fix(dev-holocron-cdn): allow no local module map (#433)

__tests__/server/devHolocronCDN.spec.js

@@ -15,7 +15,7 @@
  */
 
 import path from 'path';
-
+import fs from 'fs';
 import findUp from 'find-up';
 import request from 'supertest';
 
@@ -36,6 +36,7 @@ describe('devHolocronCDN', () => {
 
     beforeEach(() => {
       jest.resetModules();
+      jest.spyOn(fs, 'existsSync').mockImplementation(() => true);
       jest.mock('cors', () => jest.fn(() => (req, res, next) => next()));
       jest.mock('@americanexpress/one-app-dev-cdn', () => jest.fn(() => (req, res, next) => next()));
     });
@@ -80,6 +81,27 @@ describe('devHolocronCDN', () => {
           });
         });
     });
+
+    it('does not require useLocalModules when no static module-map', () => {
+      fs.existsSync.mockImplementationOnce(() => false);
+      const moduleMapUrl = 'https://example.com/module-map.json';
+      process.argv = [
+        '',
+        '',
+        '--module-map-url',
+        moduleMapUrl,
+      ];
+
+      load();
+      return findUp('package.json')
+        .then((filepath) => {
+          expect(oneAppDevCdn).toHaveBeenCalledWith({
+            localDevPublicPath: path.join(path.dirname(filepath), 'static'),
+            remoteModuleMapUrl: moduleMapUrl,
+            useLocalModules: false,
+          });
+        });
+    });
   });
 
   describe('routing', () => {

src/server/devHolocronCDN.js

@@ -17,19 +17,21 @@
 /* eslint import/no-extraneous-dependencies: ["error", {"devDependencies": true }] */
 
 import path from 'path';
-
+import fs from 'fs';
 import express from 'express';
 import cors from 'cors';
 import { argv } from 'yargs';
 import oneAppDevCdn from '@americanexpress/one-app-dev-cdn';
 
+const hasLocalModuleMap = () => fs.existsSync(path.join(process.cwd(), 'static', 'module-map.json'));
+
 const app = express();
 
 app.use(cors());
 app.use('/static', oneAppDevCdn({
   localDevPublicPath: path.join(__dirname, '../../static'),
   remoteModuleMapUrl: argv.moduleMapUrl,
-  useLocalModules: true,
+  useLocalModules: hasLocalModuleMap(),
   appPort: process.env.HTTP_PORT,
   useHost: argv.useHost,
 }));