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Draft support for WeakMap
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@kriskowal
kriskowal committed Oct 30, 2013
1 parent b71dc21 commit a5233e6
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10 changes: 8 additions & 2 deletions CHANGES.md
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,12 @@
`release/q.js`, which is suitable for use as a `<script>`, and
`release/amd/q.js`, which is suitable for use as an AMD module. All
new versions will be published to S3.
- :warning: Q now depends on an ASAP package and a WeakMap shim. If
you are using an AMD loader, you will need to bring in
https://github.com/kriskowal/asap and
https://github.com/drses/weak-map. If you are using Q as a
`<script>`, this has been embedded in the release. If you are using
Q in Node.js, the dependency is taken care of by NPM.
- :warning: Q now depends on a WeakMap shim. If you are using an AMD
loader, you will need to bring in https://github.com/drses/weak-map.
If you are using Q as a `<script>`, this has been embedded in the
Expand All @@ -24,8 +30,8 @@
- :warning: Withdrew support for SpiderMonkey style generators.
- :warning: `Q.all` no longer reuses the input array for the output
array.
- :warning: `Q.nextTick` is no longer supported. Please use `asap`
from the `asap` package directly.
- :warning: `valueOf` has been removed. Please use `inspect().value`
instead.

## 0.9.7

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3 changes: 2 additions & 1 deletion package.json
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Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,8 @@
"teleport": ">=0.2.0"
},
"dependencies": {
"asap": "~1.0.0"
"asap": "~1.0.0",
"weak-map": "~1.0.0"
},
"devDependencies": {
"jshint": "~2.1.9",
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196 changes: 83 additions & 113 deletions q.js
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Original file line number Diff line number Diff line change
Expand Up @@ -39,36 +39,12 @@ try {
var qStartingLine = captureLine();
var qFileName;

// shims
var asap = require("asap");
var WeakMap = require("weak-map");

// used for fallback in "allResolved"
var noop = function () {};

var asap = require("asap");

// Attempt to make generics safe in the face of downstream
// modifications.
// There is no situation where this is necessary.
// If you need a security guarantee, these primordials need to be
// deeply frozen anyway, and if you don’t need a security guarantee,
// this is just plain paranoid.
// However, this does have the nice side-effect of reducing the size
// of the code by reducing x.call() to merely x(), eliminating many
// hard-to-minify characters.
// See Mark Miller’s explanation of what this does.
// http://wiki.ecmascript.org/doku.php?id=conventions:safe_meta_programming
var call = Function.call;
function uncurryThis(f) {
return function () {
return call.apply(f, arguments);
};
}
// This is equivalent, but slower:
// uncurryThis = Function_bind.bind(Function_bind.call);
// http://jsperf.com/uncurrythis

var array_slice = uncurryThis(Array.prototype.slice);

var object_create = Object.create || function (prototype) {
function Type() { }
Type.prototype = prototype;
Expand All @@ -94,7 +70,7 @@ function makeStackTraceLong(error, promise) {
error.stack.indexOf(STACK_JUMP_SEPARATOR) === -1
) {
var stacks = [];
for (var p = promise; !!p; p = p.source) {
for (var p = promise; !!p; p = handlers.get(p).became) {
if (p.stack) {
stacks.unshift(p.stack);
}
Expand Down Expand Up @@ -193,8 +169,9 @@ function deprecate(callback, name, alternative) {
};
}

// end of shims
// beginning of real work
// end of long stack traces

var handlers = new WeakMap();

/**
* Constructs a promise for an immediate reference, passes promises through, or
Expand All @@ -218,6 +195,32 @@ function Q(value) {
}
Q.resolve = Q;

/**
* TODO
*/
function getHandler(promise) {
var handler = handlers.get(promise);
if (!handler || !handler.became) {
return handler;
}
handler = followHandler(handler);
handlers.set(promise, handler);
return handler;
}

function followHandler(handler) {
if (!handler.became) {
return handler;
} else {
handler.became = followHandler(handler.became);
return handler.became;
}
}

var theViciousCycleError = new Error("Can't resolve a promise with itself");
var theViciousCycleRejection = reject(theViciousCycleError);
var theViciousCycleHandler = getHandler(theViciousCycleRejection);

/**
* Controls whether or not long stack traces will be on
*/
Expand All @@ -241,44 +244,25 @@ function defer() {
// forward to the resolved promise. We coerce the resolution value to a
// promise using the `resolve` function because it handles both fully
// non-thenable values and other thenables gracefully.
var messages = [], progressListeners = [], resolvedPromise;
var messages = [], progressListeners = [];

var deferred = object_create(defer.prototype);
var promise = object_create(Promise.prototype);

promise.promiseDispatch = function (resolve, op, operands) {
var args = array_slice(arguments);
if (messages) {
messages.push(args);
var handler = {
dispatch: function (resolve, op, operands) {
messages.push([resolve, op, operands]);
if (op === "when" && operands[1]) { // progress operand
progressListeners.push(operands[1]);
}
} else {
asap(function () {
resolvedPromise.promiseDispatch.apply(resolvedPromise, args);
});
}
};

