feat(nuxt): namespace __NUXT__ when using multi-app (#27263)

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

@@ -9,7 +9,7 @@ import { useRoute } from './router'
 import { getAppManifest, getRouteRules } from './manifest'
 
 // @ts-expect-error virtual import
-import { appManifest, payloadExtraction, renderJsonPayloads } from '#build/nuxt.config.mjs'
+import { appId, appManifest, multiApp, payloadExtraction, renderJsonPayloads } from '#build/nuxt.config.mjs'
 
 interface LoadPayloadOptions {
   fresh?: boolean
@@ -107,7 +107,7 @@ export async function getNuxtClientPayload () {
     return payloadCache
   }
 
-  const el = document.getElementById('__NUXT_DATA__')
+  const el = multiApp ? document.querySelector(`[data-nuxt-data="${appId}"]`) as HTMLElement : document.getElementById('__NUXT_DATA__')
   if (!el) {
     return {} as Partial<NuxtPayload>
   }
@@ -119,7 +119,7 @@ export async function getNuxtClientPayload () {
   payloadCache = {
     ...inlineData,
     ...externalData,
-    ...window.__NUXT__,
+    ...(multiApp ? window.__NUXT__?.[appId] : window.__NUXT__),
   }
 
   if (payloadCache!.config?.public) {

packages/nuxt/src/app/entry.ts

@@ -15,7 +15,7 @@ import plugins from '#build/plugins'
 // @ts-expect-error virtual file
 import RootComponent from '#build/root-component.mjs'
 // @ts-expect-error virtual file
-import { vueAppRootContainer } from '#build/nuxt.config.mjs'
+import { appId, multiApp, vueAppRootContainer } from '#build/nuxt.config.mjs'
 
 let entry: (ssrContext?: CreateOptions['ssrContext']) => Promise<App<Element>>
 
@@ -50,9 +50,10 @@ if (import.meta.client) {
 
   entry = async function initApp () {
     if (vueAppPromise) { return vueAppPromise }
+
     const isSSR = Boolean(
-      window.__NUXT__?.serverRendered ||
-      document.getElementById('__NUXT_DATA__')?.dataset.ssr === 'true',
+      (multiApp ? window.__NUXT__?.[appId] : window.__NUXT__)?.serverRendered ??
+      (multiApp ? document.querySelector(`[data-nuxt-data="${appId}"]`) as HTMLElement : document.getElementById('__NUXT_DATA__'))?.dataset.ssr === 'true',
     )
     const vueApp = isSSR ? createSSRApp(RootComponent) : createApp(RootComponent)
 

packages/nuxt/src/app/nuxt.ts

@@ -21,7 +21,7 @@ import type { RouteAnnouncer } from '../app/composables/route-announcer'
 import type { ViewTransition } from './plugins/view-transitions.client'
 
 // @ts-expect-error virtual file
-import { appId } from '#build/nuxt.config.mjs'
+import { appId, multiApp } from '#build/nuxt.config.mjs'
 
 // TODO: temporary module for backwards compatibility
 import type { DefaultAsyncDataErrorValue, DefaultErrorValue } from '#app/defaults'
@@ -315,19 +315,22 @@ export function createNuxtApp (options: CreateOptions) {
     nuxtApp.payload.serverRendered = true
   }
 
-  // TODO: remove/refactor in https://github.com/nuxt/nuxt/issues/25336
-  if (import.meta.client && window.__NUXT__) {
-    for (const key in window.__NUXT__) {
-      switch (key) {
-        case 'data':
-        case 'state':
-        case '_errors':
-          // Preserve reactivity for non-rich payload support
-          Object.assign(nuxtApp.payload[key], window.__NUXT__[key])
-          break
+  if (import.meta.client) {
+    const __NUXT__ = multiApp ? window.__NUXT__?.[nuxtApp._id] : window.__NUXT__
+    // TODO: remove/refactor in https://github.com/nuxt/nuxt/issues/25336
+    if (__NUXT__) {
+      for (const key in __NUXT__) {
+        switch (key) {
+          case 'data':
+          case 'state':
+          case '_errors':
+            // Preserve reactivity for non-rich payload support
+            Object.assign(nuxtApp.payload[key], __NUXT__[key])
+            break
 
