fix: unable to configure server integration using inline options

specs/fixtures/inline_options/locale-detector.ts

@@ -0,0 +1,23 @@
+// Detect based on query, cookie, header
+export default defineI18nLocaleDetector((event, config) => {
+  // try to get locale from query
+  const query = tryQueryLocale(event, { lang: '' }) // disable locale default value with `lang` option
+  if (query) {
+    return query.toString()
+  }
+
+  // try to get locale from cookie
+  const cookie = tryCookieLocale(event, { lang: '', name: 'i18n_locale' }) // disable locale default value with `lang` option
+  if (cookie) {
+    return cookie.toString()
+  }
+
+  // try to get locale from header (`accept-header`)
+  const header = tryHeaderLocale(event, { lang: '' }) // disable locale default value with `lang` option
+  if (header) {
+    return header.toString()
+  }
+
+  // If the locale cannot be resolved up to this point, it is resolved with the value `defaultLocale` of the locale config passed to the function
+  return config.defaultLocale
+})

specs/fixtures/inline_options/nuxt.config.ts

@@ -19,7 +19,10 @@ export default defineNuxtConfig({
             file: 'locale-file-en.json',
             name: 'English'
           }
-        ]
+        ],
+        experimental: {
+          localeDetector: './locale-detector.ts'
+        }
       }
     ]
   ],

specs/fixtures/inline_options/server/api/translate.ts

@@ -0,0 +1,7 @@
+import { useTranslation } from '@intlify/h3'
+
+export default defineEventHandler(async event => {
+  const t = await useTranslation(event)
+
+  return t('home')
+})

specs/inline_options.spec.ts

@@ -1,6 +1,6 @@
 import { test, expect, describe } from 'vitest'
 import { fileURLToPath } from 'node:url'
-import { setup } from './utils'
+import { setup, url, $fetch } from './utils'
 import { renderPage } from './helper'
 
 await setup({
@@ -34,4 +34,9 @@ describe('inline options are handled correctly', async () => {
       )
     ).toBe(false)
   })
+
+  test('(#2721) server integration from inline configuration', async () => {
+    const res = await $fetch(url('/api/translate'))
+    expect(res).toEqual('Homepage')
+  })
 })

src/nitro.ts

@@ -7,7 +7,7 @@ import { addServerPlugin, createResolver, resolvePath, useLogger } from '@nuxt/k
 import yamlPlugin from '@rollup/plugin-yaml'
 import json5Plugin from '@miyaneee/rollup-plugin-json5'
 import { getFeatureFlags } from './bundler'
-import { isExists } from './utils'
+import { getLayerI18n, isExists } from './utils'
 import {
   H3_PKG,
   UTILS_H3_PKG,
@@ -130,13 +130,16 @@ export { localeDetector }
 }
 
 async function resolveLocaleDetectorPath(nuxt: Nuxt) {
-  const serverI18nLayer = nuxt.options._layers.find(
-    l => l.config.i18n?.experimental?.localeDetector != null && l.config.i18n?.experimental?.localeDetector !== ''
-  )
+  const serverI18nLayer = nuxt.options._layers.find(l => {
+    const layerI18n = getLayerI18n(l)
+    return layerI18n?.experimental?.localeDetector != null && layerI18n?.experimental?.localeDetector !== ''
+  })
+
   let enableServerIntegration = serverI18nLayer != null
 
   if (serverI18nLayer != null) {
-    const pathTo = resolve(serverI18nLayer.config.rootDir, serverI18nLayer.config.i18n!.experimental!.localeDetector!)
+    const serverI18nLayerConfig = getLayerI18n(serverI18nLayer)
+    const pathTo = resolve(serverI18nLayer.config.rootDir, serverI18nLayerConfig!.experimental!.localeDetector!)
     const localeDetectorPath = await resolvePath(pathTo, {
       cwd: nuxt.options.rootDir,
       extensions: EXECUTABLE_EXTENSIONS