es6.promise.js

'use strict';
var $          = require('./$')
  , LIBRARY    = require('./$.library')
  , global     = require('./$.global')
  , ctx        = require('./$.ctx')
  , classof    = require('./$.classof')
  , $def       = require('./$.def')
  , isObject   = require('./$.is-object')
  , anObject   = require('./$.an-object')
  , aFunction  = require('./$.a-function')
  , strictNew  = require('./$.strict-new')
  , forOf      = require('./$.for-of')
  , setProto   = require('./$.set-proto').set
  , same       = require('./$.same')
  , species    = require('./$.species')
  , SPECIES    = require('./$.wks')('species')
  , RECORD     = require('./$.uid')('record')
  , asap       = require('./$.microtask')
  , PROMISE    = 'Promise'
  , process    = global.process
  , isNode     = classof(process) == 'process'
  , P          = global[PROMISE]
  , Wrapper;

var testResolve = function(sub){
  var test = new P(function(){});
  if(sub)test.constructor = Object;
  return P.resolve(test) === test;
};

var useNative = function(){
  var works = false;
  function P2(x){
    var self = new P(x);
    setProto(self, P2.prototype);
    return self;
  }
  try {
    works = P && P.resolve && testResolve();
    setProto(P2, P);
    P2.prototype = $.create(P.prototype, {constructor: {value: P2}});
    // actual Firefox has broken subclass support, test that
    if(!(P2.resolve(5).then(function(){}) instanceof P2)){
      works = false;
    }
    // actual V8 bug, https://code.google.com/p/v8/issues/detail?id=4162
    if(works && require('./$.support-desc')){
      var thenableThenGotten = false;
      P.resolve($.setDesc({}, 'then', {
        get: function(){ thenableThenGotten = true; }
      }));
      works = thenableThenGotten;
    }
  } catch(e){ works = false; }
  return works;
}();

// helpers
var isPromise = function(it){
  return isObject(it) && (useNative ? classof(it) == 'Promise' : RECORD in it);
};
var sameConstructor = function(a, b){
  // library wrapper special case
  if(LIBRARY && a === P && b === Wrapper)return true;
  return same(a, b);
};
var getConstructor = function(C){
  var S = anObject(C)[SPECIES];
  return S != undefined ? S : C;
};
var isThenable = function(it){
  var then;
  return isObject(it) && typeof (then = it.then) == 'function' ? then : false;
};
var notify = function(record, isReject){
  if(record.n)return;
  record.n = true;
  var chain = record.c;
  asap(function(){
    var value = record.v
      , ok    = record.s == 1
      , i     = 0;
    var run = function(react){
      var cb = ok ? react.ok : react.fail
        , ret, then;
      try {
        if(cb){
          if(!ok)record.h = true;
          ret = cb === true ? value : cb(value);
          if(ret === react.P){
            react.rej(TypeError('Promise-chain cycle'));
          } else if(then = isThenable(ret)){
            then.call(ret, react.res, react.rej);
          } else react.res(ret);
        } else react.rej(value);
      } catch(err){
        react.rej(err);
      }
    };
    while(chain.length > i)run(chain[i++]); // variable length - can't use forEach
    chain.length = 0;
    record.n = false;
    if(isReject)setTimeout(function(){
      asap(function(){
        if(isUnhandled(record.p)){
          if(isNode){
            process.emit('unhandledRejection', value, record.p);
          } else if(global.console && console.error){
            console.error('Unhandled promise rejection', value);
          }
        }
        record.a = undefined;
      });
    }, 1);
  });
};
var isUnhandled = function(promise){
  var record = promise[RECORD]
    , chain  = record.a || record.c
    , i      = 0
    , react;
  if(record.h)return false;
  while(chain.length > i){
    react = chain[i++];
    if(react.fail || !isUnhandled(react.P))return false;
  } return true;
};
var $reject = function(value){
  var record = this;
  if(record.d)return;
  record.d = true;
  record = record.r || record; // unwrap
  record.v = value;
  record.s = 2;
  record.a = record.c.slice();
  notify(record, true);
};
var $resolve = function(value){
  var record = this
    , then;
  if(record.d)return;
  record.d = true;
  record = record.r || record; // unwrap
  try {
    if(then = isThenable(value)){
      asap(function(){
        var wrapper = {r: record, d: false}; // wrap
        try {
          then.call(value, ctx($resolve, wrapper, 1), ctx($reject, wrapper, 1));
        } catch(e){
          $reject.call(wrapper, e);
        }
      });
    } else {
      record.v = value;
      record.s = 1;
      notify(record, false);
    }
  } catch(e){
    $reject.call({r: record, d: false}, e); // wrap
  }
};