-        default:
-          nuxtApp.payload[key] = window.__NUXT__[key]
+          default:
+            nuxtApp.payload[key] = __NUXT__[key]
+        }
       }
     }
   }

packages/nuxt/src/app/plugins/dev-server-logs.ts

@@ -40,7 +40,8 @@ export default defineNuxtPlugin(async (nuxtApp) => {
   }
 
   if (typeof window !== 'undefined') {
-    const content = document.getElementById('__NUXT_LOGS__')?.textContent
+    const nuxtLogsElement = document.querySelector(`[data-nuxt-logs="${nuxtApp._name}"]`)
+    const content = nuxtLogsElement?.textContent
     const logs = content ? parse(content, { ...devRevivers, ...nuxtApp._payloadRevivers }) as LogObject[] : []
     await nuxtApp.hooks.callHook('dev:ssr-logs', logs)
   }

packages/nuxt/src/app/types/augments.d.ts

@@ -26,7 +26,7 @@ declare global {
   }
 
   interface Window {
-    __NUXT__?: Record<string, any>
+    __NUXT__?: Record<string, any> | Record<string, Record<string, any>>
     useNuxtApp?: typeof useNuxtApp
   }
 }

packages/nuxt/src/core/runtime/nitro/dev-server-logs.ts

@@ -13,6 +13,8 @@ import type { NitroApp } from '#internal/nitro/app'
 
 // @ts-expect-error virtual file
 import { rootDir } from '#internal/dev-server-logs-options'
+// @ts-expect-error virtual file
+import { appId } from '#internal/nuxt.config.mjs'
 
 const devReducers: Record<string, (data: any) => any> = {
   VNode: data => isVNode(data) ? { type: data.type, props: data.props } : undefined,
@@ -75,7 +77,7 @@ export default (nitroApp: NitroApp) => {
     const ctx = asyncContext.tryUse()
     if (!ctx) { return }
     try {
-      htmlContext.bodyAppend.unshift(`<script type="application/json" id="__NUXT_LOGS__">${stringify(ctx.logs, { ...devReducers, ...ctx.event.context._payloadReducers })}</script>`)
+      htmlContext.bodyAppend.unshift(`<script type="application/json" data-nuxt-logs="${appId}">${stringify(ctx.logs, { ...devReducers, ...ctx.event.context._payloadReducers })}</script>`)
     } catch (e) {
       const shortError = e instanceof Error && 'toString' in e ? ` Received \`${e.toString()}\`.` : ''
       console.warn(`[nuxt] Failed to stringify dev server logs.${shortError} You can define your own reducer/reviver for rich types following the instructions in https://nuxt.com/docs/api/composables/use-nuxt-app#payload.`)

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

@@ -32,7 +32,7 @@ import { renderSSRHeadOptions } from '#internal/unhead.config.mjs'
 
 import type { NuxtPayload, NuxtSSRContext } from '#app'
 // @ts-expect-error virtual file
-import { appHead, appRootAttrs, appRootTag, appTeleportAttrs, appTeleportTag, componentIslands } from '#internal/nuxt.config.mjs'
+import { appHead, appId, appRootAttrs, appRootTag, appTeleportAttrs, appTeleportTag, componentIslands, multiApp } from '#internal/nuxt.config.mjs'
 // @ts-expect-error virtual file
 import { buildAssetsURL, publicAssetsURL } from '#internal/nuxt/paths'
 
@@ -428,10 +428,10 @@ export default defineRenderHandler(async (event): Promise<Partial<RenderResponse
     head.push({
       script: _PAYLOAD_EXTRACTION
         ? process.env.NUXT_JSON_PAYLOADS
-          ? renderPayloadJsonScript({ id: '__NUXT_DATA__', ssrContext, data: splitPayload(ssrContext).initial, src: payloadURL })
+          ? renderPayloadJsonScript({ ssrContext, data: splitPayload(ssrContext).initial, src: payloadURL })
           : renderPayloadScript({ ssrContext, data: splitPayload(ssrContext).initial, src: payloadURL })
         : process.env.NUXT_JSON_PAYLOADS
-          ? renderPayloadJsonScript({ id: '__NUXT_DATA__', ssrContext, data: ssrContext.payload })
+          ? renderPayloadJsonScript({ ssrContext, data: ssrContext.payload })
           : renderPayloadScript({ ssrContext, data: ssrContext.payload }),
     }, {
       ...headEntryOptions,
@@ -587,21 +587,27 @@ function renderPayloadResponse (ssrContext: NuxtSSRContext) {
   } satisfies RenderResponse
 }
 
