add deferred request to models or collections for race condutions

backbone.js

@@ -215,6 +215,12 @@
  // began.
  _pending: null,
 
+ // Deferred request is a request that is waiting for
+ // response of currently running model request. 
+ // Initial value is false which means 
+ // there is not an currently running request.
+ _deferredRequest: false,
+
  // The default name for the JSON `id` attribute is `"id"`. MongoDB and
  // CouchDB users may want to set this to `"_id"`.
  idAttribute: 'id',
@@ -546,7 +552,6 @@
  }
  return false;
  }
-
  });
 
  // Backbone.Collection
@@ -570,7 +575,13 @@
  // The default model for a collection is just a **Backbone.Model**.
  // This should be overridden in most cases.
  model: Model,
-
+
+ // Deferred request is a request that is waiting for
+ // response of currently running collection request. 
+ // Initial value is false which means 
+ // there is not an currently running request.
+ _deferredRequest: false,
+
  // Initialize is an empty function by default. Override it with your own
  // initialization logic.
  initialize: function(){},
@@ -1345,6 +1356,7 @@
  // Useful when interfacing with server-side languages like **PHP** that make
  // it difficult to read the body of `PUT` requests.
  Backbone.sync = function(method, model, options) {
+
  var type = methodMap[method];
 
  // Default options, unless specified.
@@ -1387,6 +1399,33 @@
  params.processData = false;
  }
 
+ var success = options.success;
+ options.success = function(){
+ var dr = model._deferredRequest;
+ // running request responsed, 
+ // there is no need to defer another request now
+ model._deferredRequest = false;
+
+ // if there is a request that deferred until response for this model
+ if (!_.isEmpty(dr)) {
+ model.sync(dr[0], dr[1], dr[2]);
+ }
+ if (success) success(arguments);
+ };
+
+ // if there is a running request
+ if (_.isArray(model._deferredRequest)) {
+ // defer this request until response of running request.
+ // if there is another deferred request,
+ //override previous deferred request
+ model._deferredRequest = [method, model, options];
+ // FIXME: return sth look like xhr
+ return true;
+ }
+
+ // last requests until response will defer 
+ // but now model._deferredRequest is empty array
+ model._deferredRequest = [];
  // Make the request, allowing the user to override any Ajax options.
  return Backbone.ajax(_.extend(params, options));
  };
@@ -1400,6 +1439,7 @@
  Backbone.wrapError = function(onError, originalModel, options) {
  return function(model, resp) {
  resp = model === originalModel ? resp : model;
+ resp._deferredRequest = false;
  if (onError) {
  onError(originalModel, resp, options);
  } else {

test/sync.js

@@ -20,6 +20,7 @@ $(document).ready(function() {
  library = new Library();
  Backbone.ajax = function(obj) {
  lastRequest = obj;
+ obj.success(obj.data);
  };
  library.create(attrs, {wait: false});
  },
@@ -142,6 +143,28 @@ $(document).ready(function() {
  equal(lastRequest.url, '/one/two');
  });
 
+ test("sync: Defer requests until response", 5, function() {
+ Backbone.ajax = function(obj){
+ lastRequest = obj;
+ // not calling obj.success causes running first request forever 
+ };
+ var model = new Backbone.Model({id:'1'});
+ model.url = '/test';
+ // first long running request that is not deferred
+ model.save({deferred:false});
+ // first deferred request
+ model.save({deferred:true, deferralId:1});
+ strictEqual(model._deferredRequest[1].get('deferred'), true);
+ equal(model._deferredRequest[1].get('deferralId'), 1);
+ // second request that override first deferred request
+ model.save({deferred:true, deferralId:2});
+ equal(model._deferredRequest[1].get('deferralId'), 2);
+ // last deferred request that override previous deferred requests
+ model.destroy();
+ equal(model._deferredRequest[0], 'delete');
+ equal(model._deferredRequest[1].get('deferralId'), 2);
+ });
+
  test("#1052 - `options` is optional.", 0, function() {
  var model = new Backbone.Model();
  model.url = '/test';
@@ -156,5 +179,4 @@ $(document).ready(function() {
  model.url = '/test';
  Backbone.sync('create', model);
  });
-
 });