Add offline support to <ShowBase> and <Show>

docs/Show.md

@@ -70,6 +70,7 @@ That's enough to display the post show view above.
 | `disable Authentication` | Optional | `boolean` |         | Set to `true` to disable the authentication check
 | `empty WhileLoading` | Optional | `boolean`     |         | Set to `true` to return `null` while the show is loading
 | `id`             | Optional | `string | number` |         | The record id. If not provided, it will be deduced from the URL
+| `offline`        | Optional | `ReactNode`       |         | The component to render when there is no connectivity and the record isn't in the cache
 | `queryOptions`   | Optional | `object`          |         | The options to pass to the `useQuery` hook
 | `resource`       | Optional | `string`          |         | The resource name, e.g. `posts`
 | `sx`             | Optional | `object`          |         | Override or extend the styles applied to the component
@@ -83,7 +84,7 @@ By default, `<Show>` includes an action toolbar with an `<EditButton>` if the `<
 
 ```jsx
 import Button from '@mui/material/Button';
-import { EditButton, TopToolbar } from 'react-admin';
+import { EditButton, Show, TopToolbar } from 'react-admin';
 
 const PostShowActions = () => (
     <TopToolbar>
@@ -158,6 +159,8 @@ React-admin provides 2 built-in show layout components:
 To use an alternative layout, switch the `<Show>` child component:
 
 ```diff
+import { Show } from 'react-admin';
+
 export const PostShow = () => (
     <Show>
 -       <SimpleShowLayout>
@@ -188,6 +191,7 @@ You can override the main area container by passing a `component` prop:
 
 {% raw %}
 ```jsx
+import { Show } from 'react-admin';
 import { Box } from '@mui/material';
 
 const ShowWrapper = ({ children }) => (
@@ -210,6 +214,8 @@ const PostShow = () => (
 By default, the `<Show>` component will automatically redirect the user to the login page if the user is not authenticated. If you want to disable this behavior and allow anonymous access to a show page, set the `disableAuthentication` prop to `true`.
 
 ```jsx
+import { Show } from 'react-admin';
+
 const PostShow = () => (
     <Show disableAuthentication>
         ...
@@ -273,6 +279,8 @@ const BookShow = () => (
 By default, `<Show>` deduces the identifier of the record to show from the URL path. So under the `/posts/123/show` path, the `id` prop will be `123`. You may want to force a different identifier. In this case, pass a custom `id` prop.
 
 ```jsx
+import { Show } from 'react-admin';
+
 export const PostShow = () => (
     <Show id="123">
         ...
@@ -282,6 +290,35 @@ export const PostShow = () => (
 
 **Tip**: Pass both a custom `id` and a custom `resource` prop to use `<Show>` independently of the current URL. This even allows you to use more than one `<Show>` component in the same page.
 
+## `offline`
+
+By default, `<Show>` renders the `<Offline>` component when there is no connectivity and the record hasn't been cached yet. You can provide your own component via the `offline` prop:
+
+```jsx
+import { Show } from 'react-admin';
+
+export const PostShow = () => (
+    <Show offline={<p>No network. Could not load the post.</p>}>
+        ...
+    </Show>
+);
+```
+
+**Tip**: If the record is in the Tanstack Query cache but you want to warn the user that they may see an outdated version, you can use the `<IsOffline>` component:
+
+```jsx
+import { Show, IsOffline } from 'react-admin';
+
+export const PostShow = () => (
+    <Show offline={<p>No network. Could not load the post.</p>}>
+        <IsOffline>
+            No network. The post data may be outdated.
+        </IsOffline>
+        ...
+    </Show>
+);
+```
+
 ## `queryOptions`
 
 `<Show>` accepts a `queryOptions` prop to pass options to the react-query client. 
@@ -372,6 +409,8 @@ export const PostShow = () => (
 By default, `<Show>` operates on the current `ResourceContext` (defined at the routing level), so under the `/posts/1/show` path, the `resource` prop will be `posts`. You may want to force a different resource. In this case, pass a custom `resource` prop, and it will override the `ResourceContext` value.
 
