fix: skip optimizing dynamic locale files (#4058)

Author: BobbieGoede

specs/fixtures/lazy/app.vue specs/fixtures/lazy/app/app.vuespecs/fixtures/lazy/app.vue renamed to specs/fixtures/lazy/app/app.vue

@@ -0,0 +1,20 @@
+import { test, expect, describe } from 'vitest'
+import { fileURLToPath } from 'node:url'
+import { setup, $fetch } from '../utils'
+
+describe('lazy loading (dev mode + app directory)', async () => {
+  await setup({
+    rootDir: fileURLToPath(new URL(`../fixtures/lazy`, import.meta.url)),
+    dev: true
+  })
+
+  test('(#4049) dynamic locale files are loaded during dev SSR', async () => {
+    const html: string = await $fetch('/en-GB')
+    // dynamic `.js` locale file fetching `/api/en-GB`
+    expect(html).toContain('Profile1')
+    // static `.ts` locale file
+    expect(html).toContain('Profile2')
+    // dynamic locale file using `useRuntimeConfig`
+    expect(html).toContain('runtime-config-value')
+  })
+})

specs/fixtures/lazy/pages/about/index.vue …/fixtures/lazy/app/pages/about/index.vuespecs/fixtures/lazy/pages/about/index.vue renamed to specs/fixtures/lazy/app/pages/about/index.vue specs/fixtures/lazy/pages/about/index.vue renamed to specs/fixtures/lazy/app/pages/about/index.vue

@@ -34,7 +34,9 @@ export async function extendBundler(ctx: I18nNuxtContext, nuxt: Nuxt) {
   /**
    * shared plugins (vite/webpack/rspack)
    */
-  const localePaths = getLocaleFilePaths(ctx.localeInfo)
+  // exclude dynamic locale files - optimization is a no-op for these, and since vite 8 matching them
+  // makes unplugin-vue-i18n load them raw during dev SSR, skipping the `defineI18nLocale` transform (#4049)
+  const localePaths = getLocaleFilePaths(ctx.localeInfo.map(x => ({ ...x, meta: x.meta.filter(m => m.type !== 'dynamic') })))
   ctx.fullStatic = ctx.localeInfo.flatMap(x => x.meta).every(x => x.type === 'static' || x.cache !== false)
 
   const vueI18nPluginOptions: PluginOptions = {
@@ -47,7 +49,6 @@ export async function extendBundler(ctx: I18nNuxtContext, nuxt: Nuxt) {
   }
   addBuildPlugin({
     vite: () => VueI18nPlugin.vite(vueI18nPluginOptions),
-
     webpack: () => VueI18nPlugin.webpack(vueI18nPluginOptions),
   })
   addBuildPlugin(TransformMacroPlugin(pluginOptions))

specs/fixtures/lazy/pages/index.vue specs/fixtures/lazy/app/pages/index.vuespecs/fixtures/lazy/pages/index.vue renamed to specs/fixtures/lazy/app/pages/index.vue

@@ -1,6 +1,6 @@
 import MagicString from 'magic-string'
 import { createUnplugin } from 'unplugin'
-import { NUXT_I18N_VIRTUAL_PREFIX, VIRTUAL_PREFIX_HEX, asI18nVirtual } from './utils'
+import { VIRTUAL_PREFIX_HEX, asI18nVirtual } from './utils'
 import { dirname, resolve } from 'pathe'
 import { findStaticImports } from 'mlly'
 import { resolvePath, tryUseNuxt } from '@nuxt/kit'
@@ -35,10 +35,16 @@ export const ResourcePlugin = (options: BundlerPluginOptions, ctx: I18nNuxtConte
 
       // resolve virtual hash to file path
       resolveId(id) {
-        if (!id || id.startsWith(VIRTUAL_PREFIX_HEX) || !id.startsWith(NUXT_I18N_VIRTUAL_PREFIX)) {
+        if (!id || id.startsWith(VIRTUAL_PREFIX_HEX)) {
           return
         }
 
+        // claim i18n file paths so other plugins (e.g. `unplugin-vue-i18n` since vite 8) cannot
+        // resolve these to virtual modules loaded from disk, which would skip our transforms (#4049)
+        if (i18nPathSet.has(id)) {
+          return id
+        }
+
         if (i18nFileHashSet.has(id)) {
           return i18nFileHashSet.get(id)
         }