Deprecate complex objects as an attributes defaultValue.

They often do not work how a user expects.
Closes #3766

.jshintrc

@@ -35,6 +35,7 @@
         "jQuery",
         "expectAssertion",
         "expectDeprecation",
+        "expectNoDeprecation",
         "warns",
         "noWarns",
         "throws",

packages/ember-data/lib/system/model/attributes.js

@@ -226,7 +226,13 @@ function getDefaultValue(record, options, key) {
   if (typeof options.defaultValue === "function") {
     return options.defaultValue.apply(null, arguments);
   } else {
-    return options.defaultValue;
+    let defaultValue = options.defaultValue;
+    Ember.deprecate(`Non primative defaultValues are deprecated because they are shared between all instances. If you would like to use a complex object as a default value please provide a function that returns the complex object.`,
+      typeof defaultValue !== 'object' || defaultValue === null, {
+        id: 'ds.defaultValue.complex-object',
+        until: '3.0.0'
+      });
+    return defaultValue;
   }
 }
 

packages/ember-data/tests/unit/model-test.js

@@ -611,6 +611,41 @@ test("a defaultValue function gets the record, options, and key", function() {
   get(tag, 'createdAt');
 });
 
+test("a complex object defaultValue is deprecated ", function() {
+  var Tag = DS.Model.extend({
+    tagInfo: DS.attr({ defaultValue: [] })
+  });
+  var tag;
+
+  var store = createStore({
+    tag: Tag
+  });
+
+  run(function() {
+    tag = store.createRecord('tag');
+  });
+  expectDeprecation(function() {
+    get(tag, 'tagInfo');
+  }, /Non primative defaultValues are deprecated/);
+});
+
+test("a null defaultValue is not deprecated", function() {
+  var Tag = DS.Model.extend({
+    tagInfo: DS.attr({ defaultValue: null })
+  });
+  var tag;
+
+  var store = createStore({
+    tag: Tag
+  });
+
+  run(function() {
+    tag = store.createRecord('tag');
+  });
+  expectNoDeprecation();
+  equal(get(tag, 'tagInfo'), null);
+});
+
 test("setting a property to undefined on a newly created record should not impact the current state", function() {
   var Tag = DS.Model.extend({
     name: DS.attr('string')