 ```jsx
+import { Show } from 'react-admin';
+
 export const UsersShow = () => (
     <Show resource="users">
         ...

docs/ShowBase.md

@@ -63,10 +63,11 @@ const App = () => (
 | Prop             | Required | Type              | Default | Description
 |------------------|----------|-------------------|---------|--------------------------------------------------------
 | `children`       | Optional | `ReactNode`       |         | The components rendering the record fields
-| `render`       | Optional | `(props: ShowControllerResult<RecordType>) => ReactNode`       |         | Alternative to children, a function that takes the ShowController context and renders the form
+| `render`         | Optional | `(props: ShowControllerResult<RecordType>) => ReactNode`       |         | Alternative to children, a function that takes the ShowController context and renders the form
 | `disable Authentication` | Optional | `boolean` |         | Set to `true` to disable the authentication check
-| `empty WhileLoading` | Optional | `boolean`     |         | Set to `true` to return `null` while the list is loading
 | `id`             | Optional | `string`          |         | The record identifier. If not provided, it will be deduced from the URL
+| `loading`        | Optional | `ReactNode`       |         | The component to render while checking for authentication and permissions
+| `offline`        | Optional | `ReactNode`       |         | The component to render when there is no connectivity and the record isn't in the cache
 | `queryOptions`   | Optional | `object`          |         | The options to pass to the `useQuery` hook
 | `resource`       | Optional | `string`          |         | The resource name, e.g. `posts`
 
@@ -107,38 +108,13 @@ const BookShow = () => (
 ```
 {% endraw %}
 
-## `render`
-
-Alternatively, you can pass a `render` function prop instead of children. This function will receive the `ShowContext` as argument. 
-
-{% raw %}
-```jsx
-import { ShowBase, TextField, DateField, ReferenceField, WithRecord } from 'react-admin';
-
-const BookShow = () => (
-    <ShowBase render={({ isPending, error, record }) => {
-        if (isPending) {
-            return <p>Loading...</p>;
-        }
-
-        if (error) {
-            return (
-                <p className="error">
-                    {error.message}
-                </p>
-            );
-        }
-        return <p>{record.title}</p>;
-    }}/>
-);
-```
-{% endraw %}
-
 ## `disableAuthentication`
 
 By default, the `<ShowBase>` component will automatically redirect the user to the login page if the user is not authenticated. If you want to disable this behavior and allow anonymous access to a show page, set the `disableAuthentication` prop to `true`.
 
 ```jsx
+import { ShowBase } from 'ra-core';
+
 const PostShow = () => (
     <ShowBase disableAuthentication>
         ...
@@ -151,6 +127,8 @@ const PostShow = () => (
 By default, `<ShowBase>` deduces the identifier of the record to show from the URL path. So under the `/posts/123/show` path, the `id` prop will be `123`. You may want to force a different identifier. In this case, pass a custom `id` prop.
 
 ```jsx
+import { ShowBase } from 'ra-core';
+
 export const PostShow = () => (
     <ShowBase id="123">
         ...
@@ -160,6 +138,49 @@ export const PostShow = () => (
 
 **Tip**: Pass both a custom `id` and a custom `resource` prop to use `<ShowBase>` independently of the current URL. This even allows you to use more than one `<ShowBase>` component in the same page.
 
+## `loading`
+
+By default, `<ShowBase>` renders nothing while checking for authentication and permissions. You can provide your own component via the `loading` prop:
+
+```jsx
+import { ShowBase } from 'ra-core';
+
+export const PostShow = () => (
+    <ShowBase loading={<p>Checking for permissions...</p>}>
+        ...
+    </ShowBase>
+);
+```
+
+## `offline`
+
+By default, `<ShowBase>` renders nothing when there is no connectivity and the record hasn't been cached yet. You can provide your own component via the `offline` prop:
+
+```jsx
+import { ShowBase } from 'ra-core';
+
+export const PostShow = () => (
+    <ShowBase offline={<p>No network. Could not load the post.</p>}>
+        ...
+    </ShowBase>
+);
+```
+
+**Tip**: If the record is in the Tanstack Query cache but you want to warn the user that they may see an outdated version, you can use the `<IsOffline>` component:
+
+```jsx
+import { ShowBase, IsOffline } from 'ra-core';
+
+export const PostShow = () => (
+    <ShowBase offline={<p>No network. Could not load the post.</p>}>
+        <IsOffline>
+            No network. The post data may be outdated.
+        </IsOffline>
+        ...
+    </ShowBase>
+);
+```
+
 ## `queryOptions`
 
 `<ShowBase>` accepts a `queryOptions` prop to pass options to the react-query client. 
@@ -205,11 +226,40 @@ The default `onError` function is:
 }
 ```
 
+## `render`
+
+Alternatively, you can pass a `render` function prop instead of children. This function will receive the `ShowContext` as argument. 
+
+{% raw %}
+```jsx
+import { ShowBase, TextField, DateField, ReferenceField, WithRecord } from 'react-admin';
+
+const BookShow = () => (
+    <ShowBase render={({ isPending, error, record }) => {
+        if (isPending) {
+            return <p>Loading...</p>;
+        }
+
+        if (error) {
+            return (
+                <p className="error">
+                    {error.message}
+                </p>
+            );
+        }
+        return <p>{record.title}</p>;
+    }}/>
+);
+```
+{% endraw %}
+
 ## `resource`
 
