perf(nuxt): preload app manifest (#30017)

packages/nuxt/src/app/composables/manifest.ts

@@ -1,7 +1,7 @@
 import type { MatcherExport, RouteMatcher } from 'radix3'
 import { createMatcherFromExport, createRouter as createRadixRouter, toRouteMatcher } from 'radix3'
 import { defu } from 'defu'
-import { useRuntimeConfig } from '../nuxt'
+import { useNuxtApp, useRuntimeConfig } from '../nuxt'
 // @ts-expect-error virtual file
 import { appManifest as isAppManifestEnabled } from '#build/nuxt.config.mjs'
 // @ts-expect-error virtual file
@@ -24,9 +24,14 @@ function fetchManifest () {
   if (!isAppManifestEnabled) {
     throw new Error('[nuxt] app manifest should be enabled with `experimental.appManifest`')
   }
-  manifest = $fetch<NuxtAppManifest>(buildAssetsURL(`builds/meta/${useRuntimeConfig().app.buildId}.json`), {
+  if (import.meta.server) {
-    responseType: 'json',
+    // @ts-expect-error virtual file
-  })
+    manifest = import('#app-manifest')
+  } else {
+    manifest = $fetch<NuxtAppManifest>(buildAssetsURL(`builds/meta/${useRuntimeConfig().app.buildId}.json`), {
+      responseType: 'json',
+    })
+  }
   manifest.then((m) => {
     matcher = createMatcherFromExport(m.matcher)
   }).catch((e) => {
@@ -40,12 +45,16 @@ export function getAppManifest (): Promise<NuxtAppManifest> {
   if (!isAppManifestEnabled) {
     throw new Error('[nuxt] app manifest should be enabled with `experimental.appManifest`')
   }
+  if (import.meta.server) {
+    useNuxtApp().ssrContext!._preloadManifest = true
+  }
   return manifest || fetchManifest()
 }
 
 /** @since 3.7.4 */
 export async function getRouteRules (url: string) {
   if (import.meta.server) {
+    useNuxtApp().ssrContext!._preloadManifest = true
     const _routeRulesMatcher = toRouteMatcher(
       createRadixRouter({ routes: useRuntimeConfig().nitro!.routeRules }),
     )

packages/nuxt/src/app/composables/payload.ts

@@ -85,15 +85,18 @@ async function _importPayload (payloadURL: string) {
 }
 /** @since 3.0.0 */
 export async function isPrerendered (url = useRoute().path) {
+  const nuxtApp = useNuxtApp()
   // Note: Alternative for server is checking x-nitro-prerender header
-  if (!appManifest) { return !!useNuxtApp().payload.prerenderedAt }
+  if (!appManifest) { return !!nuxtApp.payload.prerenderedAt }
   url = withoutTrailingSlash(url)
   const manifest = await getAppManifest()
   if (manifest.prerendered.includes(url)) {
     return true
   }
-  const rules = await getRouteRules(url)
+  return nuxtApp.runWithContext(async () => {
-  return !!rules.prerender && !rules.redirect
+    const rules = await getRouteRules(url)
+    return !!rules.prerender && !rules.redirect
+  })
 }
 
 let payloadCache: NuxtPayload | null = null

packages/nuxt/src/app/nuxt.ts

@@ -83,6 +83,8 @@ export interface NuxtSSRContext extends SSRContext {
     get<T = unknown> (key: string): Promise<T> | undefined
     set<T> (key: string, value: Promise<T>): Promise<void>
   }
+  /** @internal */
+  _preloadManifest?: boolean
 }
 
 export interface NuxtPayload {

packages/nuxt/src/core/nitro.ts

@@ -264,7 +264,18 @@ export async function initNitro (nuxt: Nuxt & { _nitro?: Nitro }) {
 
     nuxt.options.alias['#app-manifest'] = join(tempDir, `meta/${buildId}.json`)
 
