallbackEntry_(goog.Promise.getCallbackEntry_(
opt_onFulfilled || goog.nullFunction,
opt_onRejected || null,
opt_context));
};
/**
* Adds a callback that will be invoked when the Promise is settled (fulfilled
* or rejected). The callback receives no argument, and no new child Promise is
* created. This is useful for ensuring that cleanup takes place after certain
* asynchronous operations. Callbacks added with {@code thenAlways} will be
* executed in the same order with other calls to {@code then},
* {@code thenAlways}, or {@code thenCatch}.
*
* Since it does not produce a new child Promise, cancellation propagation is
* not prevented by adding callbacks with {@code thenAlways}. A Promise that has
* a cleanup handler added with {@code thenAlways} will be canceled if all of
* its children created by {@code then} (or {@code thenCatch}) are canceled.
* Additionally, since any rejections are not passed to the callback, it does
* not stop the unhandled rejection handler from running.
*
* @param {function(this:THIS): void} onSettled A function that will be invoked
* when the Promise is settled (fulfilled or rejected).
* @param {THIS=} opt_context An optional context object that will be the
* execution context for the callbacks. By default, functions are executed
* in the global scope.
* @return {!goog.Promise<TYPE>} This Promise, for chaining additional calls.
* @template THIS
*/
goog.Promise.prototype.thenAlways = function(onSettled, opt_context) {
if (goog.Promise.LONG_STACK_TRACES) {
this.addStackTrace_(new Error('thenAlways'));
}
var entry = goog.Promise.getCallbackEntry_(onSettled, onSettled, opt_context);
entry.always = true;
this.addCallbackEntry_(entry);
return this;
};
/**
* Adds a callback that will be invoked only if the Promise is rejected. This
* is equivalent to {@code then(null, onRejected)}.
*
* @param {!function(this:THIS, *): *} onRejected A function that will be
* invoked with the rejection reason if the Promise is rejected.
* @param {THIS=} opt_context An optional context object that will be the
* execution context for the callbacks. By default, functions are executed
* in the global scope.
* @return {!goog.Promise} A new Promise that will receive the result of the
* callback.
* @template THIS
*/
goog.Promise.prototype.thenCatch = function(onRejected, opt_context) {
if (goog.Promise.LONG_STACK_TRACES) {
this.addStackTrace_(new Error('thenCatch'));
}
return this.addChildPromise_(null, onRejected, opt_context);
};
/**
* Cancels the Promise if it is still pending by rejecting it with a cancel
* Error. No action is performed if the Promise is already resolved.
*
* All child Promises of the canceled Promise will be rejected with the same
* cancel error, as with normal Promise rejection. If the Promise to be canceled
* is the only child of a pending Promise, the parent Promise will also be
* canceled. Cancellation may propagate upward through multiple generations.
*
* @param {string=} opt_message An optional debugging message for describing the
* cancellation reason.
*/
goog.Promise.prototype.cancel = function(opt_message) {
if (this.state_ == goog.Promise.State_.PENDING) {
goog.async.run(function() {
var err = new goog.Promise.CancellationError(opt_message);
this.cancelInternal_(err);
}, this);
}
};
/**
* Cancels this Promise with the given error.
*
* @param {!Error} err The cancellation error.
* @private
*/
goog.Promise.prototype.cancelInternal_ = function(err) {
if (this.state_ == goog.Promise.State_.PENDING) {
if (this.parent_) {
// Cancel the Promise and remove it from the parent's child list.
this.parent_.cancelChild_(this, err);
this.parent_ = null;
} else {
this.resolve_(goog.Promise.State_.REJECTED, err);
}
}
};
/**
* Cancels a child Promise from the list of callback entries. If the Promise has
* not already been resolved, reject it with a cancel error. If there are no
* other children in the list of callback entries, propagate the cancellation
* by canceling this Promise as well.
*
* @param {!goog.Promise} childPromise The Promise to cancel.
* @param {!Error} err The cancel error to use for rejecting the Promise.
* @private
*/
goog.Promise.prototype.cancelChild_ = function(childPromise, err) {
if (!this.callbackEntries_) {
return;
}
var childCount = 0;
var childEntry = null;
var beforeChildEntry = null;
// Find the callback entry for the childPromise, and count whether there are
// additional child Promises.
for (var entry = this.callbackEntries_; entry; entry = entry.next) {
if (!entry.always) {
childCount++;
if (entry.child == childPromise) {
childEntry = entry;
}
if (childEntry && childCount > 1) {
break;
}
}
if (!childEntry) {
beforeChildEntry = entry;
}
}
// Can a child entry be missing?
