fix(realtime): open no socket after a logout, and reconnect as soon as the network is back

A connect still waiting for its ws token when the user logged out went on
to open a socket authenticated as that user, which the next login on the
same browser then reused. And a socket in its reconnect backoff waited up
to 30 s after the network came back or the tab became visible. Both
events now reconnect right away.

client/src/api/websocket.extra.test.ts

@@ -1,13 +1,13 @@
 // vi.unmock must run before the module is imported (tests/setup.ts mocks it globally)
 vi.unmock('./websocket')
 
-// FE-WSCORE-001 to FE-WSCORE-014
+// FE-WSCORE-001 to FE-WSCORE-016
 import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
 import { http, HttpResponse } from 'msw'
 import { server } from '../../tests/helpers/msw/server'
 import {
   connect, disconnect, joinTrip, leaveTrip, getActiveTrips,
-  setRefetchCallback, setPreReconnectHook,
+  setRefetchCallback, setPreReconnectHook, reconnectNow,
 } from './websocket'
 
 class MockWebSocket {
@@ -265,3 +265,34 @@ describe('websocket > connection lifecycle', () => {
     expect(MockWebSocket.instances).toHaveLength(2)
   })
 })
+
+describe('websocket > logout and reconnect', () => {
+  it('FE-WSCORE-015: a logout while the token is on its way opens no socket afterwards', async () => {
+    server.use(http.post('/api/auth/ws-token', async () => {
+      await new Promise((r) => setTimeout(r, 50))
+      return HttpResponse.json({ token: 'previous-user' })
+    }))
+    connect()
+    disconnect()
+    await vi.advanceTimersByTimeAsync(100)
+    expect(MockWebSocket.instances).toHaveLength(0)
+  })
+
+  it('FE-WSCORE-016: reconnectNow skips the backoff, and does nothing while logged out or connected', async () => {
+    reconnectNow()
+    await vi.advanceTimersByTimeAsync(0)
+    expect(MockWebSocket.instances).toHaveLength(0)
+
+    const first = await openSocket()
+    reconnectNow()
+    await vi.advanceTimersByTimeAsync(0)
+    expect(MockWebSocket.instances).toHaveLength(1)
+
+    first.readyState = MockWebSocket.CLOSED
+    first.onclose?.()
+    reconnectNow()
+    await vi.advanceTimersByTimeAsync(0)
+    expect(MockWebSocket.instances).toHaveLength(2)
+  })
+})
+

client/src/api/websocket.ts

@@ -22,6 +22,9 @@ let shouldReconnect = false
 let refetchCallback: RefetchCallback | null = null
 let mySocketId: string | null = null
 let connecting = false
+// Bumped by disconnect(): a connect that was still waiting for its token when
+// the user logged out must not open a socket afterwards.
+let generation = 0
 /** Hook run before refetchCallback on reconnect. Awaited so mutations land first. */
 let preReconnectHook: (() => Promise<void>) | null = null
 
@@ -106,8 +109,12 @@ async function connectInternal(_isReconnect = false): Promise<void> {
   }
 
   connecting = true
+  const started = generation
   const wsToken = await fetchWsToken()
   connecting = false
+  // Logged out while the token was on its way: opening now would leave a socket
+  // authenticated as the previous user, which the next login would reuse.
+  if (started !== generation || !shouldReconnect) return
 
   if (!wsToken) {
     if (shouldReconnect) scheduleReconnect()
@@ -163,6 +170,17 @@ async function connectInternal(_isReconnect = false): Promise<void> {
   }
 }
 
+/**
+ * The network came back or the tab became visible: a socket waiting out its
+ * backoff (up to 30 s) reconnects now. Does nothing while logged out or while
+ * a socket is open or opening.
+ */
+export function reconnectNow(): void {
+  if (!shouldReconnect) return
+  if (socket && (socket.readyState === WebSocket.OPEN || socket.readyState === WebSocket.CONNECTING)) return
+  connect()
+}
+
 export function connect(): void {
   shouldReconnect = true
   reconnectDelay = 1000
@@ -175,6 +193,7 @@ export function connect(): void {
 
 export function disconnect(): void {
   shouldReconnect = false
+  generation++
   if (reconnectTimer) {
     clearTimeout(reconnectTimer)
     reconnectTimer = null