Refactor transport factory from object to function

Author: douglascayers

src/core/Ros.ts

@@ -59,7 +59,7 @@ export default class Ros extends EventEmitter<
 
   constructor({
     url,
-    transportFactory = new WebSocketTransportFactory(),
+    transportFactory = WebSocketTransportFactory,
   }: {
     /**
      * The rosbridge server URL. Can be specified later with `connect`.
@@ -91,7 +91,7 @@ export default class Ros extends EventEmitter<
       return; // Already connected
     }
 
-    const transport = await this.transportFactory.createTransport(url);
+    const transport = await this.transportFactory(url);
     this.transport = transport;
 
     transport.on("open", (event: TransportEvent) => {

src/core/Transport.ts

@@ -39,9 +39,7 @@ export interface ITransport {
   isClosed(): boolean;
 }
 
-export interface ITransportFactory {
-  createTransport(url: string): Promise<ITransport>;
-}
+export type ITransportFactory = (url: string) => Promise<ITransport>;
 
 export abstract class AbstractTransport
   extends EventEmitter<{
@@ -363,19 +361,19 @@ export class WsWebSocketTransport extends AbstractTransport {
  * @see https://developer.mozilla.org/en-US/docs/Web/API/WebSocket
  * @see https://github.com/websockets/ws
  */
-export class WebSocketTransportFactory implements ITransportFactory {
-  public async createTransport(url: string): Promise<ITransport> {
-    // Browsers, Deno, Bun, and Node 22+ support WebSockets natively
-    if (typeof WebSocket === "function") {
-      const socket = new WebSocket(url);
-      socket.binaryType = "arraybuffer";
-      return new NativeWebSocketTransport(socket);
-    }
-
-    // If in Node.js, import ws to replace WebSocket API
-    const ws = await import("ws");
-    const socket = new ws.WebSocket(url);
+export const WebSocketTransportFactory: ITransportFactory = async (
+  url: string,
+): Promise<ITransport> => {
+  // Browsers, Deno, Bun, and Node 22+ support WebSockets natively
+  if (typeof WebSocket === "function") {
+    const socket = new WebSocket(url);
     socket.binaryType = "arraybuffer";
-    return new WsWebSocketTransport(socket);
+    return new NativeWebSocketTransport(socket);
   }
-}
+
+  // If in Node.js, import ws to replace WebSocket API
+  const ws = await import("ws");
+  const socket = new ws.WebSocket(url);
+  socket.binaryType = "arraybuffer";
+  return new WsWebSocketTransport(socket);
+};

test/ros.test.ts

@@ -98,9 +98,7 @@ describe("Ros", function () {
       isClosed: vi.fn(),
     };
 
-    mockTransportFactory = {
-      createTransport: vi.fn().mockReturnValue(mockTransport),
-    };
+    mockTransportFactory = vi.fn().mockReturnValue(mockTransport);
   });
 
   afterEach(() => {
@@ -113,7 +111,7 @@ describe("Ros", function () {
       const ros = new Ros();
 
       // @ts-expect-error -- spying on private property
-      expect(ros.transportFactory).toBeInstanceOf(WebSocketTransportFactory);
+      expect(ros.transportFactory).toBe(WebSocketTransportFactory);
     });
 
     it("creates a transport using a factory function", async () => {
@@ -123,9 +121,7 @@ describe("Ros", function () {
 
       await ros.connect(mockRosUrl);
 
-      expect(mockTransportFactory.createTransport).toHaveBeenCalledWith(
-        mockRosUrl,
-      );
+      expect(mockTransportFactory).toHaveBeenCalledWith(mockRosUrl);
     });
 
     it("does not create a new transport if the socket is not closed", async () => {
@@ -135,13 +131,13 @@ describe("Ros", function () {
 
       // always creates a new transport the first time
       await ros.connect(mockRosUrl);
-      expect(mockTransportFactory.createTransport).toHaveBeenCalledTimes(1);
+      expect(mockTransportFactory).toHaveBeenCalledTimes(1);
 
       vi.clearAllMocks();
 
       // socket is not closed so no new transport is created
       await ros.connect(mockRosUrl);
-      expect(mockTransportFactory.createTransport).toHaveBeenCalledTimes(0);
+      expect(mockTransportFactory).toHaveBeenCalledTimes(0);
     });
 
     it("creates a new transport if the socket is closed", async () => {
@@ -151,15 +147,15 @@ describe("Ros", function () {
 
       // always creates a new transport the first time
       await ros.connect(mockRosUrl);
-      expect(mockTransportFactory.createTransport).toHaveBeenCalledTimes(1);
+      expect(mockTransportFactory).toHaveBeenCalledTimes(1);
 
       vi.clearAllMocks();
 
       mockTransport.close();
 
       // socket is closed so a new transport is created
       await ros.connect(mockRosUrl);
-      expect(mockTransportFactory.createTransport).toHaveBeenCalledTimes(1);
+      expect(mockTransportFactory).toHaveBeenCalledTimes(1);
     });
   });
 

test/transport.test.ts

@@ -650,9 +650,7 @@ describe("Transport", () => {
       vi.stubGlobal("WebSocket", WebSocket);
       expect(typeof WebSocket).toBe("function");
 
-      const factory = new WebSocketTransportFactory();
-
-      const transport = await factory.createTransport("ws://localhost:9090");
+      const transport = await WebSocketTransportFactory("ws://localhost:9090");
 
       expect(transport).toBeInstanceOf(NativeWebSocketTransport);
     });
@@ -661,9 +659,7 @@ describe("Transport", () => {
       vi.stubGlobal("WebSocket", undefined);
       expect(typeof WebSocket).toBe("undefined");
 
-      const factory = new WebSocketTransportFactory();
-
-      const transport = await factory.createTransport("ws://localhost:9090");
+      const transport = await WebSocketTransportFactory("ws://localhost:9090");
 
       expect(transport).toBeInstanceOf(WsWebSocketTransport);
     });