feat(nuxt): payload rendering support (#6455)

Co-authored-by: Daniel Roe <daniel@roe.dev>

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

@@ -13,3 +13,4 @@ export { useRequestHeaders, useRequestEvent, setResponseStatus } from './ssr'
 export { abortNavigation, addRouteMiddleware, defineNuxtRouteMiddleware, setPageLayout, navigateTo, useRoute, useActiveRoute, useRouter } from './router'
 export type { AddRouteMiddlewareOptions, RouteMiddleware } from './router'
 export { preloadComponents, prefetchComponents } from './preload'
+export { isPrerendered, loadPayload, preloadPayload } from './payload'

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

@@ -0,0 +1,60 @@
+import { parseURL, joinURL } from 'ufo'
+import { useNuxtApp } from '../nuxt'
+import { useHead } from '#app'
+
+interface LoadPayloadOptions {
+  fresh?: boolean
+  hash?: string
+}
+
+export function loadPayload (url: string, opts: LoadPayloadOptions = {}) {
+  if (process.server) { return null }
+  const payloadURL = _getPayloadURL(url, opts)
+  const nuxtApp = useNuxtApp()
+  const cache = nuxtApp._payloadCache = nuxtApp._payloadCache || {}
+  if (cache[payloadURL]) {
+    return cache[payloadURL]
+  }
+  cache[url] = _importPayload(payloadURL).then((payload) => {
+    if (!payload) {
+      delete cache[url]
+      return null
+    }
+    return payload
+  })
+  return cache[url]
+}
+
+export function preloadPayload (url: string, opts: LoadPayloadOptions = {}) {
+  const payloadURL = _getPayloadURL(url, opts)
+  useHead({
+    link: [
+      { rel: 'modulepreload', href: payloadURL }
+    ]
+  })
+}
+
+// --- Internal ---
+
+function _getPayloadURL (url: string, opts: LoadPayloadOptions = {}) {
+  const parsed = parseURL(url)
+  if (parsed.search) {
+    throw new Error('Payload URL cannot contain search params: ' + url)
+  }
+  const hash = opts.hash || (opts.fresh ? Date.now() : '')
+  return joinURL(parsed.pathname, hash ? `_payload.${hash}.js` : '_payload.js')
+}
+
+async function _importPayload (payloadURL: string) {
+  if (process.server) { return null }
+  const res = await import(/* webpackIgnore: true */ /* @vite-ignore */ payloadURL).catch((err) => {
+    console.warn('[nuxt] Cannot load payload ', payloadURL, err)
+  })
+  return res?.default || null
+}
+
+export function isPrerendered () {
+  // Note: Alternative for server is checking x-nitro-prerender header
+  const nuxtApp = useNuxtApp()
+  return !!nuxtApp.payload.prerenderedAt
+}

packages/nuxt/src/app/nuxt.ts

@@ -74,6 +74,7 @@ interface _NuxtApp {
   ssrContext?: NuxtSSRContext
   payload: {
     serverRendered?: boolean
+    prerenderedAt?: number
     data: Record<string, any>
     state: Record<string, any>
     rendered?: Function

packages/nuxt/src/app/plugins/payload.client.ts

@@ -0,0 +1,19 @@
+import { defineNuxtPlugin, loadPayload, addRouteMiddleware, isPrerendered } from '#app'
+
+export default defineNuxtPlugin((nuxtApp) => {
+  // Only enable behavior if initial page is prerendered
+  // TOOD: Support hybrid
+  if (!isPrerendered()) {
+    return
+  }
+  addRouteMiddleware(async (to, from) => {
+    if (to.path === from.path) { return }
+    const url = to.path
+    const payload = await loadPayload(url)
+    if (!payload) {
+      return
+    }
+    Object.assign(nuxtApp.payload.data, payload.data)
+    Object.assign(nuxtApp.payload.state, payload.state)
+  })
+})

packages/nuxt/src/core/nuxt.ts

@@ -1,7 +1,7 @@
 import { join, normalize, resolve } from 'pathe'
 import { createHooks } from 'hookable'
 import type { Nuxt, NuxtOptions, NuxtConfig, ModuleContainer, NuxtHooks } from '@nuxt/schema'
-import { loadNuxtConfig, LoadNuxtOptions, nuxtCtx, installModule, addComponent, addVitePlugin, addWebpackPlugin, tryResolveModule } from '@nuxt/kit'
+import { loadNuxtConfig, LoadNuxtOptions, nuxtCtx, installModule, addComponent, addVitePlugin, addWebpackPlugin, tryResolveModule, addPlugin } from '@nuxt/kit'
 // Temporary until finding better placement
 /* eslint-disable import/no-restricted-paths */
 import escapeRE from 'escape-string-regexp'
@@ -166,6 +166,9 @@ async function initNuxt (nuxt: Nuxt) {
     }
   })
 
