add generic type to t function and the tests

package.json

@@ -58,7 +58,7 @@
     "eslint-plugin-jsx-a11y": "6.1.1",
     "eslint-plugin-prettier": "2.7.0",
     "eslint-plugin-react": "7.11.1",
-    "i18next": "13.1.0",
+    "i18next": "^13.1.4",
     "jest": "23.6.0",
     "jest-cli": "23.6.0",
     "mkdirp": "0.5.1",
@@ -79,7 +79,7 @@
     "yargs": "12.0.2"
   },
   "peerDependencies": {
-    "i18next": ">= 6.0.1",
+    "i18next": ">= 13.1.3",
     "react": ">= 16.3.0"
   },
   "scripts": {

src/index.d.ts

@@ -24,9 +24,8 @@ export function setI18n(instance: i18next.i18n): void
 
 export function getI18n(): i18next.i18n
 
-export interface I18nContextValues {
+export interface I18nContextValues extends i18next.WithT {
   i18n: i18next.i18n
-  t: i18next.TranslationFunction
   defaultNS?: string
   reportNS?: string
   lng?: string
@@ -74,7 +73,7 @@ export interface NamespacesConsumerProps extends ReactI18NextOptions {
   initialI18nStore?: {}
   initialLanguage?: string
   children: (
-    t: i18next.TranslationFunction,
+    t: i18next.WithT['t'],
     options: {
       i18n: i18next.i18n
       lng: string
@@ -94,12 +93,11 @@ export interface I18nextProviderProps {
 
 export const I18nextProvider: React.ComponentClass<I18nextProviderProps>
 
-export interface TransProps {
+export interface TransProps extends Partial<i18next.WithT>{
   i18nKey?: string
   count?: number
   parent?: React.ReactNode
   i18n?: i18next.i18n
-  t?: i18next.TranslationFunction
   defaults?: string
   values?: {}
   components?: React.ReactNode[]

test/typescript/GenericTlanslateFunction.test.tsx

@@ -0,0 +1,86 @@
+import * as React from "react";
+import {
+  NamespacesConsumer,
+  Trans,
+  withNamespaces,
+  WithNamespaces,
+} from 'react-i18next';
+
+type TKeys = "title" | "text";
+
+function NamespacesConsumerTest() {
+  return (
+    <NamespacesConsumer>
+      {(t, { i18n }) =>
+        <div>
+          <h2>{t<TKeys>("title")}</h2>
+          <span>{t("any")}</span>
+          <span>{t("any", {anyObject: {}})}</span>
+          <span>{t<TKeys>("text")}</span>
+          <span>{t<TKeys, {key: string}>("text", {key: "foo"})}</span>
+          <span>{t<TKeys, {key: "bar"}, string>("text", {key: "bar"})}</span>
+        </div>
+      }
+    </NamespacesConsumer>
+  );
+}
+
+function TransComponentTest({ t }: WithNamespaces) {
+  return (
+    <div>
+      <Trans i18nKey="description.part1">
+        To get started, edit <code>src/App.js</code> and save to reload.
+      </Trans>
+      <Trans i18nKey="description.part1">
+        To get started, <strong title={t<TKeys>("title")}>{{name}}</strong>and save to reload.
+      </Trans>
+    </div>
+  );
+}
+
+const MyComponentWrapped = withNamespaces()(TransComponentTest);
+
+type ArticleKeys = "article.part1" | "article.part2";
+type AnotherArticleKeys = "anotherArticle.part1" | "anotherArticle.part2";
+
+/**
+ * Overload makes completion of arguments by without specifying type parameters
+ */
+interface OverloadedWithNamespaces extends WithNamespaces {
+  t(key: ArticleKeys, b?: object): any;
+  // NOTION: disable no-unnecessary-generics for generic test
+  // tslint:disable-next-line:no-unnecessary-generics
+  t<T extends AnotherArticleKeys>(key: T, b: {name: string}): any;
+}
+
+class App extends React.Component<OverloadedWithNamespaces> {
+  render() {
+    const { t, i18n } = this.props;
+
+    const changeLanguage = (lng: string) => {
+      i18n.changeLanguage(lng);
+    };
+
+    return (
+      <div className="App">
+        <div className="App-header">
+          <NamespacesConsumerTest />
+          <button onClick={() => changeLanguage("de")}>de</button>
+          <button onClick={() => changeLanguage("en")}>en</button>
+        </div>
+        <div className="App-intro">
+          <MyComponentWrapped />
+        </div>
+        <article>
+          <div>{t("article.part1", {name: "foo"})}</div>
+          <div>{t("article.part2")}</div>
+        </article>
+        <article>
+          <div>{t<AnotherArticleKeys>("anotherArticle.part1", {name: "foo"})}</div>
+          <div>{t<AnotherArticleKeys>("anotherArticle.part2", {name: "bar"})}</div>
+        </article>
+      </div>
+    );
+  }
+}
+export default withNamespaces("translation")(App);