changes for review from guggero

wallet/wallet.go

@@ -2385,15 +2385,18 @@ type GetTransactionResult struct {
 // transaction is returned in a Block structure which records properties about
 // the block. A bool is also returned to denote if the transaction previously
 // existed in the database or not.
+// The backend must have a transaction index to poll a confirmed transaction
+// that does not exist in the internal wallet.
 func (w *Wallet) GetTransaction(txHash *chainhash.Hash) (*GetTransactionResult,
 	bool, error) {
 
-	var res GetTransactionResult
-	chainClient := w.chainClient
-	if chainClient == nil {
-		return nil, false, errors.New("no chain server client")
+	chainClient, err := w.requireChainClient()
+	if err != nil {
+		return nil, false, err
 	}
 
+	var res GetTransactionResult
+
 	// In case the transaction is unconfirmed it could due to race condition
 	// confirm during the time we receive it from the backend and check it
 	// in the database.
@@ -2406,17 +2409,26 @@ func (w *Wallet) GetTransaction(txHash *chainhash.Hash) (*GetTransactionResult,
 
 	// Get the transaction information from directly calling the backend
 	// endpoint.
+	var backendErr error
 	var txResult *btcjson.TxRawResult
 	switch client := chainClient.(type) {
 	case *chain.RPCClient:
 		txResult, err = client.GetRawTransactionVerbose(txHash)
 		if err != nil {
-			return nil, false, err
+			// If the backend returned an error we will still try to
+			// find the transaction in the database, but return the
+			// error if it was also not found there.
+			backendErr = err
+			bestHeight = 0
 		}
 	case *chain.BitcoindClient:
 		txResult, err = client.GetRawTransactionVerbose(txHash)
 		if err != nil {
-			return nil, false, err
+			// If the backend returned an error we will still try to
+			// find the transaction in the database, but return the
+			// error if it was also not found there.
+			backendErr = err
+			bestHeight = 0
 		}
 	case *chain.NeutrinoClient:
 		return nil, false, errors.New("not supported with neutrino client")
@@ -2430,20 +2442,8 @@ func (w *Wallet) GetTransaction(txHash *chainhash.Hash) (*GetTransactionResult,
 	// db can be queried directly without this.
 	var blockHash *chainhash.Hash
 	var height int32 = -1
-	if txResult.BlockHash != "" {
-		blockHashBytes, err := hex.DecodeString(txResult.BlockHash)
-		if err != nil {
-			return nil, false, err
-		}
-
-		// The byte is reversed due to different endianness in response
-		// and call.
-		reversed := make([]byte, len(blockHashBytes))
-		for i, n := range blockHashBytes {
-			j := len(blockHashBytes) - i - 1
-			reversed[j] = n
-		}
-		blockHash, err = chainhash.NewHash(reversed)
+	if txResult != nil && txResult.BlockHash != "" {
+		blockHash, err = chainhash.NewHashFromStr(txResult.BlockHash)
 		if err != nil {
 			return nil, false, err
 		}
@@ -2461,11 +2461,6 @@ func (w *Wallet) GetTransaction(txHash *chainhash.Hash) (*GetTransactionResult,
 			if err != nil {
 				return nil, false, err
 			}
-		case *chain.NeutrinoClient:
-			height, err = client.GetBlockHeight(blockHash)
-			if err != nil {
-				return nil, false, err
-			}
 		}
 
 		// We know that the transaction definitively is in a specific
@@ -2502,8 +2497,9 @@ func (w *Wallet) GetTransaction(txHash *chainhash.Hash) (*GetTransactionResult,
 			return false, nil
 		}
 
-		return w.TxStore.RangeTransactions(txmgrNs, bestHeight,
-			height, rangeFn)
+		return w.TxStore.RangeTransactions(
+			txmgrNs, bestHeight, height, rangeFn,
+		)
 	})
 	if err != nil {
 		return nil, false, err
@@ -2512,6 +2508,12 @@ func (w *Wallet) GetTransaction(txHash *chainhash.Hash) (*GetTransactionResult,
 	// We need to build the transaction to return as the response if it was
 	// not found in the database.
 	if summary == nil {
+		// Return the backend error if the transaction was not found in
+		// the database.
+		if backendErr != nil {
+			return nil, false, backendErr
+		}
+
 		txRaw, err := hex.DecodeString(txResult.Hex)
 		if err != nil {
 			return nil, false, err