fix(server): preserve random port when restarting (#5793)

packages/server/src/listener.js

@@ -5,6 +5,8 @@ import ip from 'ip'
 import consola from 'consola'
 import pify from 'pify'
 
+let RANDOM_PORT = '0'
+
 export default class Listener {
   constructor({ port, host, socket, https, app, dev, baseURL }) {
     // Options
@@ -90,7 +92,7 @@ export default class Listener {
     this.listening = true
   }
 
-  serverErrorHandler(error) {
+  async serverErrorHandler(error) {
     // Detect if port is not available
     const addressInUse = error.code === 'EADDRINUSE'
 
@@ -100,11 +102,14 @@ export default class Listener {
       error.message = `Address \`${address}\` is already in use.`
 
       // Listen to a random port on dev as a fallback
-      if (this.dev && !this.socket && this.port !== '0') {
+      if (this.dev && !this.socket && this.port !== RANDOM_PORT) {
         consola.warn(error.message)
         consola.info('Trying a random port...')
-        this.port = '0'
-        return this.close().then(() => this.listen())
+        this.port = RANDOM_PORT
+        await this.close()
+        await this.listen()
+        RANDOM_PORT = this.port
+        return
       }
     }
 

packages/server/test/listener.test.js

@@ -319,7 +319,7 @@ describe('server: listener', () => {
     const listener = new Listener({})
 
     const error = new Error('server error')
-    expect(() => listener.serverErrorHandler(error)).toThrow(error)
+    expect(listener.serverErrorHandler(error)).rejects.toThrow(error)
   })
 
   test('should throw address in use error', () => {
@@ -329,7 +329,7 @@ describe('server: listener', () => {
 
     const addressInUse = new Error()
     addressInUse.code = 'EADDRINUSE'
-    expect(() => listener.serverErrorHandler(addressInUse)).toThrow('Address `localhost:3000` is already in use.')
+    expect(listener.serverErrorHandler(addressInUse)).rejects.toThrow('Address `localhost:3000` is already in use.')
   })
 
   test('should throw address in use error for socket', () => {
@@ -338,7 +338,7 @@ describe('server: listener', () => {
 
     const addressInUse = new Error()
     addressInUse.code = 'EADDRINUSE'
-    expect(() => listener.serverErrorHandler(addressInUse)).toThrow('Address `nuxt.socket` is already in use.')
+    expect(listener.serverErrorHandler(addressInUse)).rejects.toThrow('Address `nuxt.socket` is already in use.')
   })
 
   test('should fallback to a random port in address in use error', async () => {
@@ -362,6 +362,28 @@ describe('server: listener', () => {
     expect(listener.listen).toBeCalledTimes(1)
   })
 
+  test('should reuse last random port', async () => {
+    const listener = new Listener({ dev: true, host: 'localhost', port: 3000 })
+    listener.host = 'localhost'
+    listener.close = jest.fn()
+    listener.listen = function () {
+      if (this.port === '0') {
+        this.port = Math.random()
+      }
+    }
+
+    const addressInUse = new Error()
+    addressInUse.code = 'EADDRINUSE'
+
+    await listener.serverErrorHandler(addressInUse).catch(() => { })
+    const port1 = listener.port
+    await listener.serverErrorHandler(addressInUse).catch(() => { })
+    const port2 = listener.port
+
+    expect(port1).not.toBe(3000)
+    expect(port2).toBe(port1)
+  })
+
   test('should close server', async () => {
     const listener = new Listener({})
     const server = mockServer()