// constructor polyfill
if(!useNative){
  // 25.4.3.1 Promise(executor)
  P = function Promise(executor){
    aFunction(executor);
    var record = {
      p: strictNew(this, P, PROMISE),         // <- promise
      c: [],                                  // <- awaiting reactions
      a: undefined,                           // <- checked in isUnhandled reactions
      s: 0,                                   // <- state
      d: false,                               // <- done
      v: undefined,                           // <- value
      h: false,                               // <- handled rejection
      n: false                                // <- notify
    };
    this[RECORD] = record;
    try {
      executor(ctx($resolve, record, 1), ctx($reject, record, 1));
    } catch(err){
      $reject.call(record, err);
    }
  };
  require('./$.mix')(P.prototype, {
    // 25.4.5.3 Promise.prototype.then(onFulfilled, onRejected)
    then: function then(onFulfilled, onRejected){
      var S = anObject(anObject(this).constructor)[SPECIES];
      var react = {
        ok:   typeof onFulfilled == 'function' ? onFulfilled : true,
        fail: typeof onRejected == 'function'  ? onRejected  : false
      };
      var promise = react.P = new (S != undefined ? S : P)(function(res, rej){
        react.res = aFunction(res);
        react.rej = aFunction(rej);
      });
      var record = this[RECORD];
      record.c.push(react);
      if(record.a)record.a.push(react);
      if(record.s)notify(record, false);
      return promise;
    },
    // 25.4.5.1 Promise.prototype.catch(onRejected)
    'catch': function(onRejected){
      return this.then(undefined, onRejected);
    }
  });
}

// export
$def($def.G + $def.W + $def.F * !useNative, {Promise: P});
require('./$.tag')(P, PROMISE);
species(P);
species(Wrapper = require('./$.core')[PROMISE]);

// statics
$def($def.S + $def.F * !useNative, PROMISE, {
  // 25.4.4.5 Promise.reject(r)
  reject: function reject(r){
    return new this(function(res, rej){ rej(r); });
  }
});
$def($def.S + $def.F * (!useNative || testResolve(true)), PROMISE, {
  // 25.4.4.6 Promise.resolve(x)
  resolve: function resolve(x){
    return isPromise(x) && sameConstructor(x.constructor, this)
      ? x : new this(function(res){ res(x); });
  }
});
$def($def.S + $def.F * !(useNative && require('./$.iter-detect')(function(iter){
  P.all(iter)['catch'](function(){});
})), PROMISE, {
  // 25.4.4.1 Promise.all(iterable)
  all: function all(iterable){
    var C      = getConstructor(this)
      , values = [];
    return new C(function(res, rej){
      forOf(iterable, false, values.push, values);
      var remaining = values.length
        , results   = Array(remaining);
      if(remaining)$.each.call(values, function(promise, index){
        C.resolve(promise).then(function(value){
          results[index] = value;
          --remaining || res(results);
        }, rej);
      });
      else res(results);
    });
  },
  // 25.4.4.4 Promise.race(iterable)
  race: function race(iterable){
    var C = getConstructor(this);
    return new C(function(res, rej){
      forOf(iterable, false, function(promise){
        C.resolve(promise).then(res, rej);
      });
    });
  }
});