Guard search snapshot data reads that crash while a search is loading

src/components/ReportActionItem/MoneyRequestView.tsx

@@ -229,7 +229,7 @@ function MoneyRequestView({
 
     // When this component is used when merging from the search page, we might not have the parent report stored in the main collection
     const [parentReportFromOnyx] = useOnyx(`${ONYXKEYS.COLLECTION.REPORT}${parentReportID}`);
-    const parentReport = parentReportFromOnyx ?? currentSearchResults?.data[`${ONYXKEYS.COLLECTION.REPORT}${parentReportID}`];
+    const parentReport = parentReportFromOnyx ?? currentSearchResults?.data?.[`${ONYXKEYS.COLLECTION.REPORT}${parentReportID}`];
     const [iouReportOwnerLogin] = usePersonalDetail(parentReport?.ownerAccountID, loginSelector);
     const [reportPolicyTags] = useOnyx(`${ONYXKEYS.COLLECTION.POLICY_TAGS}${getNonEmptyStringOnyxID(parentReport?.policyID)}`);
 

src/hooks/useMergeTransactions.ts

@@ -56,7 +56,7 @@ function getTransaction(
         return transaction;
     }
 
-    return currentSearchResults?.data[`${ONYXKEYS.COLLECTION.TRANSACTION}${transactionID}`] ?? onyxTransaction;
+    return currentSearchResults?.data?.[`${ONYXKEYS.COLLECTION.TRANSACTION}${transactionID}`] ?? onyxTransaction;
 }
 
 function useMergeTransactions({mergeTransaction}: UseMergeTransactionsProps): UseMergeTransactionsReturn {

src/pages/Search/SearchReportsMergeReports.tsx

@@ -223,7 +223,7 @@ function SearchMergeReports() {
         isLoadingOnyxData ||
         selectedReportIDs?.some((reportID) => {
             const reportKey = `${ONYXKEYS.COLLECTION.REPORT}${reportID}` as const;
-            return !allReports?.[reportKey] && !!currentSearchResults?.data[reportKey];
+            return !allReports?.[reportKey] && !!currentSearchResults?.data?.[reportKey];
         });
 
     if (!isReportMergeBetaEnabled) {

tests/unit/hooks/useMergeTransactionsTest.ts

@@ -0,0 +1,59 @@
+import {renderHook, waitFor} from '@testing-library/react-native';
+
+import useMergeTransactions from '@hooks/useMergeTransactions';
+
+import CONST from '@src/CONST';
+import ONYXKEYS from '@src/ONYXKEYS';
+import type {MergeTransaction, SearchResults} from '@src/types/onyx';
+
+import Onyx from 'react-native-onyx';
+
+import createRandomTransaction from '../../utils/collections/transaction';
+import createMock from '../../utils/createMock';
+
+let mockCurrentSearchResults: SearchResults | undefined;
+
+jest.mock('@components/Search/SearchContext', () => ({
+    useSearchQueryContext: () => ({
+        currentSearchHash: 12345,
+    }),
+    useSearchResultsContext: () => ({
+        currentSearchResults: mockCurrentSearchResults,
+    }),
+}));
+
+jest.mock('@hooks/usePolicyForMovingExpenses', () => ({
+    __esModule: true,
+    default: () => ({policyForMovingExpensesID: undefined}),
+}));
+
+describe('useMergeTransactions', () => {
+    beforeAll(() => {
+        Onyx.init({keys: ONYXKEYS});
+    });
+
+    beforeEach(async () => {
+        await Onyx.clear();
+        mockCurrentSearchResults = undefined;
+    });
+
+    it('falls back to the Onyx transactions while the search snapshot has no data yet', async () => {
+        // Given a merge started from search while the new search's snapshot only has `search` (optimistic loading state),
+        // with transactions that exist in Onyx but not in the merge draft, so the hook looks them up in the snapshot first
+        mockCurrentSearchResults = createMock<SearchResults>({search: {type: CONST.SEARCH.DATA_TYPES.EXPENSE}});
+        const onyxTransaction1 = createRandomTransaction(1);
+        const onyxTransaction2 = createRandomTransaction(2);
+        await Onyx.merge(`${ONYXKEYS.COLLECTION.TRANSACTION}1`, onyxTransaction1);
+        await Onyx.merge(`${ONYXKEYS.COLLECTION.TRANSACTION}2`, onyxTransaction2);
+        const mergeTransaction = createMock<MergeTransaction>({targetTransactionID: '1', sourceTransactionID: '2'});
+
+        // When the hook resolves the target and source transactions
+        const {result} = renderHook(() => useMergeTransactions({mergeTransaction}));
+
+        // Then it falls back to the Onyx transactions instead of throwing on the missing snapshot data
+        await waitFor(() => {
+            expect(result.current.targetTransaction).toEqual(onyxTransaction1);
+            expect(result.current.sourceTransaction).toEqual(onyxTransaction2);
+        });
+    });
+});

tests/unit/hooks/useSearchBulkActionsTest.ts

@@ -168,7 +168,7 @@ let mockSelectedTransactions: SelectedTransactions = {};
 let mockExcludedTransactions: SelectedTransactions = {};
 let mockSelectedReports: SelectedReports[] = [];
 let mockAreAllMatchingItemsSelected = false;
-let mockCurrentSearchResults: {search: {type: string}; data: Record<string, unknown>} | undefined;
+let mockCurrentSearchResults: {search: {type: string}; data?: Record<string, unknown>} | undefined;
 
 jest.mock('@components/Search/SearchContext', () => ({
     useSearchSelectionContext: () => ({
@@ -515,6 +515,35 @@ describe('useSearchBulkActions - CSV export flow', () => {
         });
     });
 
+    it('does not crash when selected reports remain while the snapshot has no data', async () => {
+        // Given a report is still selected while a new search's snapshot only has `search` (its optimistic loading state),
+        // because the selection is cleared from an effect that runs after this render
+        mockSelectedTransactions = {tx1: makeSelectedTransaction({reportID: 'report1'})};
+        mockSelectedReports = [
+            {
+                reportID: 'report1',
+                policyID: 'policy1',
+                action: CONST.SEARCH.ACTION_TYPES.VIEW,
+                canPay: false,
+                canApprove: false,
+                canSubmit: false,
+                canChangeApprover: false,
+                total: 100,
+                chatReportID: undefined,
+            },
+        ];
+        mockCurrentSearchResults = {search: {type: CONST.SEARCH.DATA_TYPES.EXPENSE_REPORT}};
+
+        // When the bulk actions are created for an expense-report search
+        const {result} = renderHook(() => useSearchBulkActions({queryJSON: expenseReportQueryJSON}), {wrapper: OnyxListItemProvider});
+
+        // Then the hook renders its options instead of throwing, and Merge stays hidden until the results load
+        await waitFor(() => {
+            expect(result.current.headerButtonsOptions.length).toBeGreaterThan(0);
+        });
+        expect(result.current.headerButtonsOptions.some((option) => option.value === CONST.SEARCH.BULK_ACTION_TYPES.MERGE_REPORTS)).toBe(false);
+    });
+
     it('handleBasicExport with manual selection does not track any export', async () => {
         mockAreAllMatchingItemsSelected = false;
         mockSelectedTransactions = {tx1: makeSelectedTransaction()};