fix(ivy): don't load factories when using Ivy (#28685)

Related to https://github.com/angular/angular/pull/26947/files#r251221208
Related to angular/angular-cli#13524

PR Close #28685

packages/core/src/linker/system_js_ng_module_factory_loader.ts

@@ -8,6 +8,7 @@
 
 
 import {Injectable, Optional} from '../di';
+import {ivyEnabled} from '../ivy_switch';
 
 import {Compiler} from './compiler';
 import {NgModuleFactory} from './ng_module_factory';
@@ -56,8 +57,8 @@ export class SystemJsNgModuleLoader implements NgModuleFactoryLoader {
   }
 
   load(path: string): Promise<NgModuleFactory<any>> {
-    const offlineMode = this._compiler instanceof Compiler;
-    return offlineMode ? this.loadFactory(path) : this.loadAndCompile(path);
+    const legacyOfflineMode = !ivyEnabled && this._compiler instanceof Compiler;
+    return legacyOfflineMode ? this.loadFactory(path) : this.loadAndCompile(path);
   }
 
   private loadAndCompile(path: string): Promise<NgModuleFactory<any>> {

packages/core/test/linker/system_ng_module_factory_loader_spec.ts

@@ -10,6 +10,7 @@ import {Compiler, SystemJsNgModuleLoader} from '@angular/core';
 import {global} from '@angular/core/src/util/global';
 import {async} from '@angular/core/testing';
 import {afterEach, beforeEach, describe, expect, it} from '@angular/core/testing/src/testing_internal';
+import {modifiedInIvy, onlyInIvy} from '@angular/private/testing';
 
 function mockSystem(modules: {[module: string]: any}) {
   return {
@@ -20,9 +21,9 @@ function mockSystem(modules: {[module: string]: any}) {
   };
 }
 
-{
-  describe('SystemJsNgModuleLoader', () => {
+describe('SystemJsNgModuleLoader', () => {
   let oldSystem: any = null;
+  modifiedInIvy('only loads ngfactory shims in View Engine').describe('(View Engine)', () => {
     beforeEach(() => {
       oldSystem = global['System'];
       global['System'] = mockSystem({
@@ -54,4 +55,26 @@ function mockSystem(modules: {[module: string]: any}) {
          });
        }));
   });
-}
+
+  onlyInIvy('loads modules directly in Ivy').describe('(Ivy)', () => {
+    beforeEach(() => {
+      oldSystem = global['System'];
+      global['System'] = mockSystem({
+        'test': {'default': 'test module', 'NamedModule': 'test NamedModule'},
+      });
+    });
+    afterEach(() => { global['System'] = oldSystem; });
+
+    it('loads a default module', async(() => {
+         const loader = new SystemJsNgModuleLoader(new Compiler());
+         loader.load('test').then(
+             contents => { expect(contents.moduleType).toBe('test module' as any); });
+       }));
+    it('loads a named module', async(() => {
+         const loader = new SystemJsNgModuleLoader(new Compiler());
+         loader.load('test#NamedModule').then(contents => {
+           expect(contents.moduleType).toBe('test NamedModule' as any);
+         });
+       }));
+  });
+});