From 49529cb87b67b5bd93bfd5fb6aa3e1a3995fdcd2 Mon Sep 17 00:00:00 2001
From: kazuya kawaguchi <kawakazu80@gmail.com>
Date: Tue, 27 May 2025 23:46:45 +0900
Subject: [PATCH] fix: n() & d() output depending "part" option

---
 packages/vue-i18n-core/src/composer.ts        | 66 ++++++++++--------
 .../vue-i18n-core/test/composer.test-d.ts     | 68 +++++++++++--------
 packages/vue-i18n/src/vue.d.ts                | 18 +++--
 3 files changed, 82 insertions(+), 70 deletions(-)

diff --git a/packages/vue-i18n-core/src/composer.ts b/packages/vue-i18n-core/src/composer.ts
index 9569e1c07..f84e85b7e 100644
--- a/packages/vue-i18n-core/src/composer.ts
+++ b/packages/vue-i18n-core/src/composer.ts
@@ -242,6 +242,8 @@ export interface CustomBlock<Message = VueMessageType> {
 
 export type CustomBlocks<Message = VueMessageType> = Array<CustomBlock<Message>>
 
+type IsPart<O> = O extends { part: infer P } ? P : false
+
 // prettier-ignore
 /**
  * Composer Options
@@ -1116,16 +1118,17 @@ export interface ComposerDateTimeFormatting<
   <
     Value extends number | Date | string = number,
     Key extends string = string,
-    Return extends string | Intl.DateTimeFormatPart[] =
-      | string
-      | Intl.DateTimeFormatPart[]
-  >(
-    value: Value,
-    keyOrOptions:
+    OptionsType extends
+      | Key
+      | ResourceKeys
+      | DateTimeOptions<Key | ResourceKeys, Locales> =
       | Key
       | ResourceKeys
       | DateTimeOptions<Key | ResourceKeys, Locales>
-  ): Return
+  >(
+    value: Value,
+    keyOrOptions: OptionsType
+  ): IsPart<OptionsType> extends true ? Intl.DateTimeFormatPart[] : string
   /**
    * Datetime formatting
    *
@@ -1143,17 +1146,18 @@ export interface ComposerDateTimeFormatting<
   <
     Value extends number | Date | string = number,
     Key extends string = string,
-    Return extends string | Intl.DateTimeFormatPart[] =
-      | string
-      | Intl.DateTimeFormatPart[]
-  >(
-    value: Value,
-    keyOrOptions:
+    OptionsType extends
+      | Key
+      | ResourceKeys
+      | DateTimeOptions<Key | ResourceKeys, Locales> =
       | Key
       | ResourceKeys
-      | DateTimeOptions<Key | ResourceKeys, Locales>,
+      | DateTimeOptions<Key | ResourceKeys, Locales>
+  >(
+    value: Value,
+    keyOrOptions: OptionsType,
     locale: Locales
-  ): Return
+  ): IsPart<OptionsType> extends true ? Intl.DateTimeFormatPart[] : string
 }
 
 /**
@@ -1217,16 +1221,17 @@ export interface ComposerNumberFormatting<
    */
   <
     Key extends string = string,
-    Return extends string | Intl.NumberFormatPart[] =
-      | string
-      | Intl.NumberFormatPart[]
-  >(
-    value: number,
-    keyOrOptions:
+    OptionsType extends
+      | Key
+      | ResourceKeys
+      | NumberOptions<Key | ResourceKeys, Locales> =
       | Key
       | ResourceKeys
       | NumberOptions<Key | ResourceKeys, Locales>
-  ): Return
+  >(
+    value: number,
+    keyOrOptions: OptionsType
+  ): IsPart<OptionsType> extends true ? Intl.NumberFormatPart[] : string
   /**
    * Number Formatting
    *
@@ -1243,17 +1248,18 @@ export interface ComposerNumberFormatting<
    */
   <
     Key extends string = string,
-    Return extends string | Intl.NumberFormatPart[] =
-      | string
-      | Intl.NumberFormatPart[]
-  >(
-    value: number,
-    keyOrOptions:
+    OptionsType extends
+      | Key
+      | ResourceKeys
+      | NumberOptions<Key | ResourceKeys, Locales> =
       | Key
       | ResourceKeys
-      | NumberOptions<Key | ResourceKeys, Locales>,
+      | NumberOptions<Key | ResourceKeys, Locales>
+  >(
+    value: number,
+    keyOrOptions: OptionsType,
     locale: Locales
-  ): Return
+  ): IsPart<OptionsType> extends true ? Intl.NumberFormatPart[] : string
 }
 