-function renderPayloadJsonScript (opts: { id: string, ssrContext: NuxtSSRContext, data?: any, src?: string }): Script[] {
+function renderPayloadJsonScript (opts: { ssrContext: NuxtSSRContext, data?: any, src?: string }): Script[] {
   const contents = opts.data ? stringify(opts.data, opts.ssrContext._payloadReducers) : ''
   const payload: Script = {
     'type': 'application/json',
-    'id': opts.id,
     'innerHTML': contents,
+    'data-nuxt-data': appId,
     'data-ssr': !(process.env.NUXT_NO_SSR || opts.ssrContext.noSSR),
   }
+  if (!multiApp) {
+    payload.id = '__NUXT_DATA__'
+  }
   if (opts.src) {
     payload['data-src'] = opts.src
   }
+  const config = uneval(opts.ssrContext.config)
   return [
     payload,
     {
-      innerHTML: `window.__NUXT__={};window.__NUXT__.config=${uneval(opts.ssrContext.config)}`,
+      innerHTML: multiApp
+        ? `window.__NUXT__=window.__NUXT__||{};window.__NUXT__[${JSON.stringify(appId)}]={config:${config}}`
+        : `window.__NUXT__={};window.__NUXT__.config=${config}`,
     },
   ]
 }
@@ -609,17 +615,22 @@ function renderPayloadJsonScript (opts: { id: string, ssrContext: NuxtSSRContext
 function renderPayloadScript (opts: { ssrContext: NuxtSSRContext, data?: any, src?: string }): Script[] {
   opts.data.config = opts.ssrContext.config
   const _PAYLOAD_EXTRACTION = import.meta.prerender && process.env.NUXT_PAYLOAD_EXTRACTION && !opts.ssrContext.noSSR
+  const nuxtData = devalue(opts.data)
   if (_PAYLOAD_EXTRACTION) {
+    const singleAppPayload = `import p from "${opts.src}";window.__NUXT__={...p,...(${nuxtData})}`
+    const multiAppPayload = `import p from "${opts.src}";window.__NUXT__=window.__NUXT__||{};window.__NUXT__[${JSON.stringify(appId)}]={...p,...(${nuxtData})}`
     return [
       {
         type: 'module',
-        innerHTML: `import p from "${opts.src}";window.__NUXT__={...p,...(${devalue(opts.data)})}`,
+        innerHTML: multiApp ? multiAppPayload : singleAppPayload,
       },
     ]
   }
+  const singleAppPayload = `window.__NUXT__=${nuxtData}`
+  const multiAppPayload = `window.__NUXT__=window.__NUXT__||{};window.__NUXT__[${JSON.stringify(appId)}]=${nuxtData}`
   return [
     {
-      innerHTML: `window.__NUXT__=${devalue(opts.data)}`,
+      innerHTML: multiApp ? multiAppPayload : singleAppPayload,
     },
   ]
 }

packages/nuxt/src/core/templates.ts

@@ -304,9 +304,16 @@ declare module 'nitropack' {
 
 export const clientConfigTemplate: NuxtTemplate = {
   filename: 'nitro.client.mjs',
-  getContents: () => `
-export const useRuntimeConfig = () => window?.__NUXT__?.config || {}
-`,
+  getContents: ({ nuxt }) => {
+    const appId = JSON.stringify(nuxt.options.appId)
+    return [
+      'export const useRuntimeConfig = () => ',
+      (!nuxt.options.future.multiApp
+        ? 'window?.__NUXT__?.config || {}'
+        : `window?.__NUXT__?.[${appId}]?.config || {}`)
+        || {},
+    ].join('\n')
+  },
 }
 
 export const appConfigDeclarationTemplate: NuxtTemplate = {
@@ -454,6 +461,7 @@ export const nuxtConfigTemplate: NuxtTemplate = {
       `export const viewTransition = ${ctx.nuxt.options.experimental.viewTransition}`,
       `export const appId = ${JSON.stringify(ctx.nuxt.options.appId)}`,
       `export const outdatedBuildInterval = ${ctx.nuxt.options.experimental.checkOutdatedBuildInterval}`,
+      `export const multiApp = ${!!ctx.nuxt.options.future.multiApp}`,
     ].join('\n\n')
   },
 }

test/utils.ts

@@ -114,7 +114,9 @@ export function parseData (html: string) {
       attrs: {},
     }
   }
-  const { script, attrs = '' } = html.match(/<script type="application\/json" id="__NUXT_DATA__"(?<attrs>[^>]+)>(?<script>.*?)<\/script>/)?.groups || {}
+
+  const regexp = /<script type="application\/json" data-nuxt-data="[^"]+"(?<attrs>[^>]+)>(?<script>.*?)<\/script>/
+  const { script, attrs = '' } = html.match(regexp)?.groups || {}
   const _attrs: Record<string, string> = {}
   for (const attr of attrs.matchAll(/( |^)(?<key>[\w-]+)="(?<value>[^"]+)"/g)) {
     _attrs[attr!.groups!.key!] = attr!.groups!.value!