refactor(serve): add custom parser function for --port option

src/commands/serve/index.test.ts

@@ -116,6 +116,23 @@ describe('serveCommand', () => {
     )
   })
 
+  it('should start server with custom port 0 by allocating a ephemeral port', async () => {
+    mockModules.existsSync.mockReturnValue(false)
+    mockModules.resolve.mockImplementation((cwd: string, path: string) => {
+      return `${cwd}/${path}`
+    })
+
+    await program.parseAsync(['node', 'test', 'serve', '-p', '0'])
+
+    expect(mockServe).toHaveBeenCalledWith(
+      expect.objectContaining({
+        fetch: expect.any(Function),
+        port: 0,
+      }),
+      expect.any(Function)
+    )
+  })
+
   it('should serve app that responds correctly to requests', async () => {
     const mockApp = new Hono()
     mockApp.get('/', (c) => c.text('Hello World'))
@@ -256,4 +273,34 @@ describe('serveCommand', () => {
     expect(unknownResponse.status).toBe(404)
     expect(await unknownResponse.text()).toBe('API endpoint not found')
   })
+
+  describe('port validation', () => {
+    it.each(['-1', '65536', '2048GB', 'invalid'])(
+      'should warn and use default port when port is %s',
+      async (port) => {
+        const consoleWarnSpy = vi.spyOn(console, 'warn').mockImplementation(() => {})
+
+        mockModules.existsSync.mockReturnValue(false)
+        mockModules.resolve.mockImplementation((cwd: string, path: string) => {
+          return `${cwd}/${path}`
+        })
+
+        await program.parseAsync(['node', 'test', 'serve', '-p', port])
+
+        expect(consoleWarnSpy).toHaveBeenCalledWith(
+          'Port must be a number between 0 and 65535. Using default port 7070.\n'
+        )
+
+        expect(mockServe).toHaveBeenCalledWith(
+          expect.objectContaining({
+            fetch: expect.any(Function),
+            port: 7070,
+          }),
+          expect.any(Function)
+        )
+
+        consoleWarnSpy.mockRestore()
+      }
+    )
+  })
 })

src/commands/serve/index.ts

@@ -20,7 +20,14 @@ export function serveCommand(program: Command) {
     .command('serve')
     .description('Start server')
     .argument('[entry]', 'entry file')
-    .option('-p, --port <port>', 'port number')
+    .option('-p, --port <port>', 'port number', (value) => {
+      const parsed = parseInt(value, 10) // 2048GB will be 2048. So we need to check the original value which consists of only digits.
+      if (!/^\d+$/.test(value) || parsed < 0 || parsed > 65535) {
+        console.warn('Port must be a number between 0 and 65535. Using default port 7070.\n')
+        return 7070
+      }
+      return parsed
+    })
     .option('--show-routes', 'show registered routes')
     .option(
       '--use <middleware>',
@@ -33,7 +40,7 @@ export function serveCommand(program: Command) {
     .action(
       async (
         entry: string | undefined,
-        options: { port?: string; showRoutes?: boolean; use?: string[] }
+        options: { port?: number; showRoutes?: boolean; use?: string[] }
       ) => {
         let app: Hono
 
@@ -94,7 +101,7 @@ export function serveCommand(program: Command) {
         serve(
           {
             fetch: baseApp.fetch,
-            port: options.port ? Number.parseInt(options.port) : 7070,
+            port: options.port ?? 7070,
           },
           (info) => {
             console.log(`Listening on http://localhost:${info.port}`)