+    // write stub manifest before build so external import of #app-manifest can be resolved
+    if (!nuxt.options.dev) {
+      nuxt.hook('build:before', async () => {
+        await fsp.mkdir(join(tempDir, 'meta'), { recursive: true })
+        await fsp.writeFile(join(tempDir, `meta/${buildId}.json`), JSON.stringify({}))
+      })
+    }
+
     nuxt.hook('nitro:config', (config) => {
+      config.alias ||= {}
+      config.alias['#app-manifest'] = join(tempDir, `meta/${buildId}.json`)
+
       const rules = config.routeRules
       for (const rule in rules) {
         if (!(rules[rule] as any).appMiddleware) { continue }
@@ -340,6 +351,11 @@ export async function initNitro (nuxt: Nuxt & { _nitro?: Nitro }) {
     })
   }
 
+  // add stub alias to allow vite to resolve import
+  if (!nuxt.options.experimental.appManifest) {
+    nuxt.options.alias['#app-manifest'] = 'unenv/runtime/mock/proxy'
+  }
+
   // Add fallback server for `ssr: false`
   const FORWARD_SLASH_RE = /\//g
   if (!nuxt.options.ssr) {

packages/nuxt/src/core/runtime/nitro/renderer.ts

@@ -31,7 +31,7 @@ import { renderSSRHeadOptions } from '#internal/unhead.config.mjs'
 
 import type { NuxtPayload, NuxtSSRContext } from '#app'
 // @ts-expect-error virtual file
-import { appHead, appId, appRootAttrs, appRootTag, appTeleportAttrs, appTeleportTag, componentIslands, multiApp } from '#internal/nuxt.config.mjs'
+import { appHead, appId, appRootAttrs, appRootTag, appTeleportAttrs, appTeleportTag, componentIslands, appManifest as isAppManifestEnabled, multiApp } from '#internal/nuxt.config.mjs'
 // @ts-expect-error virtual file
 import { buildAssetsURL, publicAssetsURL } from '#internal/nuxt/paths'
 
@@ -380,7 +380,7 @@ export default defineRenderHandler(async (event): Promise<Partial<RenderResponse
 
   // Setup head
   const { styles, scripts } = getRequestDependencies(ssrContext, renderer.rendererContext)
-  // 1.Extracted payload preloading
+  // 1. Preload payloads and app manifest
   if (_PAYLOAD_EXTRACTION && !NO_SCRIPTS && !isRenderingIsland) {
     head.push({
       link: [
@@ -390,7 +390,13 @@ export default defineRenderHandler(async (event): Promise<Partial<RenderResponse
       ],
     }, headEntryOptions)
   }
-
+  if (isAppManifestEnabled && ssrContext._preloadManifest) {
+    head.push({
+      link: [
+        { rel: 'preload', as: 'fetch', fetchpriority: 'low', crossorigin: 'anonymous', href: buildAssetsURL(`builds/meta/${ssrContext.runtimeConfig.app.buildId}.json`) },
+      ],
+    }, { ...headEntryOptions, tagPriority: 'low' })
+  }
   // 2. Styles
   if (inlinedStyles.length) {
     head.push({ style: inlinedStyles })

packages/vite/src/server.ts

@@ -85,6 +85,7 @@ export async function buildServer (ctx: ViteBuildContext) {
         external: [
           '#internal/nitro',
           '#internal/nuxt/paths',
+          '#app-manifest',
           '#shared',
           new RegExp('^' + escapeStringRegexp(withTrailingSlash(resolve(ctx.nuxt.options.rootDir, ctx.nuxt.options.dir.shared)))),
         ],

packages/webpack/src/configs/server.ts

@@ -59,7 +59,7 @@ function serverStandalone (ctx: WebpackConfigContext) {
     resolve(ctx.nuxt.options.rootDir, ctx.nuxt.options.dir.shared),
   ]
   if (!ctx.nuxt.options.dev) {
-    external.push('#internal/nuxt/paths')
+    external.push('#internal/nuxt/paths', '#app-manifest')
   }
 
   if (!Array.isArray(ctx.config.externals)) { return }