// XXX deprecated
promise.valueOf = deprecate(function () {
if (messages) {
return promise;
}
var nearerValue = nearer(resolvedPromise);
if (isPromise(nearerValue)) {
resolvedPromise = nearerValue; // shorten chain
}
return nearerValue;
}, "valueOf", "inspect");

promise.inspect = function () {
if (!resolvedPromise) {
},
inspect: function () {
return { state: "pending" };
}
return resolvedPromise.inspect();
};

handlers.set(promise, handler);

if (Q.longStackSupport && hasStacks) {
try {
throw new Error();
Expand All @@ -293,17 +277,20 @@ function defer() {
}
}

// NOTE: we do the checks for `resolvedPromise` in each method, instead of
// consolidating them into `become`, since otherwise we'd create new
// promises with the lines `become(whatever(value))`. See e.g. GH-252.

function become(newPromise) {
resolvedPromise = newPromise;
promise.source = newPromise;
handler.became = theViciousCycleHandler;
var newHandler = getHandler(newPromise);
handler.became = newHandler;

handlers.set(promise, newHandler);
handler = void 0; // A dead resolver should not retain dead objects
promise = void 0;

messages.forEach(function (message) {
// TODO figure out whether this asap is necessary. makeQ does not
// have it.
asap(function () {
newPromise.promiseDispatch.apply(newPromise, message);
newHandler.dispatch.apply(void 0, message);
});
});

Expand All @@ -312,30 +299,25 @@ function defer() {
}

deferred.promise = promise;

deferred.resolve = function (value) {
if (resolvedPromise) {
if (!messages) {
return;
}

become(Q(value));
};

deferred.fulfill = function (value) {
if (resolvedPromise) {
return;
}

become(fulfill(value));
};
deferred.reject = function (reason) {
if (resolvedPromise) {
if (!messages) {
return;
}

become(reject(reason));
};

deferred.notify = function (progress) {
if (resolvedPromise) {
if (!messages) {
return;
}

Expand Down Expand Up @@ -477,44 +459,34 @@ function Promise(descriptor, fallback, inspect) {

var promise = object_create(Promise.prototype);

promise.promiseDispatch = function (resolve, op, args) {
var result;
try {
if (descriptor[op]) {
result = descriptor[op].apply(promise, args);
} else {
result = fallback.call(promise, op, args);
var handler = {
dispatch: function (resolve, op, operands) {
var result;
try {
if (descriptor[op]) {
result = descriptor[op].apply(promise, operands);
} else {
result = fallback.call(promise, op, operands);
}
} catch (exception) {
result = reject(exception);
}
} catch (exception) {
result = reject(exception);
}
if (resolve) {
resolve(result);
}
if (resolve) {
resolve(result);
}
},
inspect: inspect
};

promise.inspect = inspect;

// XXX deprecated `valueOf` and `exception` support
if (inspect) {
var inspected = inspect();
if (inspected.state === "rejected") {
promise.exception = inspected.reason;
}

promise.valueOf = deprecate(function () {
var inspected = inspect();
if (inspected.state === "pending" ||
inspected.state === "rejected") {
return promise;
}
return inspected.value;
});
}
handlers.set(promise, handler);

return promise;
}

Promise.prototype.inspect = function () {
return getHandler(this).inspect();
};

Promise.prototype.toString = function () {
return "[object Promise]";
};
Expand Down Expand Up @@ -550,7 +522,7 @@ Promise.prototype.then = function (fulfilled, rejected, progressed) {
}

asap(function () {
self.promiseDispatch(function (value) {
getHandler(self).dispatch(function (value) {
if (done) {
return;
}
Expand All @@ -568,7 +540,7 @@ Promise.prototype.then = function (fulfilled, rejected, progressed) {
});

// Progress propagator need to be attached in the current tick.
self.promiseDispatch(void 0, "when", [void 0, function (value) {
getHandler(this).dispatch(void 0, "when", [void 0, function (value) {
var newValue;
var threw = false;
try {
Expand Down Expand Up @@ -655,9 +627,7 @@ function nearer(value) {
*/
Q.isPromise = isPromise;
function isPromise(object) {
return isObject(object) &&
typeof object.promiseDispatch === "function" &&
typeof object.inspect === "function";
return isObject(object) && !!handlers.get(object);
}

Q.isPromiseAlike = isPromiseAlike;
Expand All @@ -671,11 +641,11 @@ function isPromiseAlike(object) {
*/
Q.isPending = isPending;
function isPending(object) {
return isPromise(object) && object.inspect().state === "pending";
return Q(object).isPending();
}

Promise.prototype.isPending = function () {
return this.inspect().state === "pending";
return getHandler(this).inspect().state === "pending";
};

/**
Expand Down Expand Up @@ -1018,10 +988,10 @@ function dispatch(object, op, args) {
}

Promise.prototype.dispatch = function (op, args) {
var self = this;
var deferred = defer();
var self = this;
asap(function () {
self.promiseDispatch(deferred.resolve, op, args);
getHandler(self).dispatch(deferred.resolve, op, args);
});
return deferred.promise;
};
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