fix(ui): fix library selection state for single-library users (#4686)

* fix: validate library selection state for single-library users

Fixes issues where users with a single library see no content when
selectedLibraries in localStorage contains library IDs they no longer
have access to (e.g., after removing libraries or switching accounts).

Changes:
- libraryReducer: Validate selectedLibraries when SET_USER_LIBRARIES
  is dispatched, filtering out invalid IDs and resetting to empty for
  single-library users (empty means 'all accessible libraries')
- wrapperDataProvider: Add defensive validation in getSelectedLibraries
  to check against current user libraries before applying filters
- Add comprehensive test coverage for reducer validation logic

Fixes #4553, #4508, #4569

* style: format code with prettier

ui/src/dataProvider/wrapperDataProvider.js

@@ -12,7 +12,21 @@ const isAdmin = () => {
 const getSelectedLibraries = () => {
   try {
     const state = JSON.parse(localStorage.getItem('state'))
-    return state?.library?.selectedLibraries || []
+    const selectedLibraries = state?.library?.selectedLibraries || []
+    const userLibraries = state?.library?.userLibraries || []
+
+    // Validate selected libraries against current user libraries
+    const userLibraryIds = userLibraries.map((lib) => lib.id)
+    const validatedSelection = selectedLibraries.filter((id) =>
+      userLibraryIds.includes(id),
+    )
+
+    // If user has only one library, return empty array (no filter needed)
+    if (userLibraryIds.length === 1) {
+      return []
+    }
+
+    return validatedSelection
   } catch (err) {
     return []
   }

ui/src/reducers/libraryReducer.js

@@ -8,18 +8,39 @@ const initialState = {
 export const libraryReducer = (previousState = initialState, payload) => {
   const { type, data } = payload
   switch (type) {
-    case SET_USER_LIBRARIES:
+    case SET_USER_LIBRARIES: {
+      const newUserLibraryIds = data.map((lib) => lib.id)
+
+      // Validate and filter selected libraries to only include IDs that exist in new user libraries
+      const validatedSelection = previousState.selectedLibraries.filter((id) =>
+        newUserLibraryIds.includes(id),
+      )
+
+      // Determine the final selection:
+      // 1. If first time setting libraries (no previous user libraries), select all
+      // 2. If user now has only one library, reset to empty (no filter needed)
+      // 3. Otherwise, use validated selection (may be empty if all previous selections were invalid)
+      let finalSelection
+      if (
+        previousState.selectedLibraries.length === 0 &&
+        previousState.userLibraries.length === 0
+      ) {
+        // First time: select all libraries
+        finalSelection = newUserLibraryIds
+      } else if (newUserLibraryIds.length === 1) {
+        // Single library: reset selection (empty means "all accessible")
+        finalSelection = []
+      } else {
+        // Multiple libraries: use validated selection
+        finalSelection = validatedSelection
+      }
+
       return {
         ...previousState,
         userLibraries: data,
-        // If this is the first time setting user libraries and no selection exists,
-        // default to all libraries
-        selectedLibraries:
-          previousState.selectedLibraries.length === 0 &&
-          previousState.userLibraries.length === 0
-            ? data.map((lib) => lib.id)
-            : previousState.selectedLibraries,
+        selectedLibraries: finalSelection,
       }
+    }
     case SET_SELECTED_LIBRARIES:
       return {
         ...previousState,

