feat: Pass props to I18nProvider.defaultComponent in Trans.render style

docs/ref/react.rst

@@ -171,6 +171,32 @@ I18nProvider
 components. :ref:`Rendering of translations <rendering-translations>` is explained
 at the beginning of this document.
 
+.. code-block:: jsx
+
+   import React from 'react';
+   import { I18nProvider } from '@lingui/react';
+   import { i18n } from '@lingui/core';
+   import { messages as messagesEn } from './locales/en/messages.js';
+
+   i18n.load({
+      en: messagesEn,
+   });
+   i18n.activate('en');
+
+   const DefaultI18n = ({ isTranslated, children }) => (
+      <span style={{ color: isTranslated ? undefined : 'red' }}>
+         {children}
+      </span>
+   )
+
+   const App = () => {
+      return (
+         <I18nProvider i18n={i18n} defaultComponent={DefaultI18n}>
+            // rest of the app
+         </I18nProvider>
+      );
+   }
+
 ``forceRenderOnLocaleChange`` is true by default and it ensures that:
 
   - Children of ``I18nProvider`` aren't rendered before locales are loaded.

packages/react/src/I18nProvider.tsx

@@ -1,9 +1,10 @@
-import React, { FunctionComponent, ComponentType, ReactNode } from "react"
+import React, { ComponentType, FunctionComponent } from "react"
 import { I18n } from "@lingui/core"
+import { TransRenderProps } from "./Trans"
 
 export type I18nContext = {
   i18n: I18n
-  defaultComponent?: ComponentType<{ children?: ReactNode }>
+  defaultComponent?: ComponentType<TransRenderProps>
 }
 
 export type withI18nProps = {

packages/react/src/Trans.test.tsx

@@ -172,6 +172,7 @@ describe("Trans component", function () {
         id: "ID",
         message: "Default",
         translation: "Translation",
+        isTranslated: true,
       })
     })
 
@@ -241,4 +242,54 @@ describe("Trans component", function () {
       expect(element).toEqual(`<div>value</div>`)
     })
   })
+
+  describe("I18nProvider defaulComponent accepts render-like props", function () {
+    const DefaultComponent: React.FunctionComponent = (props: {
+      children?: React.ReactNode
+      id: string
+      translation: string
+      message: string
+      isTranslated: boolean
+    }) => (
+      <>
+        <div data-testid="children">{props.children}</div>
+        {props.id && <div data-testid="id">{props.id}</div>}
+        {props.message && <div data-testid="message">{props.message}</div>}
+        {props.translation && (
+          <div data-testid="translation">{props.translation}</div>
+        )}
+
+        <div data-testid="is-translated">{String(props.isTranslated)}</div>
+      </>
+    )
+
+    it("should render defaultComponent with Trans props", function () {
+      const markup = render(
+        <I18nProvider i18n={i18n} defaultComponent={DefaultComponent}>
+          <Trans id="ID" message="Some message" />
+        </I18nProvider>
+      )
+
+      expect(markup.queryByTestId("id").innerHTML).toEqual("ID")
+      expect(markup.queryByTestId("message").innerHTML).toEqual("Some message")
+      expect(markup.queryByTestId("translation").innerHTML).toEqual(
+        "Translation"
+      )
+      expect(markup.queryByTestId("is-translated").innerHTML).toEqual("true")
+    })
+
+    it("should pass isTranslated: false if no translation", function () {
+      const markup = render(
+        <I18nProvider i18n={i18n} defaultComponent={DefaultComponent}>
+          <Trans id="NO_ID" message="Some message" />
+        </I18nProvider>
+      )
+
+      expect(markup.queryByTestId("id").innerHTML).toEqual("NO_ID")
+      expect(markup.queryByTestId("translation").innerHTML).toEqual(
+        "Some message"
+      )
+      expect(markup.queryByTestId("is-translated").innerHTML).toEqual("false")
+    })
+  })
 })

packages/react/src/Trans.tsx

@@ -8,6 +8,7 @@ export type TransRenderProps = {
   translation?: React.ReactNode
   children?: React.ReactNode
   message?: string | null
+  isTranslated?: boolean
 }
 
 export type TransProps = {
@@ -72,6 +73,13 @@ export function Trans(props: TransProps): React.ReactElement<any, any> | null {
   const FallbackComponent = (defaultComponent ||
     React.Fragment) as React.ComponentType<any>
 
+  const i18nProps = {
+    id,
+    message,
+    translation,
+    isTranslated: id !== translation && message !== translation,
+  }
+
   // Validation of `render` and `component` props
   if (render && component) {
     console.error(
@@ -87,22 +95,24 @@ export function Trans(props: TransProps): React.ReactElement<any, any> | null {
     console.error(
       `Invalid value supplied to prop \`component\`. It must be a React component, provided ${component}`
     )
-    return <FallbackComponent>{translation}</FallbackComponent>
+    return <FallbackComponent {...i18nProps}>{translation}</FallbackComponent>
   }
 
   // Rendering using a render prop
   if (typeof render === "function") {
     // Component: render={(props) => <a title={props.translation}>x</a>}
-    return render({
-      id,
-      translation,
-      message,
-    })
+    return render(i18nProps)
   }
 
   // `component` prop has a higher precedence over `defaultComponent`
   const Component = (component || FallbackComponent) as React.ComponentType<any>
-  return <Component>{translation}</Component>
+  const DefaultComponent = defaultComponent
+
+  return DefaultComponent && !component ? (
+    <DefaultComponent {...i18nProps}>{translation}</DefaultComponent>
+  ) : (
+    <Component>{translation}</Component>
+  )
 }
 
 Trans.defaultProps = {