+  // Add prerender payload support
+  addPlugin(resolve(nuxt.options.appDir, 'plugins/payload.client'))
+
   for (const m of modulesToInstall) {
     if (Array.isArray(m)) {
       await installModule(m[0], m[1])

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

@@ -1,8 +1,9 @@
 import { createRenderer } from 'vue-bundle-renderer/runtime'
 import type { RenderResponse } from 'nitropack'
 import type { Manifest } from 'vite'
-import { getQuery } from 'h3'
+import { appendHeader, getQuery } from 'h3'
 import devalue from '@nuxt/devalue'
+import { joinURL } from 'ufo'
 import { renderToString as _renderToString } from 'vue/server-renderer'
 import { useRuntimeConfig, useNitroApp, defineRenderHandler } from '#internal/nitro'
 // eslint-disable-next-line import/no-restricted-paths
@@ -102,10 +103,25 @@ const getSPARenderer = lazyCachedFunction(async () => {
   return { renderToString }
 })
 
+const PAYLOAD_CACHE = process.env.prerender ? new Map() : null // TODO: Use LRU cache
+const PAYLOAD_URL_RE = /\/_payload(\.[a-zA-Z0-9]+)?.js(\?.*)?$/
+
 export default defineRenderHandler(async (event) => {
   // Whether we're rendering an error page
-  const ssrError = event.req.url?.startsWith('/__nuxt_error') ? getQuery(event) as Exclude<NuxtApp['payload']['error'], Error> : null
-  const url = ssrError?.url as string || event.req.url!
+  const ssrError = event.req.url?.startsWith('/__nuxt_error')
+    ? getQuery(event) as Exclude<NuxtApp['payload']['error'], Error>
+    : null
+  let url = ssrError?.url as string || event.req.url!
+
+  // Whether we are rendering payload route
+  const isRenderingPayload = PAYLOAD_URL_RE.test(url)
+  if (isRenderingPayload) {
+    url = url.substring(0, url.lastIndexOf('/')) || '/'
+    event.req.url = url
+    if (process.env.prerender && PAYLOAD_CACHE!.has(url)) {
+      return PAYLOAD_CACHE!.get(url)
+    }
+  }
 
   // Initialize ssr context
   const ssrContext: NuxtSSRContext = {
@@ -117,7 +133,13 @@ export default defineRenderHandler(async (event) => {
     noSSR: !!event.req.headers['x-nuxt-no-ssr'],
     error: !!ssrError,
     nuxt: undefined!, /* NuxtApp */
-    payload: ssrError ? { error: ssrError } as NuxtSSRContext['payload'] : undefined!
+    payload: (ssrError ? { error: ssrError } : {}) as NuxtSSRContext['payload']
+  }
+
+  // Whether we are prerendering route
+  const payloadURL = process.env.prerender ? joinURL(url, '_payload.js') : undefined
+  if (process.env.prerender) {
+    ssrContext.payload.prerenderedAt = Date.now()
   }
 
   // Render app
@@ -138,6 +160,22 @@ export default defineRenderHandler(async (event) => {
     throw ssrContext.payload.error
   }
 
+  // Directly render payload routes
+  if (isRenderingPayload) {
+    const response = renderPayloadResponse(ssrContext)
+    if (process.env.prerender) {
+      PAYLOAD_CACHE!.set(url, response)
+    }
+    return response
+  }
+
+  if (process.env.prerender) {
+    // Hint nitro to prerender payload for this route
+    appendHeader(event, 'x-nitro-prerender', payloadURL!)
+    // Use same ssr context to generate payload for this route
+    PAYLOAD_CACHE!.set(url, renderPayloadResponse(ssrContext))
+  }
+
   // Render meta
   const renderedMeta = await ssrContext.renderMeta?.() ?? {}
 
