fix: availableLocales not including configured locales (#3347)

Author: BobbieGoede

specs/basic_usage.spec.ts

@@ -75,6 +75,21 @@ describe('basic usage', async () => {
     expect(await page.url()).include('/user/profile?foo=1')
   })
 
+  test('(#3344) `availableLocales` includes all configured locales', async () => {
+    const { page } = await renderPage('/')
+
+    // @ts-expect-error runtime types
+    expect(await page.evaluate(() => window.useNuxtApp?.().$i18n.availableLocales)).toMatchInlineSnapshot(`
+      [
+        "en",
+        "fr",
+        "ja",
+        "kr",
+        "nl",
+      ]
+    `)
+  })
+
   test('`v-t` directive SSR', async () => {
     const pageHTML = await $fetch('/')
     const pageDOM = getDom(pageHTML)

specs/basic_usage_compat_4.spec.ts

@@ -75,6 +75,21 @@ describe('basic usage - compatibilityVersion: 4', async () => {
     expect(await page.url()).include('/user/profile?foo=1')
   })
 
+  test('(#3344) `availableLocales` includes all configured locales', async () => {
+    const { page } = await renderPage('/')
+
+    // @ts-expect-error runtime types
+    expect(await page.evaluate(() => window.useNuxtApp?.().$i18n.availableLocales)).toMatchInlineSnapshot(`
+      [
+        "en",
+        "fr",
+        "ja",
+        "kr",
+        "nl",
+      ]
+    `)
+  })
+
   test('`v-t` directive SSR', async () => {
     const pageHTML = await $fetch('/')
     const pageDOM = getDom(pageHTML)

src/runtime/plugins/i18n.ts

@@ -66,6 +66,12 @@ export default defineNuxtPlugin({
 
     const vueI18nOptions: I18nOptions = await loadVueI18nOptions(vueI18nConfigs, useNuxtApp())
     vueI18nOptions.messages = vueI18nOptions.messages || {}
+
+    // initialize locale objects to make vue-i18n aware of available locales
+    for (const l of localeCodes) {
+      vueI18nOptions.messages[l] ??= {}
+    }
+
     vueI18nOptions.fallbackLocale = vueI18nOptions.fallbackLocale ?? false
     if (defaultLocaleDomain) {
       vueI18nOptions.locale = defaultLocaleDomain