Merge pull request #4292 from Noodlex/fix_model_event_changeId

Trigger the "changeId" event only if prevId is different from this.id.

backbone.js

@@ -523,7 +523,9 @@
       if (this.idAttribute in attrs) {
         var prevId = this.id;
         this.id = this.get(this.idAttribute);
-        this.trigger('changeId', this, prevId, options);
+        if (this.id !== prevId) {
+          this.trigger('changeId', this, prevId, options);
+        }
       }
 
       // Trigger all relevant attribute changes.

test/model.js

@@ -1476,4 +1476,15 @@
     assert.equal(model.id, 3);
   });
 
+  QUnit.test('#4289 - Trigger "changeId" need to be generate only if the content id change', function(assert) {
+    assert.expect(1);
+    var model = new Backbone.Model({id: 1});
+    model.idAttribute = 'id';
+    model.on('changeId', function(m) {
+      assert.equal(m.get('id'), 2);
+    });
+    model.set({id: 1});
+    model.set({id: 2});
+  });
+
 })(QUnit);