@@ -151,6 +189,7 @@ export default defineRenderHandler(async (event) => {
     htmlAttrs: normalizeChunks([renderedMeta.htmlAttrs]),
     head: normalizeChunks([
       renderedMeta.headTags,
+      !process.env.NUXT_NO_SCRIPTS && process.env.prerender ? `<link rel="modulepreload" href="${payloadURL}">` : null,
       _rendered.renderResourceHints(),
       _rendered.renderStyles(),
       inlinedStyles,
@@ -166,8 +205,13 @@ export default defineRenderHandler(async (event) => {
       _rendered.html
     ],
     bodyAppend: normalizeChunks([
-      process.env.NUXT_NO_SCRIPTS ? '' : `<script>window.__NUXT__=${devalue(ssrContext.payload)}</script>`,
-      process.env.NUXT_NO_SCRIPTS ? '' : _rendered.renderScripts(),
+      process.env.NUXT_NO_SCRIPTS
+        ? undefined
+        : (process.env.prerender
+            ? `<script type="module">import p from "${payloadURL}";window.__NUXT__={...p,...(${devalue(splitPayload(ssrContext).initial)})}</script>`
+            : `<script>window.__NUXT__=${devalue(ssrContext.payload)}</script>`
+          ),
+      _rendered.renderScripts(),
       // Note: bodyScripts may contain tags other than <script>
       renderedMeta.bodyScripts
     ])
@@ -233,3 +277,23 @@ async function renderInlineStyles (usedModules: Set<string> | string[]) {
   }
   return Array.from(inlinedStyles).join('')
 }
+
+function renderPayloadResponse (ssrContext: NuxtSSRContext) {
+  return <RenderResponse> {
+    body: `export default ${devalue(splitPayload(ssrContext).payload)}`,
+    statusCode: ssrContext.event.res.statusCode,
+    statusMessage: ssrContext.event.res.statusMessage,
+    headers: {
+      'content-type': 'text/javascript;charset=UTF-8',
+      'x-powered-by': 'Nuxt'
+    }
+  }
+}
+
+function splitPayload (ssrContext: NuxtSSRContext) {
+  const { data, state, prerenderedAt, ...initial } = ssrContext.payload
+  return {
+    initial: { ...initial, prerenderedAt },
+    payload: { data, state, prerenderedAt }
+  }
+}

packages/nuxt/src/imports/presets.ts

@@ -55,7 +55,10 @@ const appPreset = defineUnimportPreset({
     'updateAppConfig',
     'defineAppConfig',
     'preloadComponents',
-    'prefetchComponents'
+    'prefetchComponents',
+    'loadPayload',
+    'preloadPayload',
+    'isPrerendered'
   ]
 })
 

test/basic.test.ts

@@ -2,7 +2,7 @@ import { fileURLToPath } from 'node:url'
 import { describe, expect, it } from 'vitest'
 import { joinURL } from 'ufo'
 // import { isWindows } from 'std-env'
-import { setup, fetch, $fetch, startServer, createPage } from '@nuxt/test-utils'
+import { setup, fetch, $fetch, startServer, createPage, url } from '@nuxt/test-utils'
 // eslint-disable-next-line import/order
 import { expectNoClientErrors, renderPage } from './utils'
 
@@ -586,6 +586,52 @@ describe('app config', () => {
   })
 })
 