// If the child Promise was the only child, cancel this Promise as well.
// Otherwise, reject only the child Promise with the cancel error.
if (childEntry) {
if (this.state_ == goog.Promise.State_.PENDING && childCount == 1) {
this.cancelInternal_(err);
} else {
if (beforeChildEntry) {
this.removeEntryAfter_(beforeChildEntry);
} else {
this.popEntry_();
}
this.executeCallback_(
childEntry, goog.Promise.State_.REJECTED, err);
}
}
};
/**
* Adds a callback entry to the current Promise, and schedules callback
* execution if the Promise has already been settled.
*
* @param {goog.Promise.CallbackEntry_} callbackEntry Record containing
* {@code onFulfilled} and {@code onRejected} callbacks to execute after
* the Promise is settled.
* @private
*/
goog.Promise.prototype.addCallbackEntry_ = function(callbackEntry) {
if (!this.hasEntry_() &&
(this.state_ == goog.Promise.State_.FULFILLED ||
this.state_ == goog.Promise.State_.REJECTED)) {
this.scheduleCallbacks_();
}
this.queueEntry_(callbackEntry);
};
/**
* Creates a child Promise and adds it to the callback entry list. The result of
* the child Promise is determined by the state of the parent Promise and the
* result of the {@code onFulfilled} or {@code onRejected} callbacks as
* specified in the Promise resolution procedure.
*
* @see http://promisesaplus.com/#the__method
*
* @param {?function(this:THIS, TYPE):
* (RESULT|goog.Promise<RESULT>|Thenable)} onFulfilled A callback that
* will be invoked if the Promise is fullfilled, or null.
* @param {?function(this:THIS, *): *} onRejected A callback that will be
* invoked if the Promise is rejected, or null.
* @param {THIS=} opt_context An optional execution context for the callbacks.
* in the default calling context.
* @return {!goog.Promise} The child Promise.
* @template RESULT,THIS
* @private
*/
goog.Promise.prototype.addChildPromise_ = function(
onFulfilled, onRejected, opt_context) {
/** @type {goog.Promise.CallbackEntry_} */
var callbackEntry = goog.Promise.getCallbackEntry_(null, null, null);
callbackEntry.child = new goog.Promise(function(resolve, reject) {
// Invoke onFulfilled, or resolve with the parent's value if absent.
callbackEntry.onFulfilled = onFulfilled ? function(value) {
try {
var result = onFulfilled.call(opt_context, value);
resolve(result);
} catch (err) {
reject(err);
}
} : resolve;
// Invoke onRejected, or reject with the parent's reason if absent.
callbackEntry.onRejected = onRejected ? function(reason) {
try {
var result = onRejected.call(opt_context, reason);
if (!goog.isDef(result) &&
reason instanceof goog.Promise.CancellationError) {
// Propagate cancellation to children if no other result is returned.
reject(reason);
} else {
resolve(result);
}
} catch (err) {
reject(err);
}
} : reject;
});
callbackEntry.child.parent_ = this;
this.addCallbackEntry_(callbackEntry);
return callbackEntry.child;
};
/**
* Unblocks the Promise and fulfills it with the given value.
*
* @param {TYPE} value
* @private
*/
goog.Promise.prototype.unblockAndFulfill_ = function(value) {
goog.asserts.assert(this.state_ == goog.Promise.State_.BLOCKED);
this.state_ = goog.Promise.State_.PENDING;
this.resolve_(goog.Promise.State_.FULFILLED, value);
};
/**
* Unblocks the Promise and rejects it with the given rejection reason.
*
* @param {*} reason
* @private
*/
goog.Promise.prototype.unblockAndReject_ = function(reason) {
goog.asserts.assert(this.state_ == goog.Promise.State_.BLOCKED);
this.state_ = goog.Promise.State_.PENDING;
this.resolve_(goog.Promise.State_.REJECTED, reason);
};
/**
* Attempts to resolve a Promise with a given resolution state and value. This
* is a no-op if the given Promise has already been resolved.
*
* If the given result is a Thenable (such as another Promise), the Promise will
* be settled with the same state and result as the Thenable once it is itself
* settled.
*
* If the given result is not a Thenable, the Promise will be settled (fulfilled
* or rejected) with that result based on the given state.
