Change DefaultTFuncReturn to return null if returnNull typeOpti…

…on is true (#1865) * Change DefaultTFuncReturn to return null if returnNull typeOption is true * Fix tests
i18next · Nov 12, 2022 · 95489dd · 95489dd
1 parent 26073c4
commit 95489dd
Show file tree

Hide file tree

Showing 4 changed files with 9 additions and 8 deletions.
diff --git a/index.d.ts b/index.d.ts
@@ -860,7 +860,7 @@ type NormalizeMultiReturn<T, V> = V extends `${infer N}:${infer R}`
     : never
   : never;
 
-export type DefaultTFuncReturn = string | undefined | null;
+export type DefaultTFuncReturn = string | (TypeOptions['returnNull'] extends true ? null : never);
 
 export type DefaultTFuncReturnWithObject = DefaultTFuncReturn | object | Array<string | object>;
 

diff --git a/test/typescript/custom-types/i18next.d.ts b/test/typescript/custom-types/i18next.d.ts
@@ -3,6 +3,7 @@ import 'i18next';
 declare module 'i18next' {
   interface CustomTypeOptions {
     defaultNS: 'custom';
+    returnNull: false;
     resources: {
       custom: {
         foo: 'foo';

diff --git a/test/typescript/custom-types/t.test.ts b/test/typescript/custom-types/t.test.ts
@@ -45,3 +45,10 @@ function i18nextTPluralsUsage() {
   i18next.t('plurals:foo', { count: 1 });
   i18next.t('plurals:foo_many', { count: 10 });
 }
+
+// @ts-expect-error
+function returnNullWithFalseValue(t: TFunction<string>) {
+  function fn(value: null) {}
+  // @ts-expect-error
+  fn(t('foo'));
+}
diff --git a/test/typescript/t.test.ts b/test/typescript/t.test.ts
@@ -43,13 +43,6 @@ function callsMethodWithOptionalNullArg(t: TFunction) {
   displayHint(t('friend'));
 }
 
-function callsMethodWithOptionalArg(t: TFunction) {
-  function displayHint(hint?: string) {
-    return String(hint);
-  }
-  displayHint(t('friend'));
-}
-
 function callsMethodWithRequiredNullArg(t: TFunction) {
   function displayHint(hint: string | null) {
     return String(hint);