ui/src/reducers/libraryReducer.test.js

@@ -0,0 +1,186 @@
+import { describe, it, expect } from 'vitest'
+import { libraryReducer } from './libraryReducer'
+import { SET_SELECTED_LIBRARIES, SET_USER_LIBRARIES } from '../actions'
+
+describe('libraryReducer', () => {
+  const mockLibraries = [
+    { id: '1', name: 'Music Library' },
+    { id: '2', name: 'Podcasts' },
+    { id: '3', name: 'Audiobooks' },
+  ]
+
+  const initialState = {
+    userLibraries: [],
+    selectedLibraries: [],
+  }
+
+  describe('SET_USER_LIBRARIES', () => {
+    it('should set user libraries and select all on first load', () => {
+      const action = {
+        type: SET_USER_LIBRARIES,
+        data: mockLibraries,
+      }
+
+      const result = libraryReducer(initialState, action)
+
+      expect(result.userLibraries).toEqual(mockLibraries)
+      expect(result.selectedLibraries).toEqual(['1', '2', '3'])
+    })
+
+    it('should reset selection to empty when user has only one library', () => {
+      const previousState = {
+        userLibraries: mockLibraries,
+        selectedLibraries: ['1', '2'],
+      }
+
+      const action = {
+        type: SET_USER_LIBRARIES,
+        data: [mockLibraries[0]], // Only one library now
+      }
+
+      const result = libraryReducer(previousState, action)
+
+      expect(result.userLibraries).toEqual([mockLibraries[0]])
+      expect(result.selectedLibraries).toEqual([]) // Reset for single library
+    })
+
+    it('should filter out invalid library IDs from selection', () => {
+      const previousState = {
+        userLibraries: mockLibraries,
+        selectedLibraries: ['1', '2', '3'],
+      }
+
+      const action = {
+        type: SET_USER_LIBRARIES,
+        data: [mockLibraries[0], mockLibraries[1]], // Only libraries 1 and 2 remain
+      }
+
+      const result = libraryReducer(previousState, action)
+
+      expect(result.userLibraries).toEqual([mockLibraries[0], mockLibraries[1]])
+      expect(result.selectedLibraries).toEqual(['1', '2']) // Library 3 removed
+    })
+
+    it('should keep valid selection when libraries change', () => {
+      const previousState = {
+        userLibraries: mockLibraries,
+        selectedLibraries: ['1'],
+      }
+
+      const action = {
+        type: SET_USER_LIBRARIES,
+        data: mockLibraries, // Same libraries
+      }
+
+      const result = libraryReducer(previousState, action)
+
+      expect(result.userLibraries).toEqual(mockLibraries)
+      expect(result.selectedLibraries).toEqual(['1']) // Selection preserved
+    })
+
+    it('should handle selection becoming empty after filtering invalid IDs', () => {
+      const previousState = {
+        userLibraries: mockLibraries,
+        selectedLibraries: ['1', '2'],
+      }
+
+      const newLibraries = [{ id: '4', name: 'New Library' }]
+      const action = {
+        type: SET_USER_LIBRARIES,
+        data: newLibraries,
+      }
+
+      const result = libraryReducer(previousState, action)
+
+      expect(result.userLibraries).toEqual(newLibraries)
+      expect(result.selectedLibraries).toEqual([]) // All selected IDs were invalid
+    })
+
+    it('should handle transition from multiple to single library with invalid selection', () => {
+      const previousState = {
+        userLibraries: mockLibraries,
+        selectedLibraries: ['2', '3'], // User had libraries 2 and 3 selected
+      }
+
+      const action = {
+        type: SET_USER_LIBRARIES,
+        data: [mockLibraries[0]], // Now only has access to library 1
+      }
+
+      const result = libraryReducer(previousState, action)
+
+      expect(result.userLibraries).toEqual([mockLibraries[0]])
+      expect(result.selectedLibraries).toEqual([]) // Reset for single library
+    })
+
+    it('should handle empty library list', () => {
+      const previousState = {
+        userLibraries: mockLibraries,
+        selectedLibraries: ['1', '2'],
+      }
+
+      const action = {
+        type: SET_USER_LIBRARIES,
+        data: [],
+      }
+
+      const result = libraryReducer(previousState, action)
+
+      expect(result.userLibraries).toEqual([])
+      expect(result.selectedLibraries).toEqual([]) // All selections filtered out
+    })
+  })
+
+  describe('SET_SELECTED_LIBRARIES', () => {
+    it('should update selected libraries', () => {
+      const previousState = {
+        userLibraries: mockLibraries,
+        selectedLibraries: ['1'],
+      }
+
+      const action = {
+        type: SET_SELECTED_LIBRARIES,
+        data: ['2', '3'],
+      }
+
+      const result = libraryReducer(previousState, action)
+
+      expect(result.selectedLibraries).toEqual(['2', '3'])
+      expect(result.userLibraries).toEqual(mockLibraries) // Unchanged
+    })
+
+    it('should allow setting empty selection', () => {
+      const previousState = {
+        userLibraries: mockLibraries,
+        selectedLibraries: ['1', '2'],
+      }
+
+      const action = {
+        type: SET_SELECTED_LIBRARIES,
+        data: [],
+      }
+
+      const result = libraryReducer(previousState, action)
+
+      expect(result.selectedLibraries).toEqual([])
+    })
+  })
+
+  describe('unknown action', () => {
+    it('should return previous state for unknown action', () => {
+      const previousState = {
+        userLibraries: mockLibraries,
+        selectedLibraries: ['1'],
+      }
+
+      const action = {
+        type: 'UNKNOWN_ACTION',
+        data: null,
+      }
+
+      const result = libraryReducer(previousState, action)
+
+      expect(result).toBe(previousState) // Same reference
+    })
+  })
+})