Add type safety for getT function (#1184)

* Update type-safety.md * Update next-translate.d.ts with new TranslateFunction interface * Refactor translation types in next-translate.d.ts * Refactor type safety in TranslateFunction
aralroca · Apr 8, 2024 · b63006f · b63006f
1 parent 4f74c0d
commit b63006f
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diff --git a/docs/type-safety.md b/docs/type-safety.md
@@ -14,22 +14,32 @@ export interface TranslationsKeys {
  // Specify here all the namespaces you have...
 }
 
-export interface TypeSafeTranslate<Namespace extends keyof TranslationsKeys>
+type TranslationNamespace = keyof TranslationsKeys;
+
+export interface TranslateFunction<Namespace extends TranslationNamespace> {
+ (
+ key: TranslationsKeys[Namespace],
+ ...rest: Tail<Parameters<Translate>>
+ ): string
+ <T extends string>(template: TemplateStringsArray): string
+};
+
+export interface TypeSafeTranslate<Namespace extends TranslationNamespace>
  extends Omit<I18n, 't'> {
- t: {
- (
- key: TranslationsKeys[Namespace],
- ...rest: Tail<Parameters<Translate>>
- ): string
- <T extends string>(template: TemplateStringsArray): string
- }
+ t: TranslateFunction<Namespace>
 }
 
 declare module 'next-translate/useTranslation' {
  export default function useTranslation<
- Namespace extends keyof TranslationsKeys
+ Namespace extends TranslationNamespace
  >(namespace: Namespace): TypeSafeTranslate<Namespace>
 }
+
+declare module 'next-translate/getT' {
+ export default function getT<
+ Namespace extends TranslationNamespace
+ >(locale?: string, namespace: Namespace): Promise<TranslateFunction<Namespace>> 
+}
 ```
 
 Then type safety should work:
@@ -38,4 +48,4 @@ Then type safety should work:
 
 <img width="282" alt="Screenshot 2023-07-17 at 19 22 00" src="https://github.com/aralroca/next-translate/assets/13313058/616987b4-e49b-4cf2-b511-cdfaba57e1d2">
 
-Reference: https://github.com/aralroca/next-translate/pull/1108
+Reference: <https://github.com/aralroca/next-translate/pull/1108>
diff --git a/examples/with-app-directory/next-translate.d.ts b/examples/with-app-directory/next-translate.d.ts
@@ -1,23 +1,37 @@
 import type { Paths, I18n, Translate } from 'next-translate'
 
+type Tail<T> = T extends [unknown, ...infer Rest] ? Rest : never;
+
 export interface TranslationsKeys {
+ // Example with "common" and "home" namespaces in "en" (the default language):
  common: Paths<typeof import('./locales/en/common.json')>
  home: Paths<typeof import('./locales/en/home.json')>
+ // Specify here all the namespaces you have...
 }
 
-export interface TypeSafeTranslate<Namespace extends keyof TranslationsKeys>
+type TranslationNamespace = keyof TranslationsKeys;
+
+export interface TranslateFunction<Namespace extends TranslationNamespace> {
+ (
+ key: TranslationsKeys[Namespace],
+ ...rest: Tail<Parameters<Translate>>
+ ): string
+ <T extends string>(template: TemplateStringsArray): string
+};
+
+export interface TypeSafeTranslate<Namespace extends TranslationNamespace>
  extends Omit<I18n, 't'> {
- t: {
- (
- key: TranslationsKeys[Namespace],
- ...rest: Tail<Parameters<Translate>>
- ): string
- <T extends string>(template: TemplateStringsArray): string
- }
+ t: TranslateFunction<Namespace>
 }
 
 declare module 'next-translate/useTranslation' {
  export default function useTranslation<
- Namespace extends keyof TranslationsKeys
+ Namespace extends TranslationNamespace
  >(namespace: Namespace): TypeSafeTranslate<Namespace>
 }
+
+declare module 'next-translate/getT' {
+ export default function getT<
+ Namespace extends TranslationNamespace
+ >(locale?: string, namespace: Namespace): Promise<TranslateFunction<Namespace>> 
+}