+describe('payload rendering', () => {
+  it('renders a payload', async () => {
+    const payload = await $fetch('/random/a/_payload.js', { responseType: 'text' })
+    expect(payload).toMatch(
+      /export default \{data:\{\$frand_a:\[[^\]]*\]\},state:\{"\$srandom:rand_a":\d*,"\$srandom:default":\d*\},prerenderedAt:\d*\}/
+    )
+  })
+
+  it('does not fetch a prefetched payload', async () => {
+    const page = await createPage()
+    const requests = [] as string[]
+    page.on('request', (req) => {
+      requests.push(req.url().replace(url('/'), '/'))
+    })
+    await page.goto(url('/random/a'))
+    await page.waitForLoadState('networkidle')
+
+    const importSuffix = process.env.NUXT_TEST_DEV && !process.env.TEST_WITH_WEBPACK ? '?import' : ''
+
+    // We are manually prefetching other payloads
+    expect(requests).toContain('/random/c/_payload.js')
+
+    // We are not triggering API requests in the payload
+    expect(requests).not.toContain(expect.stringContaining('/api/random'))
+    requests.length = 0
+
+    await page.click('[href="/random/b"]')
+    await page.waitForLoadState('networkidle')
+    // We are not triggering API requests in the payload in client-side nav
+    expect(requests).not.toContain('/api/random')
+    // We are fetching a payload we did not prefetch
+    expect(requests).toContain('/random/b/_payload.js' + importSuffix)
+    // We are not refetching payloads we've already prefetched
+    expect(requests.filter(p => p.includes('_payload')).length).toBe(1)
+    requests.length = 0
+
+    await page.click('[href="/random/c"]')
+    await page.waitForLoadState('networkidle')
+    // We are not triggering API requests in the payload in client-side nav
+    expect(requests).not.toContain('/api/random')
+    // We are not refetching payloads we've already prefetched
+    // Note: we refetch on dev as urls differ between '' and '?import'
+    expect(requests.filter(p => p.includes('_payload')).length).toBe(process.env.NUXT_TEST_DEV ? 1 : 0)
+  })
+})
+
 describe('useAsyncData', () => {
   it('single request resolves', async () => {
     await expectNoClientErrors('/useAsyncData/single')

test/fixtures/basic/composables/random.ts

@@ -0,0 +1,3 @@
+export function useRandomState (max: number = 100, name = 'default') {
+  return useState('random:' + name, () => Math.round(Math.random() * max))
+}

test/fixtures/basic/nuxt.config.ts

@@ -17,7 +17,14 @@ export default defineNuxtConfig({
     './extends/node_modules/foo'
   ],
   nitro: {
-    output: { dir: process.env.NITRO_OUTPUT_DIR }
+    output: { dir: process.env.NITRO_OUTPUT_DIR },
+    prerender: {
+      routes: [
+        '/random/a',
+        '/random/b',
+        '/random/c'
+      ]
+    }
   },
   publicRuntimeConfig: {
     testConfig: 123

test/fixtures/basic/pages/assets.vue

@@ -13,12 +13,16 @@ import logo from '~/assets/logo.svg'
 <style>
 #__nuxt {
   background-image: url('~/assets/logo.svg');
+  background-repeat: no-repeat;
+  background-position: bottom right;
   @font-face {
     src: url("/public.svg") format("woff2");
   }
 }
 body {
   background-image: url('/public.svg');
+  background-repeat: no-repeat;
+  background-position: top;
   @font-face {
     src: url('/public.svg') format('woff2');
   }

test/fixtures/basic/pages/random/[id].vue

@@ -0,0 +1,47 @@
+<template>
+  <div>
+    <NuxtLink to="/random/a">
+      Random (A)
+    </NuxtLink>
+    <NuxtLink to="/random/b">
+      Random (B)
+    </NuxtLink>
+    <NuxtLink to="/random/c">
+      Random (C)
+    </NuxtLink>
+    <br>
+
+    Random: {{ random }}
+
+    Random: (global) {{ globalRandom }}
+
+    Random page: <b>{{ route.params.id }}</b><br>
+
+    Here are some random numbers for you:
+
+    <ul>
+      <li v-for="n in randomNumbers" :key="n">
+        {{ n }}
+      </li>
+    </ul>
+    <button @click="() => refresh()">
+      Give me another set
+    </button>
+  </div>
+</template>
+
+<script setup lang="ts">
+const route = useRoute()
+
+const pageKey = 'rand_' + route.params.id
+
+const { data: randomNumbers, refresh } = await useFetch('/api/random', { key: pageKey as string })
+
+const random = useRandomState(100, pageKey)
+const globalRandom = useRandomState(100)
+
+// TODO: NuxtLink should do this automatically on observed
+if (process.client) {
+  preloadPayload('/random/c')
+}
+</script>

test/fixtures/basic/plugins/prerender.server.ts

@@ -0,0 +1,4 @@
+export default defineNuxtPlugin((nuxtApp) => {
+  // Pretend to be prerendered
+  nuxtApp.payload.prerenderedAt = Date.now()
+})

test/fixtures/basic/server/api/random.ts

@@ -0,0 +1,3 @@
+export default eventHandler(() => {
+  return new Array(10).fill(0).map(() => Math.round(Math.random() * 10000))
+})