feat: how to get locale messages from a given key (#87)

* feat: the way to get locale messages from the specified key

* update docs

README.md

@@ -60,7 +60,6 @@ See the below examples:
 - [Example with using Composable API](https://github.com/intlify/vue-i18n-next/blob/master/examples/composable/components/datetime-format.html)
 - [Example with using Legacy API](https://github.com/intlify/vue-i18n-next/blob/master/examples/legacy/components/datetime-format.html)
 
-
 ## :lollipop: Examples
 
 See the [`examples`](https://github.com/intlify/vue-i18n-next/tree/master/examples) directory.
@@ -79,7 +78,9 @@ The examples are offered that use the following two API styles:
 
 #### APIs
 - The return value of `$t` and `t` methods is **string** only. object and array values ​​are no longer returned.
+  - As an alternative way, you can use `$tm` / `tm`
 - The return value of `$tc` and `tc` methods is **string** only. object and array values ​​are no longer returned.
+  - As an alternative way, you can use `$tm` / `tm`
 - `VueI18n` class cannot used with `new`. It can only be used via the `$i18n` property of Vue instance.
   - In vue-i18n-next, by replacing `new VueI18n` with `createI18n`, you can use existing `VueI18n` options as they are.
   - See the `examples/legacy` directory.
@@ -191,6 +192,7 @@ yarn add vue-i18n@next
     - [x] setPostTranslationHandler
     - [x] getMissingHandler
     - [x] setMissingHandler
+    - [x] tm
 - Legacy API: compatible supporting
   - VueI18n
     - [x] locale
@@ -225,13 +227,15 @@ yarn add vue-i18n@next
     - [x] setNumberFormat
     - [x] mergeNumberFormat
     - [x] getChoiceIndex
+    - [x] tm
   - Inejctted in Vue Prototype API
     - [x] $i18n
     - [x] $t
     - [x] $tc
     - [x] $te
     - [x] $d
     - [x] $n
+    - [x] $tm
   - Component options
     - [x] messages
     - [x] pluralRule

src/composer.ts

@@ -17,7 +17,7 @@ import {
   VNodeArrayChildren
 } from 'vue'
 import { WritableComputedRef, ComputedRef } from '@vue/reactivity'
-import { Path, parse as parsePath } from './path'
+import { Path, parse as parsePath, resolveValue } from './path'
 import {
   DateTimeFormats as DateTimeFormatsType,
   NumberFormats as NumberFormatsType,
@@ -34,6 +34,7 @@ import {
 } from './message/runtime'
 import {
   Locale,
+  LocaleMessageValue,
   LocaleMessages,
   createRuntimeContext,
   RuntimeContext,
@@ -195,6 +196,7 @@ export interface Composer<
   n(value: number, key: string, locale: Locale): string
   n(value: number, options: NumberOptions): string
   n(...args: unknown[]): string // for internal
+  tm(key: Path): LocaleMessageValue<Message> | {}
   getLocaleMessage(locale: Locale): LocaleMessageDictionary<Message>
   setLocaleMessage(
     locale: Locale,
@@ -696,6 +698,18 @@ export function createComposer<
     )
   }
 
+  // tm
+  function tm(key: Path): LocaleMessageValue<Message> | {} {
+    const messages = _messages.value[_locale.value] || {}
+    const target = resolveValue(messages, key)
+    // prettier-ignore
+    return target != null
+      ? target as LocaleMessageValue<Message>
+      : __root
+        ? __root.tm(key) as LocaleMessageValue<Message> || {}
+        : {}
+  }
+
   // getLocaleMessage
   function getLocaleMessage(locale: Locale): LocaleMessageDictionary<Message> {
     return (_messages.value[locale] || {}) as LocaleMessageDictionary<Message>
@@ -869,6 +883,7 @@ export function createComposer<
     t,
     d,
     n,
+    tm,
     getLocaleMessage,
     setLocaleMessage,
     mergeLocaleMessage,

src/legacy.ts

@@ -16,7 +16,8 @@ import {
   LocaleMessages,
   LocaleMessageDictionary,
   PostTranslationHandler,
-  FallbackLocale
+  FallbackLocale,
+  LocaleMessageValue
 } from './core/context'
 import { TranslateOptions } from './core/translate'
 import {
@@ -139,6 +140,7 @@ export interface VueI18n<
   tc(key: Path, choice: number, named: Record<string, unknown>): TranslateResult
   tc(...args: unknown[]): TranslateResult // for $tc
   te(key: Path, locale?: Locale): boolean
+  tm(key: Path): LocaleMessageValue<VueMessageType> | {}
   getLocaleMessage(locale: Locale): LocaleMessageDictionary<VueMessageType>
   setLocaleMessage(
     locale: Locale,
@@ -510,6 +512,11 @@ export function createVueI18n<
       return resolveValue(message, key) !== null
     },
 
