[BUGFIX beta] convert single record sideloaded records to plural

Before, `_normalizeArray` would call `forEach` even if the object wasn't
an array. We guard against it by using `Ember.makeArray`.

fixes #3805

#3805

addon/serializers/rest.js

@@ -187,7 +187,7 @@ var RESTSerializer = JSONSerializer.extend({
     let serializer = store.serializerFor(modelName);
 
     /*jshint loopfunc:true*/
-    arrayHash.forEach((hash) => {
+    Ember.makeArray(arrayHash).forEach((hash) => {
       let { data, included } = this._normalizePolymorphicRecord(store, hash, prop, modelClass, serializer);
       documentHash.data.push(data);
       if (included) {

tests/integration/serializers/rest-serializer-test.js

@@ -23,7 +23,8 @@ module("integration/serializer/rest - RESTSerializer", {
     });
     EvilMinion = DS.Model.extend({
       superVillain: DS.belongsTo('super-villain', { async: false }),
-      name:         DS.attr('string')
+      name:         DS.attr('string'),
+      doomsdayDevice: DS.belongsTo('doomsday-device', {async: false})
     });
     YellowMinion = EvilMinion.extend({
       eyes: DS.attr('number')
@@ -894,3 +895,69 @@ test('Serializer should respect the attrs hash in links', function(assert) {
 
   assert.equal(documentHash.data.relationships.evilMinions.links.related, 'me/minions');
 });
+
+// https://github.com/emberjs/data/issues/3805
+test('normalizes sideloaded single record so that it sideloads correctly - belongsTo - GH-3805', function(assert) {
+  env.registry.register("serializer:doomsday-device", DS.RESTSerializer.extend());
+  let payload = {
+    doomsdayDevice: {
+      id: 1,
+      evilMinion: 2
+    },
+    evilMinion: {
+      id: 2,
+      doomsdayDevice: 1
+    }
+  };
+
+  let document = env.store.serializerFor('doomsday-device').normalizeSingleResponse(env.store, DoomsdayDevice, payload);
+  assert.equal(document.data.relationships.evilMinion.data.id, 2);
+  assert.equal(document.included.length, 1);
+  assert.deepEqual(document.included[0], {
+    attributes: {},
+    id: '2',
+    type: 'evil-minion',
+    relationships: {
+      doomsdayDevice: {
+        data: {
+          id: '1',
+          type: 'doomsday-device'
+        }
+      }
+    }
+  });
+});
+
+// https://github.com/emberjs/data/issues/3805
+test('normalizes sideloaded single record so that it sideloads correctly - hasMany - GH-3805', function(assert) {
+  env.registry.register("serializer:home-planet", DS.RESTSerializer.extend());
+  let payload = {
+    homePlanet: {
+      id: 1,
+      superVillains: [2],
+    },
+    superVillain: {
+      id: 2,
+      homePlanet: 1
+    }
+  };
+
+  let document = env.store.serializerFor('home-planet').normalizeSingleResponse(env.store, HomePlanet, payload);
+
+  assert.equal(document.data.relationships.superVillains.data.length, 1);
+  assert.equal(document.data.relationships.superVillains.data[0].id, 2);
+  assert.equal(document.included.length, 1);
+  assert.deepEqual(document.included[0], {
+    attributes: {},
+    id: '2',
+    type: 'super-villain',
+    relationships: {
+      homePlanet: {
+        data: {
+          id: '1',
+          type: 'home-planet'
+        }
+      }
+    }
+  });
+});