wallet: don't include unconfirmed v3 txs with children in available coins

Author: ishaanam

src/wallet/spend.cpp

@@ -390,8 +390,11 @@ CoinsResult AvailableCoins(const CWallet& wallet,
             if (nDepth == 0 && params.check_version_trucness) {
                 if (coinControl->m_version == TRUC_VERSION) {
                     if (wtx.tx->version != TRUC_VERSION) continue;
+                    // this unconfirmed v3 transaction already has a child
+                    if (wtx.truc_child_in_mempool.has_value()) continue;
                 } else {
                     if (wtx.tx->version == TRUC_VERSION) continue;
+                    Assume(!wtx.truc_child_in_mempool.has_value());
                 }
             }
 

src/wallet/transaction.h

@@ -258,6 +258,10 @@ class CWalletTx
     // BlockConflicted.
     std::set<Txid> mempool_conflicts;
 
+    // Track v3 mempool tx that spends from this tx
+    // so that we don't try to create another unconfirmed child
+    std::optional<Txid> truc_child_in_mempool;
+
     template<typename Stream>
     void Serialize(Stream& s) const
     {

src/wallet/wallet.cpp

@@ -30,6 +30,7 @@
 #include <node/types.h>
 #include <outputtype.h>
 #include <policy/feerate.h>
+#include <policy/truc_policy.h>
 #include <primitives/block.h>
 #include <primitives/transaction.h>
 #include <psbt.h>
@@ -1388,6 +1389,22 @@ void CWallet::transactionAddedToMempool(const CTransactionRef& tx) {
                 return wtx.mempool_conflicts.insert(txid).second ? TxUpdate::CHANGED : TxUpdate::UNCHANGED;
             });
         }
+
+    }
+
+    if (tx->version == TRUC_VERSION) {
+        // Unconfirmed TRUC transactions are only allowed a 1-parent-1-child topology.
+        // For any unconfirmed v3 parents (there should be a maximum of 1 except in reorgs),
+        // record this child so the wallet doesn't try to spend any other outputs
+        for (const CTxIn& tx_in : tx->vin) {
+            auto parent_it = mapWallet.find(tx_in.prevout.hash);
+            if (parent_it != mapWallet.end()) {
+                CWalletTx& parent_wtx = parent_it->second;
+                if (parent_wtx.isUnconfirmed()) {
+                    parent_wtx.truc_child_in_mempool = tx->GetHash();
+                }
+            }
+        }
     }
 }
 
@@ -1441,6 +1458,22 @@ void CWallet::transactionRemovedFromMempool(const CTransactionRef& tx, MemPoolRe
             });
         }
     }
+
+    if (tx->version == TRUC_VERSION) {
+        // If this tx has a parent, unset its truc_child_in_mempool to make it possible
+        // to spend from the parent again. If this tx was replaced by another
+        // child of the same parent, transactionAddedToMempool
+        // will update truc_child_in_mempool
+        for (const CTxIn& tx_in : tx->vin) {
+            auto parent_it = mapWallet.find(tx_in.prevout.hash);
+            if (parent_it != mapWallet.end()) {
+                CWalletTx& parent_wtx = parent_it->second;
+                if (parent_wtx.truc_child_in_mempool == tx->GetHash()) {
+                    parent_wtx.truc_child_in_mempool = std::nullopt;
+                }
+            }
+        }
+    }
 }
 
 void CWallet::blockConnected(ChainstateRole role, const interfaces::BlockInfo& block)