 /**
diff --git a/packages/vue-i18n-core/test/composer.test-d.ts b/packages/vue-i18n-core/test/composer.test-d.ts
index 281a8fe6b..4f2c3bf94 100644
--- a/packages/vue-i18n-core/test/composer.test-d.ts
+++ b/packages/vue-i18n-core/test/composer.test-d.ts
@@ -342,55 +342,63 @@ test('strict composer with direct options', () => {
   expectTypeOf(strictDirectComposer.numberFormats.value).toEqualTypeOf<{
     ca: { currency: { style: 'currency'; currencyDisplay: 'symbol' } }
   }>()
+
+  // ComposerDateTimeFormatting
   expectTypeOf(strictDirectComposer.d(new Date())).toEqualTypeOf<string>()
   expectTypeOf(
-    strictDirectComposer.d<Date, string, string>(new Date(), 'short', 'ja-JP')
+    strictDirectComposer.d<Date, string>(new Date(), 'short', 'ja-JP')
   ).toEqualTypeOf<string>()
   expectTypeOf(
     strictDirectComposer.d(new Date(), { key: 'short', locale: 'zh' })
-  ).toEqualTypeOf<string | Intl.DateTimeFormatPart[]>()
+  ).toEqualTypeOf<string>()
   expectTypeOf(
-    strictDirectComposer.d<Date, string, Intl.DateTimeFormatPart[]>(
-      new Date(),
-      {
-        key: 'short',
-        locale: 'zh',
-        part: true
-      }
-    )
-  ).toEqualTypeOf<Intl.DateTimeFormatPart[]>()
+    strictDirectComposer.d<Date, string>(new Date(), 'custom' as any)
+  ).toEqualTypeOf<string>()
   expectTypeOf(
-    strictDirectComposer.d<Date, string, string>(new Date(), 'custom' as any)
+    strictDirectComposer.d(new Date(), {
+      key: 'short',
+      locale: 'zh'
+      //part: undefined
+    })
   ).toEqualTypeOf<string>()
-  expectTypeOf(strictDirectComposer.n(1)).toEqualTypeOf<string>()
-  expectTypeOf(strictDirectComposer.n(1, 'currency', 'zh')).toEqualTypeOf<
-    string | Intl.NumberFormatPart[]
-  >()
   expectTypeOf(
-    strictDirectComposer.n<string, string>(1, 'currency', 'zh')
+    strictDirectComposer.d(new Date(), {
+      key: 'short',
+      locale: 'zh',
+      part: false
+    })
   ).toEqualTypeOf<string>()
   expectTypeOf(
-    strictDirectComposer.n<string, string>(1, { key: 'currency', locale: 'en' })
+    strictDirectComposer.d(new Date(), {
+      key: 'short',
+      locale: 'zh',
+      part: true
+    })
+  ).toEqualTypeOf<Intl.DateTimeFormatPart[]>()
+
+  // ComposerNumberFormatting
+  expectTypeOf(strictDirectComposer.n(1)).toEqualTypeOf<string>()
+  expectTypeOf(
+    strictDirectComposer.n<string, string>(1, 'currency', 'zh')
   ).toEqualTypeOf<string>()
+  expectTypeOf(strictDirectComposer.n(1, 'currency')).toEqualTypeOf<string>()
   expectTypeOf(
-    strictDirectComposer.n<string, string>(1, { key: 'currency', locale: 'en' })
+    strictDirectComposer.n<string>(1, 'currency')
   ).toEqualTypeOf<string>()
+  // part & return type
   expectTypeOf(
-    strictDirectComposer.n<string, Intl.NumberFormatPart[]>(1, {
+    strictDirectComposer.n(1, {
       key: 'currency',
-      locale: 'en',
-      part: true
+      locale: 'en'
+      //part: undefined
     })
-  ).toEqualTypeOf<Intl.NumberFormatPart[]>()
-  expectTypeOf(strictDirectComposer.n(1, 'currency')).toEqualTypeOf<
-    string | Intl.NumberFormatPart[]
-  >()
+  ).toEqualTypeOf<string>()
   expectTypeOf(
-    strictDirectComposer.n<string, string>(1, 'currency')
+    strictDirectComposer.n(1, { key: 'currency', locale: 'en', part: false })
   ).toEqualTypeOf<string>()
-  expectTypeOf(strictDirectComposer.n(1, 'custom' as any)).toEqualTypeOf<
-    string | Intl.NumberFormatPart[]
-  >()
+  expectTypeOf(
+    strictDirectComposer.n(1, { key: 'currency', locale: 'en', part: true })
+  ).toEqualTypeOf<Intl.NumberFormatPart[]>()
 
