final steps to ensuring modelClass is unneeded for _push

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

@@ -104,13 +104,12 @@ const {
   @class InternalModel
 */
 export default class InternalModel {
-  constructor(modelClass, id, store, data) {
+  constructor(modelName, id, store, data) {
     heimdall.increment(new_InternalModel);
-    this.modelClass = modelClass;
     this.id = id;
     this.store = store;
     this._data = data || new EmptyObject();
-    this.modelName = modelClass.modelName;
+    this.modelName = modelName;
     this.dataHasInitialized = false;
     this._loadingPromise = null;
     this._recordArrays = undefined;
@@ -122,6 +121,7 @@ export default class InternalModel {
     this.error = null;
 
     // caches for lazy getters
+    this._modelClass = null;
     this.__deferredTriggers = null;
     this._references = null;
     this._recordReference = null;
@@ -131,6 +131,10 @@ export default class InternalModel {
     this.__implicitRelationships = null;
   }
 
+  get modelClass() {
+    return this._modelClass || (this._modelClass = this.store.modelFor(this.modelName));
+  }
+
   get type() {
     return this.modelClass;
   }

addon/-private/system/store.js

@@ -2305,14 +2305,14 @@ Store = Service.extend({
         let unknownAttributes = Object.keys(data.attributes || {}).filter((key) => {
           return !get(modelClass, 'fields').has(key);
         });
-        let unknownAttributesMessage = `The payload for '${modelClass.modelName}' contains these unknown attributes: ${unknownAttributes}. Make sure they've been defined in your model.`;
+        let unknownAttributesMessage = `The payload for '${modelName}' contains these unknown attributes: ${unknownAttributes}. Make sure they've been defined in your model.`;
         warn(unknownAttributesMessage, unknownAttributes.length === 0, { id: 'ds.store.unknown-keys-in-payload' });
 
         // Check unknown relationships
         let unknownRelationships = Object.keys(data.relationships || {}).filter((key) => {
           return !get(modelClass, 'fields').has(key);
         });
-        let unknownRelationshipsMessage = `The payload for '${modelClass.modelName}' contains these unknown relationships: ${unknownRelationships}. Make sure they've been defined in your model.`;
+        let unknownRelationshipsMessage = `The payload for '${modelName}' contains these unknown relationships: ${unknownRelationships}. Make sure they've been defined in your model.`;
         warn(unknownRelationshipsMessage, unknownRelationships.length === 0, { id: 'ds.store.unknown-keys-in-payload' });
       }
     });
@@ -2462,8 +2462,7 @@ Store = Service.extend({
 
     // lookupFactory should really return an object that creates
     // instances with the injections applied
-    // TODO @runspired don't force internalModel to need modelClass up front
-    let internalModel = new InternalModel(recordMap.modelClass, id, this, data);
+    let internalModel = new InternalModel(modelName, id, this, data);
 
     // if we're creating an item, this process will be done
     // later, once the object has been persisted.
@@ -2638,8 +2637,8 @@ function _commit(adapter, store, operation, snapshot) {
   let internalModel = snapshot._internalModel;
   let modelName = snapshot.modelName;
   let modelClass = store.modelFor(modelName);
-  assert(`You tried to update a record but you have no adapter (for ${modelClass.modelName})`, adapter);
-  assert(`You tried to update a record but your adapter (for ${modelClass.modelName}) does not implement '${operation}'`, typeof adapter[operation] === 'function');
+  assert(`You tried to update a record but you have no adapter (for ${modelName})`, adapter);
+  assert(`You tried to update a record but your adapter (for ${modelName}) does not implement '${operation}'`, typeof adapter[operation] === 'function');
   let promise = adapter[operation](store, modelClass, snapshot);
   let serializer = serializerForAdapter(store, adapter, modelName);
   let label = `DS: Extract and notify about ${operation} completion of ${internalModel}`;

tests/unit/store/push-test.js

@@ -731,6 +731,23 @@ test("_push returns an instance of InternalModel if an object is pushed", functi
   assert.notOk(pushResult.record, 'InternalModel is not materialized');
 });
 
+test("_push does not require a modelName to resolve to a modelClass", function(assert) {
+  let originalCall = store.modelFor;
+  store.modelFor = () => { assert.notOk('modelFor was triggered as a result of a call to store._push'); };
+
+  run(function() {
+    store._push({
+      data: {
+        id: 1,
+        type: 'person'
+      }
+    });
+  });
+
+  store.modelFor = originalCall;
+  assert.ok('We made it');
+});
+
 test("_push returns an array of InternalModels if an array is pushed", function(assert) {
   let pushResult;