Fix multiple bugs in CreateSparkMintTransactions

Bug fixes in sparkwallet.cpp:
1. Fix typo: mapMultiArgs.at("change") -> mapMultiArgs.at("-change")
   This would cause std::out_of_range exception when -change arg is used.

2. Add empty check before utxos.second.front() access to prevent
   undefined behavior if any entry has an empty vector.

3. Add break after finding matching UTXO entry to avoid unnecessary
   iterations and potential issues.

4. Fix missing strFailReason when SelectCoins fails for reasons other
   than insufficient funds - now sets "Unable to select coins for minting".

5. Fix missing strFailReason when function fails because valueToMint > 0
   at end - now sets descriptive error message.

6. Fix misleading error message: "Signing transaction failed" changed to
   "Transaction not allowed in mempool" for mempool rejection.

Bug fix in wallet.cpp:
- Same typo fix for mapMultiArgs.at("change") in CreateLelantusMintTransactions

These bugs could potentially cause crashes (especially #1 and #2) or
make debugging difficult due to missing/wrong error messages.

Co-authored-by: reuben <[email protected]>

Author: cursoragent

src/spark/sparkwallet.cpp

@@ -959,9 +959,10 @@ bool CSparkWallet::CreateSparkMintTransactions(
                     // Choose coins to use
                     CAmount nValueIn = 0;
                     if (!pwalletMain->SelectCoins(itr->second, nValueToSelect, setCoins, nValueIn, coinControl)) {
-
                         if (nValueIn < nValueToSelect) {
                             strFailReason = _("Insufficient funds");
+                        } else {
+                            strFailReason = _("Unable to select coins for minting");
                         }
                         return false;
                     }
@@ -995,7 +996,7 @@ bool CSparkWallet::CreateSparkMintTransactions(
                             // send change to one of the specified change addresses
                         else if (IsArgSet("-change") && mapMultiArgs.at("-change").size() > 0) {
                             CBitcoinAddress address(
-                                    mapMultiArgs.at("change")[GetRandInt(mapMultiArgs.at("-change").size())]);
+                                    mapMultiArgs.at("-change")[GetRandInt(mapMultiArgs.at("-change").size())]);
                             CKeyID keyID;
                             if (!address.GetKeyID(keyID)) {
                                 strFailReason = _("Bad change address");
@@ -1209,7 +1210,7 @@ bool CSparkWallet::CreateSparkMintTransactions(
                 {
                     CValidationState state;
                     if (!mempool.IsTransactionAllowed(*wtx.tx, state)) {
-                        strFailReason = _("Signing transaction failed");
+                        strFailReason = _("Transaction not allowed in mempool");
                         return false;
                     }
                 }
@@ -1228,12 +1229,14 @@ bool CSparkWallet::CreateSparkMintTransactions(
 
                     bool added = false;
                     for (auto &utxos : valueAndUTXO) {
+                        if (utxos.second.empty())
+                            continue;
                         auto const &o = utxos.second.front();
                         if (o.tx->tx->vout[o.i].scriptPubKey == wtx.tx->vout[nChangePosInOut].scriptPubKey) {
                             utxos.first += val;
                             utxos.second.push_back(out);
-
                             added = true;
+                            break;
                         }
                     }
 
@@ -1253,6 +1256,7 @@ bool CSparkWallet::CreateSparkMintTransactions(
     }
 
     if (!autoMintAll && valueToMint > 0) {
+        strFailReason = _("Unable to mint full amount; only partial minting was possible");
         return false;
     }
 

src/wallet/wallet.cpp

@@ -4487,7 +4487,7 @@ bool CWallet::CreateLelantusMintTransactions(
                             // send change to one of the specified change addresses
                         else if (IsArgSet("-change") && mapMultiArgs.at("-change").size() > 0) {
                             CBitcoinAddress address(
-                                    mapMultiArgs.at("change")[GetRandInt(mapMultiArgs.at("-change").size())]);
+                                    mapMultiArgs.at("-change")[GetRandInt(mapMultiArgs.at("-change").size())]);
                             CKeyID keyID;
                             if (!address.GetKeyID(keyID)) {
                                 strFailReason = _("Bad change address");