   // const noOptionsComposer = createComposer({ missingWarn: true })
   const noOptionsComposer = createComposer({ locale: 'en' })
diff --git a/packages/vue-i18n/src/vue.d.ts b/packages/vue-i18n/src/vue.d.ts
index db1a29baa..a8143c519 100644
--- a/packages/vue-i18n/src/vue.d.ts
+++ b/packages/vue-i18n/src/vue.d.ts
@@ -31,6 +31,8 @@ import type {
   VueI18nOptions
 } from '../../vue-i18n-core/src/legacy'
 
+type IsPart<O> = O extends { part: infer P } ? P : false
+
 // --- THE CONTENT BELOW THIS LINE WILL BE APPENDED TO DTS FILE IN DIST DIRECTORY --- //
 declare module 'vue' {
   /**
@@ -674,9 +676,7 @@ declare module 'vue' {
     $d<
       value extends number | Date = number,
       Key extends string = string,
-      Return extends string | Intl.DateTimeFormatPart[] =
-        | string
-        | Intl.DateTimeFormatPart[],
+      OptionsType = DateTimeOptions<Key | ResourceKeys>,
       DefinedDateTimeFormat extends
         RemovedIndexResources<DefineDateTimeFormat> = RemovedIndexResources<DefineDateTimeFormat>,
       Keys = IsEmptyObject<DefinedDateTimeFormat> extends false
@@ -687,8 +687,8 @@ declare module 'vue' {
       ResourceKeys extends Keys = IsNever<Keys> extends false ? Keys : never
     >(
       value: number | Date,
-      options: DateTimeOptions<Key, ResourceKeys>
-    ): Return
+      options: OptionsType
+    ): IsPart<OptionsType> extends true ? Intl.DateTimeFormatPart[] : string
     /**
      * Number formatting
      *
@@ -884,9 +884,7 @@ declare module 'vue' {
      */
     $n<
       Key extends string,
-      Return extends string | Intl.NumberFormatPart[] =
-        | string
-        | Intl.NumberFormatPart[],
+      OptionsType = NumberOptions<Key | ResourceKeys>,
       DefinedNumberFormat extends
         RemovedIndexResources<DefineDateTimeFormat> = RemovedIndexResources<DefineDateTimeFormat>,
       Keys = IsEmptyObject<DefinedNumberFormat> extends false
@@ -897,8 +895,8 @@ declare module 'vue' {
       ResourceKeys extends Keys = IsNever<Keys> extends false ? Keys : never
     >(
       value: number,
-      options: NumberOptions<Key, ResourceKeys>
-    ): Return
+      options: OptionsType
+    ): IsPart<OptionsType> extends true ? Intl.NumberFormatPart[] : string
     /**
      * Locale messages getter
      *