[Fixes #4807] realize class + factory seperation

*note: this combined with embers factoryFor makes `MODEL_FACTORY_INJECTIONS` irrelevant.*

addon/-private/system/model/internal-model.js

@@ -330,7 +330,7 @@ export default class InternalModel {
         createOptions.container = this.store.container;
       }
 
-      this._record = this.modelClass._create(createOptions);
+      this._record = this.store.modelFactoryFor(this.modelName).create(createOptions);
 
       this._triggerDeferredTriggers();
       heimdall.stop(token);

addon/-private/system/model/model.js

@@ -10,6 +10,7 @@ import {
   relatedTypesDescriptor,
   relationshipsDescriptor
 } from 'ember-data/-private/system/relationships/ext';
+import { runInDebug } from 'ember-data/-private/debug';
 
 const {
   get,
@@ -21,7 +22,6 @@ const {
   @module ember-data
 */
 
-
 function findPossibleInverses(type, inverseType, name, relationshipsSoFar) {
   let possibleRelationships = relationshipsSoFar || [];
 
@@ -1173,17 +1173,20 @@ Object.defineProperty(Model.prototype, 'data', {
   }
 });
 
-Model.reopenClass({
-  /**
-    Alias DS.Model's `create` method to `_create`. This allows us to create DS.Model
-    instances from within the store, but if end users accidentally call `create()`
-    (instead of `createRecord()`), we can raise an error.
+runInDebug(function() {
+  Model.reopen({
+    init() {
+      this._super(...arguments);
 
-    @method _create
-    @private
-    @static
-  */
-  _create: Model.create,
+      if (!this._internalModel) {
+        throw new Ember.Error('You should not call `create` on a model. Instead, call `store.createRecord` with the attributes you would like to set.');
+      }
+    }
+  });
+});
+
+Model.reopenClass({
+  isModel: true,
 
   /**
     Override the class' `create()` method to raise an error. This
@@ -1196,10 +1199,6 @@ Model.reopenClass({
     @private
     @static
   */
-  create() {
-    throw new Ember.Error("You should not call `create` on a model. Instead, call `store.createRecord` with the attributes you would like to set.");
-  },
-
   /**
    Represents the model's class name as a string. This can be used to look up the model through
    DS.Store's modelFor method.

addon/-private/system/store.js

@@ -2087,6 +2087,12 @@ Store = Service.extend({
     @private
    */
   _modelFor(modelName) {
+    let maybeFactory = this._modelFactoryFor(modelName);
+    // for factorFor factory/class split
+    return maybeFactory.class ? maybeFactory.class : maybeFactory;
+  },
+
+  _modelFactoryFor(modelName) {
     heimdall.increment(modelFor);
     let factory = this._modelClassCache[modelName];
 
@@ -2101,9 +2107,13 @@ Store = Service.extend({
         throw new EmberError(`No model was found for '${modelName}'`);
       }
 
-      assert(`'${inspect(factory)}' does not appear to be an ember-data model`, (typeof factory._create === 'function') );
+      // interopt with the future
+      let klass = getOwner(this).factoryFor ? factory.class : factory;
+
+      assert(`'${inspect(klass)}' does not appear to be an ember-data model`, klass.isModel);
 
-      factory.modelName = factory.modelName || modelName;
+      // TODO: deprecate this
+      klass.modelName = klass.modelName || modelName;
 
       this._modelClassCache[modelName] = factory;
     }
@@ -2116,16 +2126,13 @@ Store = Service.extend({
    */
   modelFactoryFor(modelName) {
     heimdall.increment(modelFactoryFor);
-    assert("You need to pass a model name to the store's modelFactoryFor method", isPresent(modelName));
-    assert('Passing classes to store methods has been removed. Please pass a dasherized string instead of '+ inspect(modelName), typeof modelName === 'string');
+    assert(`You need to pass a model name to the store's modelFactoryFor method`, isPresent(modelName));
+    assert(`Passing classes to store methods has been removed. Please pass a dasherized string instead of ${modelName}`, typeof modelName === 'string');
     let trueModelName = this._classKeyFor(modelName);
     let owner = getOwner(this);
 
     if (owner.factoryFor) {
-      let MaybeModel = owner.factoryFor(`model:${trueModelName}`);
-      let MaybeModelFactory = MaybeModel && MaybeModel.class;
-
-      return MaybeModelFactory;
+      return owner.factoryFor(`model:${trueModelName}`);
     } else {
       return owner._lookupFactory(`model:${trueModelName}`);
     }

tests/integration/injection-test.js

@@ -0,0 +1,76 @@
+import setupStore from 'dummy/tests/helpers/store';
+import Ember from 'ember';
+import DS from 'ember-data';
+import { module, test } from 'qunit';
+
+let env, originalFactoryFor, originalMODEL_FACTORY_INJECTIONS = Ember.MODEL_FACTORY_INJECTIONS;
+const { run } = Ember;
+
+const factory = {
+  isFactory: true,
+  class: {
+    isModel: true,
+    _create() { }
+  }
+};
+
+module('integration/injection factoryFor enabled', {
+  setup() {
+    env = setupStore();
+
+    originalFactoryFor = Ember.getOwner(env.store).factoryFor;
+
+    Ember.getOwner(env.store).factoryFor = function(name) {
+      return factory;
+    };
+  },
+
+  teardown() {
+    Ember.getOwner(env.store).factoryFor = originalFactoryFor;
+
+    run(env.store, 'destroy');
+  }
+});
+
+test('modelFactoryFor', function(assert) {
+  const modelFactory = env.store.modelFactoryFor('super-villain');
+
+  assert.equal(modelFactory, factory, 'expected the factory itself to be returned');
+});
+
+test('modelFor', function(assert) {
+  const modelFactory = env.store.modelFor('super-villain');
+
+  assert.equal(modelFactory, factory.class, 'expected the factory itself to be returned');
+
+  // TODO: we should deprecate this next line. Resolved state on the class is fraught with peril
+  assert.equal(modelFactory.modelName, 'super-villain', 'expected the factory itself to be returned');
+});
+
+module('integration/injection eager injections', {
+  setup() {
+    Ember.MODEL_FACTORY_INJECTIONS = true;
+    env = setupStore();
+
+    env.registry.injection('model:foo', 'apple', 'service:apple');
+    env.registry.register('model:foo',     DS.Model);
+    env.registry.register('service:apple', Ember.Object.extend({ isService: true }));
+    // container injection
+  },
+
+  teardown() {
+    // can be removed once we no longer support ember versions without lookupFactory
+    Ember.MODEL_FACTORY_INJECTIONS = originalMODEL_FACTORY_INJECTIONS;
+
+    run(env.store, 'destroy');
+  }
+});
+
+test('did inject', function(assert) {
+  let foo = run(() => env.store.createRecord('foo'));
+  let apple = foo.get('apple');
+  let Apple = env.registry.registrations['service:apple'];
+
+  assert.ok(apple, `'model:foo' instance should have an 'apple' property`);
+  assert.ok(apple instanceof Apple, `'model:foo'.apple should be an instance of 'service:apple'`);
+});

tests/unit/model-test.js

@@ -15,7 +15,7 @@ var run = Ember.run;
 
 var Person, store, env;
 
-module("unit/model - DS.Model", {
+module('unit/model - DS.Model', {
   beforeEach() {
     Person = DS.Model.extend({
       name: DS.attr('string'),