*
* @see http://promisesaplus.com/#the_promise_resolution_procedure
*
* @param {goog.Promise.State_} state
* @param {*} x The result to apply to the Promise.
* @private
*/
goog.Promise.prototype.resolve_ = function(state, x) {
if (this.state_ != goog.Promise.State_.PENDING) {
return;
}
if (this == x) {
state = goog.Promise.State_.REJECTED;
x = new TypeError('Promise cannot resolve to itself');
}
this.state_ = goog.Promise.State_.BLOCKED;
var isThenable = goog.Promise.maybeThen_(
x, this.unblockAndFulfill_, this.unblockAndReject_, this);
if (isThenable) {
return;
}
this.result_ = x;
this.state_ = state;
// Since we can no longer be canceled, remove link to parent, so that the
// child promise does not keep the parent promise alive.
this.parent_ = null;
this.scheduleCallbacks_();
if (state == goog.Promise.State_.REJECTED &&
!(x instanceof goog.Promise.CancellationError)) {
goog.Promise.addUnhandledRejection_(this, x);
}
};
/**
* Invokes the "then" method of an input value if that value is a Thenable. This
* is a no-op if the value is not thenable.
*
* @param {*} value A potentially thenable value.
* @param {!Function} onFulfilled
* @param {!Function} onRejected
* @param {*} context
* @return {boolean} Whether the input value was thenable.
* @private
*/
goog.Promise.maybeThen_ = function(value, onFulfilled, onRejected, context) {
if (value instanceof goog.Promise) {
value.thenVoid(onFulfilled, onRejected, context);
return true;
} else if (goog.Thenable.isImplementedBy(value)) {
value = /** @type {!goog.Thenable} */ (value);
value.then(onFulfilled, onRejected, context);
return true;
} else if (goog.isObject(value)) {
try {
var then = value['then'];
if (goog.isFunction(then)) {
goog.Promise.tryThen_(
value, then, onFulfilled, onRejected, context);
return true;
}
} catch (e) {
onRejected.call(context, e);
return true;
}
}
return false;
};
/**
* Attempts to call the {@code then} method on an object in the hopes that it is
* a Promise-compatible instance. This allows interoperation between different
* Promise implementations, however a non-compliant object may cause a Promise
* to hang indefinitely. If the {@code then} method throws an exception, the
* dependent Promise will be rejected with the thrown value.
*
* @see http://promisesaplus.com/#point-70
*
* @param {Thenable} thenable An object with a {@code then} method that may be
* compatible with the Promise/A+ specification.
* @param {!Function} then The {@code then} method of the Thenable object.
* @param {!Function} onFulfilled
* @param {!Function} onRejected
* @param {*} context
* @private
*/
goog.Promise.tryThen_ = function(
thenable, then, onFulfilled, onRejected, context) {
var called = false;
var resolve = function(value) {
if (!called) {
called = true;
onFulfilled.call(context, value);
}
};
var reject = function(reason) {
if (!called) {
called = true;
onRejected.call(context, reason);
}
};
try {
then.call(thenable, resolve, reject);
} catch (e) {
reject(e);
}
};
/**
* Executes the pending callbacks of a settled Promise after a timeout.
*
* Section 2.2.4 of the Promises/A+ specification requires that Promise
* callbacks must only be invoked from a call stack that only contains Promise
* implementation code, which we accomplish by invoking callback execution after
* a timeout. If {@code startExecution_} is called multiple times for the same
* Promise, the callback chain will be evaluated only once. Additional callbacks
* may be added during the evaluation phase, and will be executed in the same
* event loop.
*
* All Promises added to the waiting list during the same browser event loop
* will be executed in one batch to avoid using a separate timeout per Promise.
*
* @private
*/
goog.Promise.prototype.scheduleCallbacks_ = function() {
if (!this.executing_) {
this.executing_ = true;
goog.async.run(this.executeCallbacks_, this);
}
};
/**
* @return {boolean} Whether there are any pending callbacks queued.
