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/**
* slice() reference.
*/
var slice = Array.prototype.slice;
/**
* Expose `co`.
*/
module.exports = co['default'] = co.co = co;
/**
* Wrap the given generator `fn` into a
* function that returns a promise.
* This is a separate function so that
* every `co()` call doesn't create a new,
* unnecessary closure.
*
* @param {GeneratorFunction} fn
* @return {Function}
* @api public
*/
co.wrap = function (fn) {
createPromise.__generatorFunction__ = fn;
return createPromise;
function createPromise() {
return co.call(this, fn.apply(this, arguments));
}
};
/**
* Execute the generator function or a generator
* and return a promise.
*
* @param {Function} fn
* @return {Promise}
* @api public
*/
function co(gen) {
var ctx = this;
var args = slice.call(arguments, 1)
// we wrap everything in a promise to avoid promise chaining,
// which leads to memory leak errors.
// see https://github.com/tj/co/issues/180
return new Promise(function(resolve, reject) {
if (typeof gen === 'function') gen = gen.apply(ctx, args);
if (!gen || typeof gen.next !== 'function') return resolve(gen);
onFulfilled();
/**
* @param {Mixed} res
* @return {Promise}
* @api private
*/
function onFulfilled(res) {
var ret;
try {
ret = gen.next(res);
} catch (e) {
return reject(e);
}
next(ret);
}
/**
* @param {Error} err
* @return {Promise}
* @api private
*/
function onRejected(err) {
var ret;
try {
ret = gen.throw(err);
} catch (e) {
return reject(e);
}
next(ret);
}
/**
* Get the next value in the generator,
* return a promise.
*
* @param {Object} ret
* @return {Promise}
* @api private
*/
function next(ret) {
if (ret.done) return resolve(ret.value);
var value = toPromise.call(ctx, ret.value);
if (value && isPromise(value)) return value.then(onFulfilled, onRejected);
return onRejected(new TypeError('You may only yield a function, promise, generator, array, or object, '
+ 'but the following object was passed: "' + String(ret.value) + '"'));
}
});
}
/**
* Convert a `yield`ed value into a promise.
*
* @param {Mixed} obj
* @return {Promise}
* @api private
*/
function toPromise(obj) {
if (!obj) return obj;
if (isPromise(obj)) return obj;
if (isGeneratorFunction(obj) || isGenerator(obj)) return co.call(this, obj);
if ('function' == typeof obj) return thunkToPromise.call(this, obj);
if (Array.isArray(obj)) return arrayToPromise.call(this, obj);
if (isObject(obj)) return objectToPromise.call(this, obj);
return obj;
}
/**
* Convert a thunk to a promise.
*
* @param {Function}
* @return {Promise}
* @api private
*/
function thunkToPromise(fn) {
var ctx = this;
return new Promise(function (resolve, reject) {
fn.call(ctx, function (err, res) {
if (err) return reject(err);
if (arguments.length > 2) res = slice.call(arguments, 1);
resolve(res);
});
});
}
/**
* Convert an array of "yieldables" to a promise.
* Uses `Promise.all()` internally.
*
* @param {Array} obj
* @return {Promise}
* @api private
*/
function arrayToPromise(obj) {
return Promise.all(obj.map(toPromise, this));
}
/**
* Convert an object of "yieldables" to a promise.
* Uses `Promise.all()` internally.
*
* @param {Object} obj
* @return {Promise}
* @api private
*/
function objectToPromise(obj){
var results = new obj.constructor();
var keys = Object.keys(obj);
var promises = [];
for (var i = 0; i < keys.length; i++) {
var key = keys[i];
var promise = toPromise.call(this, obj[key]);
if (promise && isPromise(promise)) defer(promise, key);
else results[key] = obj[key];
}
return Promise.all(promises).then(function () {
return results;
});
function defer(promise, key) {
// predefine the key in the result
results[key] = undefined;
promises.push(promise.then(function (res) {
results[key] = res;
}));
}
}
/**
* Check if `obj` is a promise.
*
* @param {Object} obj
* @return {Boolean}
* @api private
*/
function isPromise(obj) {
return 'function' == typeof obj.then;
}
/**
* Check if `obj` is a generator.
*
* @param {Mixed} obj
* @return {Boolean}
* @api private
*/
function isGenerator(obj) {
return 'function' == typeof obj.next && 'function' == typeof obj.throw;
}
/**
* Check if `obj` is a generator function.
*
* @param {Mixed} obj
* @return {Boolean}
* @api private
*/
function isGeneratorFunction(obj) {
var constructor = obj.constructor;
if (!constructor) return false;
if ('GeneratorFunction' === constructor.name || 'GeneratorFunction' === constructor.displayName) return true;
return isGenerator(constructor.prototype);
}
/**
* Check for plain object.
*
* @param {Mixed} val
* @return {Boolean}
* @api private
*/
function isObject(val) {
return Object == val.constructor;
}
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