 By default, `<ShowBase>` operates on the current `ResourceContext` (defined at the routing level), so under the `/posts/1/show` path, the `resource` prop will be `posts`. You may want to force a different resource. In this case, pass a custom `resource` prop, and it will override the `ResourceContext` value.
 
 ```jsx
+import { ShowBase } from 'ra-core';
+
 export const UsersShow = () => (
     <ShowBase resource="users">
         ...

packages/ra-core/src/controller/show/ShowBase.spec.tsx

@@ -7,6 +7,7 @@ import {
     AccessControl,
     DefaultTitle,
     NoAuthProvider,
+    Offline,
     WithAuthProviderNoAccessControl,
     WithRenderProp,
 } from './ShowBase.stories';
@@ -118,4 +119,16 @@ describe('ShowBase', () => {
         expect(dataProvider.getOne).toHaveBeenCalled();
         await screen.findByText('Hello');
     });
+
+    it('should render the offline prop node when offline', async () => {
+        const { rerender } = render(<Offline isOnline={false} />);
+        await screen.findByText('You are offline, cannot load data');
+        rerender(<Offline isOnline={true} />);
+        await screen.findByText('Hello');
+        expect(
+            screen.queryByText('You are offline, cannot load data')
+        ).toBeNull();
+        rerender(<Offline isOnline={false} />);
+        await screen.findByText('You are offline, the data may be outdated');
+    });
 });

packages/ra-core/src/controller/show/ShowBase.stories.tsx

@@ -2,19 +2,21 @@ import * as React from 'react';
 import englishMessages from 'ra-language-english';
 import frenchMessages from 'ra-language-french';
 import polyglotI18nProvider from 'ra-i18n-polyglot';
+import fakeRestDataProvider from 'ra-data-fakerest';
 import {
     AuthProvider,
     CoreAdminContext,
     ShowBase,
     ShowBaseProps,
     DataProvider,
-    testDataProvider,
-    useRecordContext,
     mergeTranslations,
     I18nProvider,
     useShowContext,
     useLocaleState,
+    IsOffline,
+    WithRecord,
 } from '../..';
+import { onlineManager } from '@tanstack/react-query';
 
 export default {
     title: 'ra-core/controller/ShowBase',
@@ -162,21 +164,72 @@ export const WithRenderProp = ({
     </CoreAdminContext>
 );
 
-const defaultDataProvider = testDataProvider({
-    getOne: () =>
-        // @ts-ignore
-        Promise.resolve({ data: { id: 12, test: 'Hello', title: 'Hello' } }),
-});
+export const Offline = ({
+    dataProvider = defaultDataProvider,
+    isOnline = true,
+    ...props
+}: {
+    dataProvider?: DataProvider;
+    isOnline?: boolean;
+} & Partial<ShowBaseProps>) => {
+    React.useEffect(() => {
+        onlineManager.setOnline(isOnline);
+    }, [isOnline]);
+    return (
+        <CoreAdminContext dataProvider={dataProvider}>
+            <ShowBase
+                {...defaultProps}
+                {...props}
+                offline={<p>You are offline, cannot load data</p>}
+            >
+                <OfflineChild />
+            </ShowBase>
+        </CoreAdminContext>
+    );
+};
+
+Offline.args = {
+    isOnline: true,
+};
+
+Offline.argTypes = {
+    isOnline: {
+        control: { type: 'boolean' },
+    },
+};
+
+const defaultDataProvider = fakeRestDataProvider(
+    {
+        posts: [
+            { id: 12, test: 'Hello', title: 'Hello' },
+            { id: 13, test: 'World', title: 'World' },
+        ],
+    },
+    process.env.NODE_ENV !== 'test',
+    process.env.NODE_ENV !== 'test' ? 300 : 0
+);
 
 const defaultProps = {
     id: 12,
     resource: 'posts',
 };
 
 const Child = () => {
-    const record = useRecordContext();
+    return <WithRecord render={record => <p>{record?.test}</p>} />;
+};
 
-    return <p>{record?.test}</p>;
+const OfflineChild = () => {
+    return (
+        <>
+            <p>Use the story controls to simulate offline mode:</p>
+            <IsOffline>
+                <p style={{ color: 'orange' }}>
+                    You are offline, the data may be outdated
+                </p>
+            </IsOffline>
+            <WithRecord render={record => <p>{record?.test}</p>} />
+        </>
+    );
 };
 
 const Title = () => {