chore(TransactionFeedV2): Show stand by transactions when paginated d…

…ata is empty (#6152)

### Description
6th PR for RET-1207. Adds handling of the empty transaction feed. There
is a possibility that a new user can have a few pending/failed
transactions that are stored in `standByTransactions` but paginated data
returning empty array for the first page. In this case we need to show
stand by transactions.

### Test plan
Adds test to show stand by transactions if the paginated data is empty.

### Related issues

- Relates to RET-1207

### Backwards compatibility
Yes

### Network scalability

If a new NetworkId and/or Network are added in the future, the changes
in this PR will:

- [x] Continue to work without code changes, OR trigger a compilation
error (guaranteeing we find it when a new network is added)

src/transactions/feed/TransactionFeedV2.test.tsx

@@ -312,4 +312,20 @@ describe('TransactionFeedV2', () => {
      */
     await waitFor(() => expect(store.getState().transactions.standbyTransactions.length).toBe(0))
   })
+
+  it('should show stand by transactions if paginated data is empty', async () => {
+    mockFetch.mockResponse(typedResponse({ transactions: [] }))
+    const { store, ...tree } = renderScreen({
+      transactions: {
+        standbyTransactions: [
+          mockTransaction({ transactionHash: '0x01', status: TransactionStatus.Complete }),
+          mockTransaction({ transactionHash: '0x02', status: TransactionStatus.Pending }),
+        ],
+      },
+    })
+
+    await waitFor(() => expect(tree.getByTestId('TransactionList').props.data.length).toBe(2))
+    expect(tree.getByTestId('TransactionList').props.data[0].data.length).toBe(1)
+    expect(tree.getByTestId('TransactionList').props.data[1].data.length).toBe(1)
+  })
 })

src/transactions/feed/TransactionFeedV2.tsx

@@ -115,15 +115,29 @@ function mergeStandByTransactionsInRange({
   standByTransactions: TokenTransaction[]
   currentCursor?: number
 }): TokenTransaction[] {
-  if (transactions.length === 0) return []
+  /**
+   * If the data from the first page is empty - there's no successful transactions in the wallet.
+   * Maybe the user executed a single transaction, it failed and now it's in the standByTransactions.
+   * In this case we need to show whatever we've got in standByTransactions, until we have some
+   * paginated data to merge it with.
+   */
+  const isFirstPage = currentCursor === FIRST_PAGE_TIMESTAMP
+  if (isFirstPage && transactions.length === 0) {
+    return standByTransactions
+  }
+
+  // return empty array for any page other than the first
+  if (transactions.length === 0) {
+    return []
+  }
 
   const allowedNetworks = getAllowedNetworksForTransfers()
   const max = transactions[0].timestamp
   const min = transactions.at(-1)!.timestamp
 
   const standByInRange = standByTransactions.filter((tx) => {
     const inRange = tx.timestamp >= min && tx.timestamp <= max
-    const newTransaction = currentCursor === FIRST_PAGE_TIMESTAMP && tx.timestamp > max
+    const newTransaction = isFirstPage && tx.timestamp > max
     return inRange || newTransaction
   })
   const deduplicatedTransactions = deduplicateTransactions([...transactions, ...standByInRange])