Add type-safe support to keyPrefix option (#1390)

i18next · Oct 28, 2021 · 008d1b0 · 008d1b0
1 parent 791957d
commit 008d1b0
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Showing 3 changed files with 55 additions and 14 deletions.
diff --git a/test/typescript/custom-types/custom-types.d.ts b/test/typescript/custom-types/custom-types.d.ts
@@ -10,6 +10,9 @@ declare module 'react-i18next' {
       };
       alternate: {
         baz: 'baz';
+        foobar: {
+          barfoo: 'barfoo';
+        };
       };
     };
   }

diff --git a/test/typescript/custom-types/useTranslation.test.tsx b/test/typescript/custom-types/useTranslation.test.tsx
@@ -38,6 +38,11 @@ function readonlyArrayNamespace() {
   );
 }
 
+function keyPrefixOption() {
+  const [t] = useTranslation('alternate', { keyPrefix: 'foobar' });
+  return <>{t('barfoo')}</>;
+}
+
 function expectErrorWhenNamespaceDoesNotExist() {
   // @ts-expect-error
   const [t] = useTranslation('fake');
@@ -61,3 +66,15 @@ function expectErrorWhenUsingArrayNamespaceAndWrongKey() {
   // @ts-expect-error
   return <>{t('custom:fake')}</>;
 }
+
+function expectErrorWhenUsingWrongKeyPrefixOption() {
+  // @ts-expect-error
+  const [t] = useTranslation('alternate', { keyPrefix: 'abc' });
+  return <>{t('barfoo')}</>;
+}
+
+function expectErrorWhenUsingRightKeyPrefixOptionAndWrongKey() {
+  const [t] = useTranslation('alternate', { keyPrefix: 'foobar' });
+  // @ts-expect-error
+  return <>{t('abc')}</>;
+}
diff --git a/ts4.1/index.d.ts b/ts4.1/index.d.ts
@@ -149,12 +149,20 @@ type NormalizeMultiReturn<T, V> = V extends `${infer N}:${infer R}`
     : never
   : never;
 
-export type TFuncKey<N extends Namespace = DefaultNamespace, T = DefaultResources> = N extends
-  | (keyof T)[]
-  | Readonly<(keyof T)[]>
+type KeyPrefix<N extends Namespace> = N extends keyof DefaultResources
+  ? Fallback<string, keyof DefaultResources[N]> | undefined
+  : string | undefined;
+
+export type TFuncKey<
+  N extends Namespace = DefaultNamespace,
+  TKPrefix extends KeyPrefix<N> = undefined,
+  T = DefaultResources
+> = N extends (keyof T)[] | Readonly<(keyof T)[]>
   ? NormalizeMulti<T, N[number]>
   : N extends keyof T
-  ? Normalize<T[N]>
+  ? TKPrefix extends keyof T[N]
+    ? Normalize<T[N][TKPrefix]>
+    : Normalize<T[N]>
   : string;
 
 export type TFuncReturn<N, TKeys, TDefaultResult, T = DefaultResources> = N extends (keyof T)[]
@@ -163,17 +171,20 @@ export type TFuncReturn<N, TKeys, TDefaultResult, T = DefaultResources> = N exte
   ? NormalizeReturn<T[N], TKeys>
   : Fallback<TDefaultResult>;
 
-export interface TFunction<N extends Namespace = DefaultNamespace> {
+export interface TFunction<
+  N extends Namespace = DefaultNamespace,
+  TKPrefix extends KeyPrefix<N> = undefined
+> {
   <
-    TKeys extends TFuncKey<N> | TemplateStringsArray extends infer A ? A : never,
+    TKeys extends TFuncKey<N, TKPrefix> | TemplateStringsArray extends infer A ? A : never,
     TDefaultResult extends TFunctionResult = string,
     TInterpolationMap extends object = StringMap
   >(
     key: TKeys | TKeys[],
     options?: TOptions<TInterpolationMap> | string,
   ): TFuncReturn<N, TKeys, TDefaultResult>;
   <
-    TKeys extends TFuncKey<N> | TemplateStringsArray extends infer A ? A : never,
+    TKeys extends TFuncKey<N, TKPrefix> | TemplateStringsArray extends infer A ? A : never,
     TDefaultResult extends TFunctionResult = string,
     TInterpolationMap extends object = StringMap
   >(
@@ -208,22 +219,32 @@ export function Trans<
 
 export function useSSR(initialI18nStore: Resource, initialLanguage: string): void;
 
-export interface UseTranslationOptions {
+export interface UseTranslationOptions<
+  N extends Namespace = DefaultNamespace,
+  TKPrefix extends KeyPrefix<N> = undefined
+> {
   i18n?: i18n;
   useSuspense?: boolean;
-  keyPrefix?: string;
+  keyPrefix?: TKPrefix;
 }
 
-type UseTranslationResponse<N extends Namespace> = [TFunction<N>, i18n, boolean] & {
-  t: TFunction<N>;
+type UseTranslationResponse<N extends Namespace, TKPrefix extends KeyPrefix<N>> = [
+  TFunction<N, TKPrefix>,
+  i18n,
+  boolean,
+] & {
+  t: TFunction<N, TKPrefix>;
   i18n: i18n;
   ready: boolean;
 };
 
-export function useTranslation<N extends Namespace = DefaultNamespace>(
+export function useTranslation<
+  N extends Namespace = DefaultNamespace,
+  TKPrefix extends KeyPrefix<N> = undefined
+>(
   ns?: N | Readonly<N>,
-  options?: UseTranslationOptions,
-): UseTranslationResponse<N>;
+  options?: UseTranslationOptions<N, TKPrefix>,
+): UseTranslationResponse<N, TKPrefix>;
 
 // Need to see usage to improve this
 export function withSSR(): <Props>(