fix: fallback linked message params

packages/core-base/src/runtime.ts

@@ -17,10 +17,10 @@ type ExtractToStringKey<T> = Extract<keyof T, 'toString'>
 type ExtractToStringFunction<T> = T[ExtractToStringKey<T>]
 // prettier-ignore
 type StringConvertable<T> = ExtractToStringKey<T> extends never
-	? unknown
-	: ExtractToStringFunction<T> extends (...args: any) => string // eslint-disable-line @typescript-eslint/no-explicit-any
-	  ? T
-	  : unknown
+  ? unknown
+  : ExtractToStringFunction<T> extends (...args: any) => string // eslint-disable-line @typescript-eslint/no-explicit-any
+  ? T
+  : unknown
 
 /**
  *
@@ -110,7 +110,8 @@ export type MessageFunction<T = string> =
 
 export type MessageFunctions<T = string> = Record<string, MessageFunction<T>>
 export type MessageResolveFunction<T = string> = (
-  key: string
+  key: string,
+  useLinked: boolean
 ) => MessageFunction<T>
 
 export type MessageNormalize<T = string> = (
@@ -310,27 +311,27 @@ function pluralDefault(choice: number, choicesLength: number): number {
   if (choicesLength === 2) {
     // prettier-ignore
     return choice
-	    ? choice > 1
-	      ? 1
-	      : 0
-	    : 1
+      ? choice > 1
+        ? 1
+        : 0
+      : 1
   }
   return choice ? Math.min(choice, 2) : 0
 }
 
 function getPluralIndex<T, N>(options: MessageContextOptions<T, N>): number {
   // prettier-ignore
   const index = isNumber(options.pluralIndex)
-	  ? options.pluralIndex
-	  : -1
+    ? options.pluralIndex
+    : -1
   // prettier-ignore
   return options.named && (isNumber(options.named.count) || isNumber(options.named.n))
-	  ? isNumber(options.named.count)
-	    ? options.named.count
-	    : isNumber(options.named.n)
-	      ? options.named.n
-	      : index
-	  : index
+    ? isNumber(options.named.count)
+      ? options.named.count
+      : isNumber(options.named.n)
+        ? options.named.n
+        : index
+    : index
 }
 
 function normalizeNamed(pluralIndex: number, props: PluralizationProps): void {
@@ -371,13 +372,13 @@ export function createMessageContext<T = string, N = {}>(
   isNumber(options.pluralIndex) && normalizeNamed(pluralIndex, _named)
   const named = (key: string): unknown => _named[key]
 
-  function message(key: Path): MessageFunction<T> {
+  function message(key: Path, useLinked?: boolean): MessageFunction<T> {
     // prettier-ignore
     const msg = isFunction(options.messages)
-	    ? options.messages(key)
-	    : isObject(options.messages)
-	      ? options.messages[key]
-	      : false
+      ? options.messages(key, !!useLinked)
+      : isObject(options.messages)
+        ? options.messages[key]
+        : false
     return !msg
       ? options.parent
         ? options.parent.message(key) // resolve from parent messages
@@ -425,7 +426,7 @@ export function createMessageContext<T = string, N = {}>(
         type = arg2 || type
       }
     }
-    const ret = message(key)(ctx)
+    const ret = message(key, true)(ctx)
     const msg =
       // The message in vnode resolved with linked are returned as an array by processor.nomalize
       type === 'vnode' && isArray(ret) && modifier

packages/core-base/src/translate.ts

@@ -1156,13 +1156,16 @@ function getMessageContextOptions<Messages, Message = string>(
     fallbackContext
   } = context
 
-  const resolveMessage = (key: string): MessageFunction<Message> => {
+  const resolveMessage = (
+    key: string,
+    useLinked: boolean
+  ): MessageFunction<Message> => {
     let val = resolveValue(message, key)
 
-    // fallback to root context
-    if (val == null && fallbackContext) {
+    // fallback
+    if (val == null && (fallbackContext || useLinked)) {
       const [, , message] = resolveMessageFormat(
-        fallbackContext,
+        fallbackContext || context, // NOTE: if has fallbackContext, fallback to root, else if use linked, fallback to local context
         key,
         locale,
         fallbackLocale as FallbackLocale,

packages/core-base/test/translate.test.ts

@@ -810,23 +810,45 @@ describe('edge cases', () => {
   })
 })
 
-test('fallback context', () => {
-  const parent = context({
-    locale: 'en',
-    messages: {
-      en: { hello: 'hello man!', hi: 'hi' }
-    }
-  })
+describe('fallback context', () => {
+  test('root (parent context)', () => {
+    const parent = context({
+      locale: 'en',
+      messages: {
+        en: { hello: 'hello man!', hi: 'hi' }
+      }
+    })
 
-  const ctx = context({
-    locale: 'en',
-    messages: {
-      en: { hi: 'hi! @:hello' }
-    }
+    const ctx = context({
+      locale: 'en',
+      messages: {
+        en: { hi: 'hi! @:hello' }
+      }
+    })
+    ctx.fallbackContext = parent
+
+    expect(translate(ctx, 'hi')).toEqual('hi! hello man!')
   })
-  ctx.fallbackContext = parent
 
-  expect(translate(ctx, 'hi')).toEqual('hi! hello man!')
+  test('local (self context)', () => {
+    const ctx = context({
+      locale: 'en',
+      messages: {
+        en: {
+          apples: 'Apples',
+          no_results: 'No @.lower:{0} found'
+        },
+        'en-variant': {
+          no_results: 'No @.lower:{0} found'
+        }
+      }
+    })
+
+    expect(translate(ctx, 'no_results', ['apples'])).toEqual('No apples found')
+    expect(
+      translate(ctx, 'no_results', ['apples'], { locale: 'en-variant' })
+    ).toEqual('No apples found')
+  })
 })
 
 describe('processor', () => {

packages/vue-i18n-core/test/issues.test.ts

@@ -1359,3 +1359,50 @@ test('#1809', async () => {
   })
   expect(i18n.global.t('hi')).toEqual('hi kazupon')
 })
+
+test('#1912', async () => {
+  const i18n = createI18n({
+    legacy: false,
+    locale: 'en',
+    messages: {
+      en: {
+        hello: 'Hello, Vue I18n',
+        language: 'Languages',
+        apples: 'Apples',
+        no_results: 'No @.lower:{0} found'
+      },
+      'en-variant': {
+        no_results: 'No @.lower:{0} found'
+      }
+    }
+  })
+
+  let loc: ReturnType<typeof useI18n>['locale']
+  const App = defineComponent({
+    template: `
+  <form>
+    <select v-model="locale">
+      <option value="en">en</option>
+      <option value="en-variant">en-variant</option>
+    </select>
+  </form>
+  <p>{{ t('no_results', ['apples']) }}</p>
+`,
+    setup() {
+      const { t, locale } = useI18n()
+      // @ts-ignore
+      loc = locale
+      return { t, locale }
+    }
+  })
+  const wrapper = await mount(App, i18n)
+  await nextTick()
+
+  const el = wrapper.find('p')
+  expect(el?.innerHTML).include(`No apples found`)
+  // @ts-ignore
+  loc.value = 'en-variant'
+  await nextTick()
+
+  expect(el?.innerHTML).include(`No apples found`)
+})