* @private
*/
goog.Promise.prototype.hasEntry_ = function() {
return !!this.callbackEntries_;
};
/**
* @param {goog.Promise.CallbackEntry_} entry
* @private
*/
goog.Promise.prototype.queueEntry_ = function(entry) {
goog.asserts.assert(entry.onFulfilled != null);
if (this.callbackEntriesTail_) {
this.callbackEntriesTail_.next = entry;
this.callbackEntriesTail_ = entry;
} else {
// It the work queue was empty set the head too.
this.callbackEntries_ = entry;
this.callbackEntriesTail_ = entry;
}
};
/**
* @return {goog.Promise.CallbackEntry_} entry
* @private
*/
goog.Promise.prototype.popEntry_ = function() {
var entry = null;
if (this.callbackEntries_) {
entry = this.callbackEntries_;
this.callbackEntries_ = entry.next;
entry.next = null;
}
// It the work queue is empty clear the tail too.
if (!this.callbackEntries_) {
this.callbackEntriesTail_ = null;
}
if (entry != null) {
goog.asserts.assert(entry.onFulfilled != null);
}
return entry;
};
/**
* @param {goog.Promise.CallbackEntry_} previous
* @private
*/
goog.Promise.prototype.removeEntryAfter_ = function(previous) {
goog.asserts.assert(this.callbackEntries_);
goog.asserts.assert(previous != null);
// If the last entry is being removed, update the tail
if (previous.next == this.callbackEntriesTail_) {
this.callbackEntriesTail_ = previous;
}
previous.next = previous.next.next;
};
/**
* Executes all pending callbacks for this Promise.
*
* @private
*/
goog.Promise.prototype.executeCallbacks_ = function() {
var entry = null;
while (entry = this.popEntry_()) {
if (goog.Promise.LONG_STACK_TRACES) {
this.currentStep_++;
}
this.executeCallback_(entry, this.state_, this.result_);
}
this.executing_ = false;
};
/**
* Executes a pending callback for this Promise. Invokes an {@code onFulfilled}
* or {@code onRejected} callback based on the settled state of the Promise.
*
* @param {!goog.Promise.CallbackEntry_} callbackEntry An entry containing the
* onFulfilled and/or onRejected callbacks for this step.
* @param {goog.Promise.State_} state The resolution status of the Promise,
* either FULFILLED or REJECTED.
* @param {*} result The settled result of the Promise.
* @private
*/
goog.Promise.prototype.executeCallback_ = function(
callbackEntry, state, result) {
// Cancel an unhandled rejection if the then/thenVoid call had an onRejected.
if (state == goog.Promise.State_.REJECTED &&
callbackEntry.onRejected && !callbackEntry.always) {
this.removeUnhandledRejection_();
}
if (callbackEntry.child) {
// When the parent is settled, the child no longer needs to hold on to it,
// as the parent can no longer be canceled.
callbackEntry.child.parent_ = null;
goog.Promise.invokeCallback_(callbackEntry, state, result);
} else {
// Callbacks created with thenAlways or thenVoid do not have the rejection
// handling code normally set up in the child Promise.
try {
callbackEntry.always ?
callbackEntry.onFulfilled.call(callbackEntry.context) :
goog.Promise.invokeCallback_(callbackEntry, state, result);
} catch (err) {
goog.Promise.handleRejection_.call(null, err);
}
}
goog.Promise.returnEntry_(callbackEntry);
};
/**
* Executes the onFulfilled or onRejected callback for a callbackEntry.
*
* @param {!goog.Promise.CallbackEntry_} callbackEntry
* @param {goog.Promise.State_} state
* @param {*} result
* @private
*/
goog.Promise.invokeCallback_ = function(callbackEntry, state, result) {
if (state == goog.Promise.State_.FULFILLED) {
callbackEntry.onFulfilled.call(callbackEntry.context, result);
} else if (callbackEntry.onRejected) {
callbackEntry.onRejected.call(callbackEntry.context, result);
}
};
/**
* Records a stack trace entry for functions that call {@code then} or the
* Promise constructor. May be disabled by unsetting {@code LONG_STACK_TRACES}.
*
* @param {!Error} err An Error object created by the calling function for
* providing a stack trace.
* @private
*/
goog.Promise.prototype.addStackTrace_ = function(err) {
if (goog.Promise.LONG_STACK_TRACES && goog.isString(err.stack)) {
// Extract the third line of the stack trace, which is the entry for the
// user function that called into Promise code.
var trace = err.stack.split('\n', 4)[3];
var message = err.message;
// Pad the message to align the traces.
message += Array(11 - message.length).join(' ');
this.stack_.push(message + trace);
}
};
/**
* Adds extra stack trace information to an exception for the list of
* asynchronous {@code then} calls that have been run for this Promise. Stack
* trace information is recorded in {@see #addStackTrace_}, and appended to
* rethrown errors when {@code LONG_STACK_TRACES} is enabled.
*
* @param {*} err An unhandled exception captured during callback execution.
