fix(dev): set hmr server on server.ws (vite 8.1+)

packages/nuxi/src/dev/utils.ts

@@ -1,10 +1,10 @@
-import type { Nuxt, NuxtConfig } from '@nuxt/schema'
+import type { Nuxt, NuxtConfig, ViteConfig } from '@nuxt/schema'
 import type { DotenvOptions } from 'c12'
 import type { Listener, ListenOptions } from 'listhen'
 import type { createDevServer } from 'nitro/builder'
 import type { NitroDevServer } from 'nitropack'
 import type { FSWatcher } from 'node:fs'
-import type { IncomingMessage, RequestListener, ServerResponse } from 'node:http'
+import type { Server as HttpServer, IncomingMessage, RequestListener, ServerResponse } from 'node:http'
 
 import EventEmitter from 'node:events'
 import { existsSync, readdirSync, statSync, watch } from 'node:fs'
@@ -116,6 +116,31 @@ export class FileChangeTracker {
 
 type NuxtWithServer = Omit<Nuxt, 'server'> & { server?: NitroDevServer | ReturnType<typeof createDevServer> }
 
+type ViteServerOptions = NonNullable<ViteConfig['server']>
+type HmrOptions = Exclude<ViteServerOptions['hmr'], boolean>
+
+/**
+ * Pin Vite's HMR websocket to the main dev server so no separate HMR port is allocated.
+ * vite >= 8.1 reads `server.ws`; older versions only read `server.hmr`.
+ */
+export function attachViteHmrServer(server: ViteServerOptions, hmrServer: HttpServer): void {
+  const target = server as Omit<ViteServerOptions, 'ws'> & { ws?: HmrOptions | boolean }
+  target.ws = {
+    protocol: undefined,
+    ...(target.ws as HmrOptions),
+    port: undefined,
+    host: undefined,
+    server: hmrServer,
+  }
+  target.hmr = {
+    protocol: undefined,
+    ...(target.hmr as HmrOptions),
+    port: undefined,
+    host: undefined,
+    server: hmrServer,
+  }
+}
+
 interface DevServerEventMap {
   'loading:error': [error: Error]
   'loading': [loadingMessage: string]
@@ -349,13 +374,7 @@ export class NuxtDevServer extends EventEmitter<DevServerEventMap> {
     if (!process.env.NUXI_DISABLE_VITE_HMR) {
       this.#currentNuxt.hooks.hook('vite:extend', ({ config }) => {
         if (config.server) {
-          config.server.hmr = {
-            protocol: undefined,
-            ...(config.server.hmr as Exclude<typeof config.server.hmr, boolean>),
-            port: undefined,
-            host: undefined,
-            server: this.listener.server,
-          }
+          attachViteHmrServer(config.server, this.listener.server)
         }
       })
     }

packages/nuxi/test/unit/dev-hmr.spec.ts

@@ -0,0 +1,44 @@
+import type { Server } from 'node:http'
+import { describe, expect, it } from 'vitest'
+
+import { attachViteHmrServer } from '../../src/dev/utils'
+
+const hmrServer = {} as Server
+
+describe('attachViteHmrServer', () => {
+  it('pins the dev server on both ws and hmr with no separate port', () => {
+    const server: Record<string, unknown> = {}
+
+    attachViteHmrServer(server, hmrServer)
+
+    for (const key of ['ws', 'hmr'] as const) {
+      expect(server[key]).toMatchObject({
+        protocol: undefined,
+        port: undefined,
+        host: undefined,
+        server: hmrServer,
+      })
+    }
+  })
+
+  it('preserves user-set ws and hmr options other than server/port/host', () => {
+    const server: Record<string, unknown> = {
+      ws: { clientPort: 1234 },
+      hmr: { overlay: false },
+    }
+
+    attachViteHmrServer(server, hmrServer)
+
+    expect(server.ws).toMatchObject({ clientPort: 1234, server: hmrServer, port: undefined, host: undefined })
+    expect(server.hmr).toMatchObject({ overlay: false, server: hmrServer, port: undefined, host: undefined })
+  })
+
+  it('does not crash when ws or hmr is set to false', () => {
+    const server: Record<string, unknown> = { ws: false, hmr: false }
+
+    expect(() => attachViteHmrServer(server, hmrServer)).not.toThrow()
+
+    expect(server.ws).toMatchObject({ server: hmrServer })
+    expect(server.hmr).toMatchObject({ server: hmrServer })
+  })
+})