+    // tm
+    tm(key: Path): LocaleMessageValue<VueMessageType> | {} {
+      return composer.tm(key)
+    },
+
     // getLocaleMessage
     getLocaleMessage(locale: Locale): LocaleMessageDictionary<VueMessageType> {
       return composer.getLocaleMessage(locale)

src/mixin.ts

@@ -1,7 +1,12 @@
 import { ComponentOptions, getCurrentInstance } from 'vue'
 import { Path } from './path'
-import { Locale } from './core/context'
-import { Composer, ComposerInternalOptions, CustomBlocks } from './composer'
+import { Locale, LocaleMessageValue } from './core/context'
+import {
+  Composer,
+  ComposerInternalOptions,
+  CustomBlocks,
+  VueMessageType
+} from './composer'
 import {
   VueI18n,
   VueI18nInternal,
@@ -134,6 +139,20 @@ declare module '@vue/runtime-core' {
      * This property is supported for legacy API only
      */
     $n?: (...args: unknown[]) => NumberFormatResult
+    /**
+     * translation messages method
+     *
+     * @param key - required, target keypath
+     * @returns locale messages
+     *
+     * @remarks
+     * Get the locale message of `key`.
+     * Get in preferentially component locale messages than global locale messages.
+     * If the target locale messages is not found locally, get it from the global, otherwise returns an empty object.
+     *
+     * This property is supported for legacy API only
+     */
+    $tm?: (key: Path) => LocaleMessageValue<VueMessageType> | {}
   }
 }
 
@@ -206,6 +225,8 @@ export function defineMixin<Messages, DateTimeFormats, NumberFormats>(
         this.$i18n.d(...args)
       this.$n = (...args: unknown[]): NumberFormatResult =>
         this.$i18n.n(...args)
+      this.$tm = (key: Path): LocaleMessageValue<VueMessageType> | {} =>
+        this.$i18n.tm(key)
     },
 
     mounted(): void {
@@ -226,6 +247,7 @@ export function defineMixin<Messages, DateTimeFormats, NumberFormats>(
       delete this.$te
       delete this.$d
       delete this.$n
+      delete this.$tm
 
       i18n.__deleteInstance(instance)
       delete this.$i18n

test/composer.test.ts

@@ -16,7 +16,7 @@ import {
   VueMessageType
 } from '../src/composer'
 import { generateFormatCacheKey } from '../src/utils'
-import { watch, nextTick, Text, createVNode } from 'vue'
+import { watch, watchEffect, nextTick, Text, createVNode } from 'vue'
 
 describe('locale', () => {
   test('default value', () => {
@@ -670,6 +670,41 @@ describe('n', () => {
   })
 })
 
+test('tm', async () => {
+  const composer = createComposer({
+    locale: 'ja',
+    messages: {
+      en: {},
+      ja: {
+        foo: {
+          bar: {
+            buz: 'hello'
+          },
+          codes: {
+            errors: ['error1', 'error2']
+          }
+        }
+      }
+    }
+  })
+
+  let messages1 = composer.tm('foo.bar')
+  let messages2 = composer.tm('foo.codes')
+  expect(messages1).toEqual({ buz: 'hello' })
+  expect(messages2).toEqual({ errors: ['error1', 'error2'] })
+
+  watchEffect(() => {
+    messages1 = composer.tm('foo.bar')
+    messages2 = composer.tm('foo.codes')
+  })
+
+  composer.locale.value = 'en'
+  await nextTick()
+
+  expect(messages1).toEqual({})
+  expect(messages2).toEqual({})
+})
+
 describe('getLocaleMessage / setLocaleMessage / mergeLocaleMessage', () => {
   test('basic', () => {
     const {

test/legacy.test.ts

@@ -10,6 +10,7 @@ import { warn } from '../src/utils'
 import { createVueI18n } from '../src/legacy'
 import { errorMessages, I18nErrorCodes } from '../src/errors'
 import { getWarnMessage, I18nWarnCodes } from '../src/warnings'
+import { watchEffect, nextTick } from 'vue'
 
 test('locale', () => {
   const i18n = createVueI18n()
@@ -234,6 +235,41 @@ test('te', () => {
   expect(i18n.te('message.hallo', 'ja')).toEqual(false)
 })
 
+test('tm', async () => {
+  const i18n = createVueI18n({
+    locale: 'ja',
+    messages: {
+      en: {},
+      ja: {
+        foo: {
+          bar: {
+            buz: 'hello'
+          },
+          codes: {
+            errors: ['error1', 'error2']
+          }
+        }
+      }
+    }
+  })
+
+  let messages1 = i18n.tm('foo.bar')
+  let messages2 = i18n.tm('foo.codes')
+  expect(messages1).toEqual({ buz: 'hello' })
+  expect(messages2).toEqual({ errors: ['error1', 'error2'] })
+
+  watchEffect(() => {
+    messages1 = i18n.tm('foo.bar')
+    messages2 = i18n.tm('foo.codes')
+  })
+
+  i18n.locale = 'en'
+  await nextTick()
+
+  expect(messages1).toEqual({})
+  expect(messages2).toEqual({})
+})
+
 test('getLocaleMessage / setLocaleMessage / mergeLocaleMessage', () => {
   const i18n = createVueI18n({
     messages: {