refactor: unify window.__NUXT__ structure for single and multi app

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 { appId, appManifest, multiApp, payloadExtraction, renderJsonPayloads } from '#build/nuxt.config.mjs'
+import { appId, appManifest, payloadExtraction, renderJsonPayloads } from '#build/nuxt.config.mjs'
 
 interface LoadPayloadOptions {
   fresh?: boolean
@@ -107,7 +107,7 @@ export async function getNuxtClientPayload () {
     return payloadCache
   }
 
-  const el = multiApp ? document.querySelector(`[data-nuxt-data="${appId}"]`) as HTMLElement : document.getElementById('__NUXT_DATA__')
+  const el = document.querySelector(`[data-nuxt-data="${appId}"]`) as HTMLElement
   if (!el) {
     return {} as Partial<NuxtPayload>
   }
@@ -119,7 +119,7 @@ export async function getNuxtClientPayload () {
   payloadCache = {
     ...inlineData,
     ...externalData,
-    ...(multiApp ? window.__NUXT__?.[appId] : window.__NUXT__),
+    ...window.__NUXT__?.[appId],
   }
 
   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 { appId, multiApp, vueAppRootContainer } from '#build/nuxt.config.mjs'
+import { appId, vueAppRootContainer } from '#build/nuxt.config.mjs'
 
 let entry: (ssrContext?: CreateOptions['ssrContext']) => Promise<App<Element>>
 
@@ -52,8 +52,8 @@ if (import.meta.client) {
     if (vueAppPromise) { return vueAppPromise }
 
     const isSSR = Boolean(
-      (multiApp ? window.__NUXT__?.[appId] : window.__NUXT__)?.serverRendered ??
-      (multiApp ? document.querySelector(`[data-nuxt-data="${appId}"]`) as HTMLElement : document.getElementById('__NUXT_DATA__'))?.dataset.ssr === 'true',
+      window.__NUXT__?.[appId]?.serverRendered ??
+      (document.querySelector(`[data-nuxt-data="${appId}"]`) as HTMLElement)?.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, multiApp } from '#build/nuxt.config.mjs'
+import { appId } from '#build/nuxt.config.mjs'
 
 import type { NuxtAppLiterals } from '#app'
 
@@ -311,7 +311,7 @@ export function createNuxtApp (options: CreateOptions) {
   }
 
   if (import.meta.client) {
-    const __NUXT__ = multiApp ? window.__NUXT__?.[nuxtApp._id] : window.__NUXT__
+    const __NUXT__ = window.__NUXT__?.[nuxtApp._id]
     // TODO: remove/refactor in https://github.com/nuxt/nuxt/issues/25336
     if (__NUXT__) {
       for (const key in __NUXT__) {

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

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

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

@@ -30,7 +30,7 @@ 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 } from '#internal/nuxt.config.mjs'
 // @ts-expect-error virtual file
 import { buildAssetsURL, publicAssetsURL } from '#internal/nuxt/paths'
 
@@ -599,9 +599,6 @@ function renderPayloadJsonScript (opts: { ssrContext: NuxtSSRContext, data?: any
     '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
   }
@@ -609,9 +606,7 @@ function renderPayloadJsonScript (opts: { ssrContext: NuxtSSRContext, data?: any
   return [
     payload,
     {
-      innerHTML: multiApp
-        ? `window.__NUXT__=window.__NUXT__||{};window.__NUXT__[${JSON.stringify(appId)}]={config:${config}}`
-        : `window.__NUXT__={};window.__NUXT__.config=${config}`,
+      innerHTML: `window.__NUXT__=window.__NUXT__||{};window.__NUXT__[${JSON.stringify(appId)}]={config:${config}}`,
     },
   ]
 }
@@ -621,20 +616,16 @@ function renderPayloadScript (opts: { ssrContext: NuxtSSRContext, data?: any, sr
   const _PAYLOAD_EXTRACTION = import.meta.prerender && process.env.NUXT_PAYLOAD_EXTRACTION && !opts.ssrContext.noSSR
   const nuxtData = devalue(opts.data)
   if (_PAYLOAD_EXTRACTION) {
-    const singleAppPayload = `import p from "${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: multiApp ? multiAppPayload : singleAppPayload,
+        innerHTML: `import p from "${opts.src}";window.__NUXT__=window.__NUXT__||{};window.__NUXT__[${JSON.stringify(appId)}]={...p,...(${nuxtData})}`,
       },
     ]
   }
-  const singleAppPayload = `window.__NUXT__=${nuxtData}`
-  const multiAppPayload = `window.__NUXT__=window.__NUXT__||{};window.__NUXT__[${JSON.stringify(appId)}]=${nuxtData}`
   return [
     {
-      innerHTML: multiApp ? multiAppPayload : singleAppPayload,
+      innerHTML: `window.__NUXT__=window.__NUXT__||{};window.__NUXT__[${JSON.stringify(appId)}]=${nuxtData}`,
     },
   ]
 }

packages/nuxt/src/core/templates.ts

@@ -353,10 +353,7 @@ export const clientConfigTemplate: NuxtTemplate = {
     const appId = JSON.stringify(nuxt.options.appId)
     return [
       'export const useRuntimeConfig = () => ',
-      (!nuxt.options.future.multiApp
-        ? 'window?.__NUXT__?.config || window?.useNuxtApp?.().payload?.config'
-        : `window?.__NUXT__?.[${appId}]?.config || window?.useNuxtApp?.(${appId}).payload?.config`)
-        || {},
+      `window?.__NUXT__?.[${appId}]?.config || window?.useNuxtApp?.(${appId}).payload?.config`,
     ].join('\n')
   },
 }
@@ -503,7 +500,6 @@ 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')
   },
 }

packages/schema/src/config/experimental.ts

@@ -13,11 +13,6 @@ export default defineUntypedSchema({
      * @type {4}
      */
     compatibilityVersion: 4,
-    /**
-     * This enables early access to the experimental multi-app support.
-     * @see [Nuxt Issue #21635](https://github.com/nuxt/nuxt/issues/21635)
-     */
-    multiApp: false,
     /**
      * This enables 'Bundler' module resolution mode for TypeScript, which is the recommended setting
      * for frameworks like Nuxt and Vite.

test/fixtures/basic/plugins/custom-type-assertion.client.ts

@@ -1,5 +1,5 @@
 export default defineNuxtPlugin((nuxtApp) => {
-  if (nuxtApp.payload.serverRendered && nuxtApp.payload.blinkable !== '<revivified-blink>' && document.querySelector('#__NUXT_DATA__')) {
+  if (nuxtApp.payload.serverRendered && nuxtApp.payload.blinkable !== '<revivified-blink>' && document.querySelector('[data-nuxt-data]')) {
     throw createError({
       message: 'Custom type in Nuxt payload was not revived correctly',
     })