* @private
*/
goog.Promise.prototype.appendLongStack_ = function(err) {
if (goog.Promise.LONG_STACK_TRACES &&
err && goog.isString(err.stack) && this.stack_.length) {
var longTrace = ['Promise trace:'];
for (var promise = this; promise; promise = promise.parent_) {
for (var i = this.currentStep_; i >= 0; i--) {
longTrace.push(promise.stack_[i]);
}
longTrace.push('Value: ' +
'[' + (promise.state_ == goog.Promise.State_.REJECTED ?
'REJECTED' : 'FULFILLED') + '] ' +
'<' + String(promise.result_) + '>');
}
err.stack += '\n\n' + longTrace.join('\n');
}
};
/**
* Marks this rejected Promise as having being handled. Also marks any parent
* Promises in the rejected state as handled. The rejection handler will no
* longer be invoked for this Promise (if it has not been called already).
*
* @private
*/
goog.Promise.prototype.removeUnhandledRejection_ = function() {
if (goog.Promise.UNHANDLED_REJECTION_DELAY > 0) {
for (var p = this; p && p.unhandledRejectionId_; p = p.parent_) {
goog.global.clearTimeout(p.unhandledRejectionId_);
p.unhandledRejectionId_ = 0;
}
} else if (goog.Promise.UNHANDLED_REJECTION_DELAY == 0) {
for (var p = this; p && p.hadUnhandledRejection_; p = p.parent_) {
p.hadUnhandledRejection_ = false;
}
}
};
/**
* Marks this rejected Promise as unhandled. If no {@code onRejected} callback
* is called for this Promise before the {@code UNHANDLED_REJECTION_DELAY}
* expires, the reason will be passed to the unhandled rejection handler. The
* handler typically rethrows the rejection reason so that it becomes visible in
* the developer console.
*
* @param {!goog.Promise} promise The rejected Promise.
* @param {*} reason The Promise rejection reason.
* @private
*/
goog.Promise.addUnhandledRejection_ = function(promise, reason) {
if (goog.Promise.UNHANDLED_REJECTION_DELAY > 0) {
promise.unhandledRejectionId_ = goog.global.setTimeout(function() {
promise.appendLongStack_(reason);
goog.Promise.handleRejection_.call(null, reason);
}, goog.Promise.UNHANDLED_REJECTION_DELAY);
} else if (goog.Promise.UNHANDLED_REJECTION_DELAY == 0) {
promise.hadUnhandledRejection_ = true;
goog.async.run(function() {
if (promise.hadUnhandledRejection_) {
promise.appendLongStack_(reason);
goog.Promise.handleRejection_.call(null, reason);
}
});
}
};
/**
* A method that is invoked with the rejection reasons for Promises that are
* rejected but have no {@code onRejected} callbacks registered yet.
* @type {function(*)}
* @private
*/
goog.Promise.handleRejection_ = goog.async.throwException;
/**
* Sets a handler that will be called with reasons from unhandled rejected
* Promises. If the rejected Promise (or one of its descendants) has an
* {@code onRejected} callback registered, the rejection will be considered
* handled, and the rejection handler will not be called.
*
* By default, unhandled rejections are rethrown so that the error may be
* captured by the developer console or a {@code window.onerror} handler.
*
* @param {function(*)} handler A function that will be called with reasons from
* rejected Promises. Defaults to {@code goog.async.throwException}.
*/
goog.Promise.setUnhandledRejectionHandler = function(handler) {
goog.Promise.handleRejection_ = handler;
};
/**
* Error used as a rejection reason for canceled Promises.
*
* @param {string=} opt_message
* @constructor
* @extends {goog.debug.Error}
* @final
*/
goog.Promise.CancellationError = function(opt_message) {
goog.Promise.CancellationError.base(this, 'constructor', opt_message);
};
goog.inherits(goog.Promise.CancellationError, goog.debug.Error);
/** @override */
goog.Promise.CancellationError.prototype.name = 'cancel';
/**
* Internal implementation of the resolver interface.
*
* @param {!goog.Promise<TYPE>} promise
* @param {function((TYPE|goog.Promise<TYPE>|Thenable)=)} resolve
* @param {function(*=): void} reject
* @implements {goog.promise.Resolver<TYPE>}
* @final @struct
* @constructor
* @private
* @template TYPE
*/
goog.Promise.Resolver_ = function(promise, resolve, reject) {
/** @const */
this.promise = promise;
/** @const */
this.resolve = resolve;
/** @const */
this.reject = reject;
};
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