fix(ui): add Rescan button to plugin list empty state (#5471)

* feat(ui): add Rescan button to plugin list empty state

When no plugins are installed and the folder watcher fails to detect new
plugins, users had no way to trigger a rescan. Extract RescanButton into
a shared component and render it in a custom empty state for the plugin
list.

* refactor(ui): address review feedback for plugin empty state

- Pass label translation key directly to RA Button (auto-translates)
- Use within() from Testing Library instead of querySelector for
  scoped queries with better error messages

ui/src/plugin/PluginList.jsx

@@ -2,6 +2,7 @@ import React, { useMemo, useState, useCallback } from 'react'
 import {
   Button,
   Datagrid,
+  Empty,
   TextField,
   TopToolbar,
   useNotify,
@@ -10,7 +11,13 @@ import {
   useTranslate,
 } from 'react-admin'
 import { makeStyles } from '@material-ui/core/styles'
-import { useMediaQuery, Tooltip, Chip, Typography } from '@material-ui/core'
+import {
+  useMediaQuery,
+  Tooltip,
+  Chip,
+  Typography,
+  Box,
+} from '@material-ui/core'
 import { MdError, MdRefresh } from 'react-icons/md'
 import { List, DateField, SimpleList, useResourceRefresh } from '../common'
 import { httpClient } from '../dataProvider'
@@ -72,8 +79,7 @@ const ManifestField = ({ source }) => {
   return <Typography variant="body2">{manifest[source] || '-'}</Typography>
 }
 
-const PluginListActions = () => {
-  const translate = useTranslate()
+const RescanButton = () => {
   const notify = useNotify()
   const refresh = useRefresh()
   const [loading, setLoading] = useState(false)
@@ -92,20 +98,37 @@ const PluginListActions = () => {
       })
   }, [notify, refresh])
 
+  return (
+    <Button
+      onClick={handleRescan}
+      disabled={loading}
+      label="resources.plugin.actions.rescan"
+      data-testid="rescan-button"
+    >
+      <MdRefresh />
+    </Button>
+  )
+}
+
+const PluginListActions = () => {
   return (
     <TopToolbar>
-      <Button
-        onClick={handleRescan}
-        disabled={loading}
-        label={translate('resources.plugin.actions.rescan')}
-        data-testid="rescan-button"
-      >
-        <MdRefresh />
-      </Button>
+      <RescanButton />
     </TopToolbar>
   )
 }
 
+const PluginEmpty = () => {
+  return (
+    <>
+      <Empty />
+      <Box textAlign="center" mt={2}>
+        <RescanButton />
+      </Box>
+    </>
+  )
+}
+
 const PluginList = (props) => {
   const isXsmall = useMediaQuery((theme) => theme.breakpoints.down('xs'))
   const translate = useTranslate()
@@ -118,6 +141,7 @@ const PluginList = (props) => {
       exporter={false}
       bulkActionButtons={false}
       actions={<PluginListActions />}
+      empty={<PluginEmpty />}
     >
       {isXsmall ? (
         <SimpleList

ui/src/plugin/PluginList.test.jsx

@@ -1,5 +1,11 @@
 import React from 'react'
-import { render, screen, fireEvent, waitFor } from '@testing-library/react'
+import {
+  render,
+  screen,
+  fireEvent,
+  waitFor,
+  within,
+} from '@testing-library/react'
 import { describe, it, expect, vi, beforeEach } from 'vitest'
 
 const mockNotify = vi.fn()
@@ -34,6 +40,7 @@ vi.mock('react-admin', async () => {
     TopToolbar: ({ children }) => (
       <div data-testid="top-toolbar">{children}</div>
     ),
+    Empty: () => <div data-testid="ra-empty">No resources</div>,
     Datagrid: ({ children }) => <div data-testid="datagrid">{children}</div>,
     TextField: ({ source }) => <span data-testid={`text-${source}`} />,
   }
@@ -42,9 +49,10 @@ vi.mock('react-admin', async () => {
 // Mock common components
 vi.mock('../common', async () => {
   return {
-    List: ({ children, actions, ...props }) => (
+    List: ({ children, actions, empty, ...props }) => (
       <div data-testid="list">
         {actions}
+        {empty && <div data-testid="empty-state">{empty}</div>}
         {children}
       </div>
     ),
@@ -94,14 +102,16 @@ describe('PluginList', () => {
     expect(screen.getByTestId('datagrid')).toBeInTheDocument()
   })
 
-  it('renders the rescan button', () => {
+  it('renders the rescan button in the toolbar', () => {
     render(<PluginList />)
-    expect(screen.getByTestId('rescan-button')).toBeInTheDocument()
+    const toolbar = screen.getByTestId('top-toolbar')
+    expect(within(toolbar).getByTestId('rescan-button')).toBeInTheDocument()
   })
 
   it('calls rescan endpoint when rescan button is clicked', async () => {
     render(<PluginList />)
-    const rescanButton = screen.getByTestId('rescan-button')
+    const toolbar = screen.getByTestId('top-toolbar')
+    const rescanButton = within(toolbar).getByTestId('rescan-button')
 
     fireEvent.click(rescanButton)
 
@@ -114,7 +124,8 @@ describe('PluginList', () => {
 
   it('calls refresh after successful rescan', async () => {
     render(<PluginList />)
-    const rescanButton = screen.getByTestId('rescan-button')
+    const toolbar = screen.getByTestId('top-toolbar')
+    const rescanButton = within(toolbar).getByTestId('rescan-button')
 
     fireEvent.click(rescanButton)
 
@@ -127,7 +138,8 @@ describe('PluginList', () => {
     mockHttpClient.mockRejectedValue(new Error('Network error'))
 
     render(<PluginList />)
-    const rescanButton = screen.getByTestId('rescan-button')
+    const toolbar = screen.getByTestId('top-toolbar')
+    const rescanButton = within(toolbar).getByTestId('rescan-button')
 
     fireEvent.click(rescanButton)
 
@@ -137,4 +149,25 @@ describe('PluginList', () => {
       })
     })
   })
+
+  it('renders a rescan button in the empty state', () => {
+    render(<PluginList />)
+    const emptyState = screen.getByTestId('empty-state')
+    expect(emptyState).toBeInTheDocument()
+    expect(within(emptyState).getByTestId('rescan-button')).toBeInTheDocument()
+  })
+
+  it('empty state rescan button triggers rescan', async () => {
+    render(<PluginList />)
+    const emptyState = screen.getByTestId('empty-state')
+    const rescanButton = within(emptyState).getByTestId('rescan-button')
+
+    fireEvent.click(rescanButton)
+
+    await waitFor(() => {
+      expect(mockHttpClient).toHaveBeenCalledWith('/api/plugin/rescan', {
+        method: 'POST',
+      })
+    })
+  })
 })