feat(role-manager): add error toast notification on dashboard refresh failure

- Update useDashboardData refetch to propagate errors using Promise.allSettled
- Add handleRefresh wrapper in Dashboard to catch errors and show toast
- Add 3 test cases for refetch error propagation behavior

Author: pasevin

apps/role-manager/src/hooks/__tests__/useDashboardData.test.tsx

@@ -295,6 +295,102 @@ describe('useDashboardData', () => {
       expect(mockRolesRefetch).toHaveBeenCalledTimes(1);
       expect(mockOwnershipRefetch).toHaveBeenCalledTimes(1);
     });
+
+    it('throws error when roles refetch fails', async () => {
+      const mockRolesRefetch = vi.fn().mockRejectedValue(new Error('Network error'));
+      const mockOwnershipRefetch = vi.fn().mockResolvedValue(undefined);
+
+      vi.mocked(useContractDataModule.useContractRoles).mockReturnValue({
+        roles: [],
+        isLoading: false,
+        error: null,
+        refetch: mockRolesRefetch,
+        isEmpty: true,
+        totalMemberCount: 0,
+        canRetry: false,
+        errorMessage: null,
+        hasError: false,
+      });
+
+      vi.mocked(useContractDataModule.useContractOwnership).mockReturnValue({
+        ownership: null,
+        isLoading: false,
+        error: null,
+        refetch: mockOwnershipRefetch,
+        hasOwner: false,
+        canRetry: false,
+        errorMessage: null,
+        hasError: false,
+      });
+
+      const { result } = renderHook(() => useDashboardData(mockAdapter, testAddress), { wrapper });
+
+      await expect(result.current.refetch()).rejects.toThrow('Network error');
+    });
+
+    it('throws error when ownership refetch fails', async () => {
+      const mockRolesRefetch = vi.fn().mockResolvedValue(undefined);
+      const mockOwnershipRefetch = vi.fn().mockRejectedValue(new Error('Failed to load ownership'));
+
+      vi.mocked(useContractDataModule.useContractRoles).mockReturnValue({
+        roles: [],
+        isLoading: false,
+        error: null,
+        refetch: mockRolesRefetch,
+        isEmpty: true,
+        totalMemberCount: 0,
+        canRetry: false,
+        errorMessage: null,
+        hasError: false,
+      });
+
+      vi.mocked(useContractDataModule.useContractOwnership).mockReturnValue({
+        ownership: null,
+        isLoading: false,
+        error: null,
+        refetch: mockOwnershipRefetch,
+        hasOwner: false,
+        canRetry: false,
+        errorMessage: null,
+        hasError: false,
+      });
+
+      const { result } = renderHook(() => useDashboardData(mockAdapter, testAddress), { wrapper });
+
+      await expect(result.current.refetch()).rejects.toThrow('Failed to load ownership');
+    });
+
+    it('throws with generic message when error is not an Error instance', async () => {
+      const mockRolesRefetch = vi.fn().mockRejectedValue('string error');
+      const mockOwnershipRefetch = vi.fn().mockResolvedValue(undefined);
+
+      vi.mocked(useContractDataModule.useContractRoles).mockReturnValue({
+        roles: [],
+        isLoading: false,
+        error: null,
+        refetch: mockRolesRefetch,
+        isEmpty: true,
+        totalMemberCount: 0,
+        canRetry: false,
+        errorMessage: null,
+        hasError: false,
+      });
+
+      vi.mocked(useContractDataModule.useContractOwnership).mockReturnValue({
+        ownership: null,
+        isLoading: false,
+        error: null,
+        refetch: mockOwnershipRefetch,
+        hasOwner: false,
+        canRetry: false,
+        errorMessage: null,
+        hasError: false,
+      });
+
+      const { result } = renderHook(() => useDashboardData(mockAdapter, testAddress), { wrapper });
+
+      await expect(result.current.refetch()).rejects.toThrow('Failed to refresh data');
+    });
   });
 
   describe('capability detection', () => {

apps/role-manager/src/hooks/useDashboardData.ts

@@ -124,10 +124,23 @@ export function useDashboardData(
   const canRetry = rolesCanRetry || ownershipCanRetry;
 
   // Combined refetch function - refetches both in parallel
+  // Throws on error to allow caller to handle (e.g., show toast notification)
   const refetch = useCallback(async (): Promise<void> => {
     setIsRefreshing(true);
     try {
-      await Promise.all([rolesRefetch(), ownershipRefetch()]);
+      const results = await Promise.allSettled([rolesRefetch(), ownershipRefetch()]);
+      // Check if any refetch failed and throw an aggregated error
+      const failures = results.filter(
+        (result): result is PromiseRejectedResult => result.status === 'rejected'
+      );
+      if (failures.length > 0) {
+        // Throw the first error message to signal refresh failed
+        const errorMessage =
+          failures[0].reason instanceof Error
+            ? failures[0].reason.message
+            : 'Failed to refresh data';
+        throw new Error(errorMessage);
+      }
     } finally {
       setIsRefreshing(false);
     }

apps/role-manager/src/pages/Dashboard.tsx

@@ -13,6 +13,8 @@
  */
 
 import { Download, Loader2, RefreshCw, Shield, Users } from 'lucide-react';
+import { toast } from 'sonner';
+import { useCallback } from 'react';
 import { useNavigate } from 'react-router-dom';
 
 import { Button } from '@openzeppelin/ui-builder-ui';
@@ -54,6 +56,16 @@ export function Dashboard() {
   // Determine if buttons should be disabled
   const actionsDisabled = !hasContract || isLoading || isRefreshing;
 
+  // Handle refresh with toast notification on error
+  const handleRefresh = useCallback(async () => {
+    try {
+      await refetch();
+    } catch (error) {
+      const message = error instanceof Error ? error.message : 'Failed to refresh data';
+      toast.error(`Refresh failed: ${message}`);
+    }
+  }, [refetch]);
+
   // Combined loading state for stats cards (initial load OR manual refresh)
   const isDataLoading = isLoading || isRefreshing;
 
@@ -80,7 +92,7 @@ export function Dashboard() {
             <Button
               variant="outline"
               size="sm"
-              onClick={() => refetch()}
+              onClick={handleRefresh}
               disabled={actionsDisabled}
               className="bg-white"
             >

specs/007-dashboard-real-data/tasks.md

@@ -109,7 +109,7 @@
 - [x] T025 [US3] Add refetch function to useDashboardData hook: combine rolesRefetch and ownershipRefetch with Promise.all per research.md §7
 - [x] T026 [US3] Add isRefreshing state to useDashboardData to distinguish initial load from manual refresh
 - [x] T027 [US3] Update Dashboard.tsx Refresh Data button: connect onClick to refetch, show loading indicator when isRefreshing, disable during refresh per FR-012
-- [ ] T028 [US3] Add error toast notification when refresh fails per User Story 3 acceptance scenario 3
+- [x] T028 [US3] Add error toast notification when refresh fails per User Story 3 acceptance scenario 3
 
 **Checkpoint**: Refresh Data button works, shows loading state, handles errors gracefully