Convert app-context-init to typescript and fix server.go

Typescript doesn't add .js extension to the imported file name. As a
result, the browser imports the same file twice with different names:
for example app-context and app-context.js. After the fix, server.go
patches the typescript output and adds .js extension. Rollup handles
such cases correctly.

Change-Id: I3290f9244bb6d6dd8547fbceed8ed57186c6f638

polygerrit-ui/app/services/app-context-init.ts

@@ -14,17 +14,24 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-import {appContext} from './app-context.js';
-import {FlagsServiceImplementation} from './flags/flags_impl.js';
-import {GrReporting} from './gr-reporting/gr-reporting_impl.js';
-import {EventEmitter} from './gr-event-interface/gr-event-interface_impl.js';
-import {Auth} from './gr-auth/gr-auth_impl.js';
+import {appContext, AppContext} from './app-context';
+import {FlagsServiceImplementation} from './flags/flags_impl';
+import {GrReporting} from './gr-reporting/gr-reporting_impl';
+import {EventEmitter} from './gr-event-interface/gr-event-interface_impl';
+import {Auth} from './gr-auth/gr-auth_impl';
 
-const initializedServices = new Map();
+type ServiceName = keyof AppContext;
+type ServiceCreator<T> = () => T;
 
-function getService(serviceName, serviceInit) {
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+const initializedServices: Map<ServiceName, any> = new Map();
+
+function getService<K extends ServiceName>(
+  serviceName: K,
+  serviceCreator: ServiceCreator<AppContext[K]>
+): AppContext[K] {
   if (!initializedServices.has(serviceName)) {
-    initializedServices.set(serviceName, serviceInit());
+    initializedServices.set(serviceName, serviceCreator());
   }
   return initializedServices.get(serviceName);
 }
@@ -33,23 +40,30 @@ function getService(serviceName, serviceInit) {
  * The AppContext lazy initializator for all services
  */
 export function initAppContext() {
-  const registeredServices = {};
-  function addService(serviceName, serviceCreator) {
-    if (registeredServices[serviceName]) {
-      throw new Error(`Service ${serviceName} already registered.`);
-    }
-    registeredServices[serviceName] = {
-      configurable: true, // Tests can mock properties
-      get() {
-        return getService(serviceName, serviceCreator);
+  function populateAppContext(
+    serviceCreators: {[P in ServiceName]: ServiceCreator<AppContext[P]>}
+  ) {
+    const registeredServices = Object.keys(serviceCreators).reduce(
+      (registeredServices, key) => {
+        const serviceName = key as ServiceName;
+        const serviceCreator = serviceCreators[serviceName];
+        registeredServices[serviceName] = {
+          configurable: true, // Tests can mock properties
+          get() {
+            return getService(serviceName, serviceCreator);
+          },
+        };
+        return registeredServices;
       },
-    };
+      {} as PropertyDescriptorMap
+    );
+    Object.defineProperties(appContext, registeredServices);
   }
 
-  addService('flagsService', () => new FlagsServiceImplementation());
-  addService('reportingService',
-      () => new GrReporting(appContext.flagsService));
-  addService('eventEmitter', () => new EventEmitter());
-  addService('authService', () => new Auth(appContext.eventEmitter));
-  Object.defineProperties(appContext, registeredServices);
+  populateAppContext({
+    flagsService: () => new FlagsServiceImplementation(),
+    reportingService: () => new GrReporting(appContext.flagsService),
+    eventEmitter: () => new EventEmitter(),
+    authService: () => new Auth(appContext.eventEmitter),
+  });
 }

polygerrit-ui/server.go

@@ -168,17 +168,20 @@ func handleSrcRequest(compiledSrcPath string, dirListingMux *http.ServeMux, writ
 		writer.Header().Set("Content-Type", "text/html")
 	} else if isJsFile {
 	  // The following code updates import statements.
-	  // 1. Keep all imports started with '.' character unchanged (i.e. all relative
-	  // imports like import ... from './a.js' or import ... from '../b/c/d.js'
-	  // 2. For other imports it adds '/node_modules/' prefix. Additionally,
-	  //   if an in imported file has .js or .mjs extension, the code keeps
-	  //   the file extension unchanged. Otherwise, it adds .js extension.
+	  // 1. if an in imported file has .js or .mjs extension, the code keeps
+    //	  the file extension unchanged. Otherwise, it adds .js extension
+	  // 2. For module imports it adds '/node_modules/' prefix.
 	  //   Examples:
 	  //   '@polymer/polymer.js' -> '/node_modules/@polymer/polymer.js'
     //   'page/page.mjs' -> '/node_modules/page.mjs'
     //   '@polymer/iron-icon' -> '/node_modules/@polymer/iron-icon.js'
-		moduleImportRegexp := regexp.MustCompile("(?m)^(import.*)'([^/.].*?)(\\.(m?)js)?';$")
-		data = moduleImportRegexp.ReplaceAll(data, []byte("$1 '/node_modules/$2.${4}js';"))
+    //   './element/file' -> './element/file.js'
+    moduleImportRegexp := regexp.MustCompile("(?m)^(import.*)'(.*?)(\\.(m?)js)?';$")
+    data = moduleImportRegexp.ReplaceAll(data, []byte("$1 '$2.${4}js';"))
+
+		moduleImportRegexp = regexp.MustCompile("(?m)^(import.*)'([^/.].*)';$")
+		data = moduleImportRegexp.ReplaceAll(data, []byte("$1 '/node_modules/$2';"))
+
 		writer.Header().Set("Content-Type", "application/javascript")
 	} else if strings.HasSuffix(normalizedContentPath, ".css") {
 		writer.Header().Set("Content-Type", "text/css")