fix(nuxt): respect router.options when hmring routes (#30455)

packages/nuxt/src/pages/build.d.ts

@@ -5,3 +5,13 @@ declare module '#build/router.options' {
   const _default: RouterOptions
   export default _default
 }
+
+declare module '#build/routes' {
+  import type { RouterOptions } from '@nuxt/schema'
+  import type { Router, RouterOptions as VueRouterOptions } from 'vue-router'
+
+  export const handleHotUpdate: (_router: Router, _generateRoutes: RouterOptions['routes']) => void
+
+  const _default: VueRouterOptions['routes']
+  export default _default
+}

packages/nuxt/src/pages/module.ts

@@ -621,22 +621,32 @@ const ROUTES_HMR_CODE = /* js */`
 if (import.meta.hot) {
   import.meta.hot.accept((mod) => {
     const router = import.meta.hot.data.router
-    if (!router) {
+    const generateRoutes = import.meta.hot.data.generateRoutes
+    if (!router || !generateRoutes) {
       import.meta.hot.invalidate('[nuxt] Cannot replace routes because there is no active router. Reloading.')
       return
     }
     router.clearRoutes()
-    for (const route of mod.default || mod) {
-      router.addRoute(route)
+    const routes = generateRoutes(mod.default || mod)
+    function addRoutes (routes) {
+      for (const route of routes) {
+        router.addRoute(route)
+      }
+      router.replace('')
+    }
+    if (routes && 'then' in routes) {
+      routes.then(addRoutes)
+    } else {
+      addRoutes(routes)
     }
-    router.replace('')
   })
 }
 
-export function handleHotUpdate(_router) {
+export function handleHotUpdate(_router, _generateRoutes) {
   if (import.meta.hot) {
     import.meta.hot.data ||= {}
     import.meta.hot.data.router = _router
+    import.meta.hot.data.generateRoutes = _generateRoutes
   }
 }
 `

packages/nuxt/src/pages/runtime/plugins/prerender.server.ts

@@ -5,7 +5,6 @@ import defu from 'defu'
 
 import { defineNuxtPlugin, useRuntimeConfig } from '#app/nuxt'
 import { prerenderRoutes } from '#app/composables/ssr'
-// @ts-expect-error virtual file
 import _routes from '#build/routes'
 import routerOptions, { hashMode } from '#build/router.options'
 // @ts-expect-error virtual file
@@ -39,7 +38,7 @@ function shouldPrerender (path: string) {
   return !_routeRulesMatcher || defu({} as Record<string, any>, ..._routeRulesMatcher.matchAll(path).reverse()).prerender
 }
 
-function processRoutes (routes: RouteRecordRaw[], currentPath = '/', routesToPrerender = new Set<string>()) {
+function processRoutes (routes: readonly RouteRecordRaw[], currentPath = '/', routesToPrerender = new Set<string>()) {
   for (const route of routes) {
     // Add root of optional dynamic paths and catchalls
     if (OPTIONAL_PARAM_RE.test(route.path) && !route.children?.length && shouldPrerender(currentPath)) {

packages/nuxt/src/pages/runtime/plugins/router.ts

@@ -17,7 +17,6 @@ import { navigateTo } from '#app/composables/router'
 
 // @ts-expect-error virtual file
 import { appManifest as isAppManifestEnabled } from '#build/nuxt.config.mjs'
-// @ts-expect-error virtual file
 import _routes, { handleHotUpdate } from '#build/routes'
 import routerOptions, { hashMode } from '#build/router.options'
 // @ts-expect-error virtual file
@@ -88,7 +87,7 @@ const plugin: Plugin<{ router: Router }> = defineNuxtPlugin({
       routes,
     })
 
-    handleHotUpdate(router)
+    handleHotUpdate(router, routerOptions.routes ? routerOptions.routes : routes => routes)
 
     if (import.meta.client && 'scrollRestoration' in window.history) {
       window.history.scrollRestoration = 'auto'