Merge #19517: psbt: Increment input value sum only once per UTXO in decodepsbt

7512278 Increment input value sum only once per UTXO in decodepsbt (Andrew Chow)

Pull request description:

  Refactors the UTXO processing of `decodepsbt` to extract the relevant `CTxOut` and handle the input amounts from that. This avoids double counting the input value.

  Fixes #19516

ACKs for top commit:
  sipa:
    utACK 7512278
  ryanofsky:
    Code review ACK 7512278

Tree-SHA512: 004ec1597790a88a98098f1a26534d10ab0130a438dec0913522a529a8d7f18ad679948617dbcad6e541fbab5bcb2682aeed386b67746807c03b64d76ce5441d

Author: fanquake

src/rpc/rawtransaction.cpp

@@ -1105,39 +1105,38 @@ UniValue decodepsbt(const JSONRPCRequest& request)
         UniValue in(UniValue::VOBJ);
         // UTXOs
         bool have_a_utxo = false;
+        CTxOut txout;
         if (!input.witness_utxo.IsNull()) {
-            const CTxOut& txout = input.witness_utxo;
-
-            UniValue out(UniValue::VOBJ);
-
-            out.pushKV("amount", ValueFromAmount(txout.nValue));
-            if (MoneyRange(txout.nValue) && MoneyRange(total_in + txout.nValue)) {
-                total_in += txout.nValue;
-            } else {
-                // Hack to just not show fee later
-                have_all_utxos = false;
-            }
+            txout = input.witness_utxo;
 
             UniValue o(UniValue::VOBJ);
             ScriptToUniv(txout.scriptPubKey, o, true);
+
+            UniValue out(UniValue::VOBJ);
+            out.pushKV("amount", ValueFromAmount(txout.nValue));
             out.pushKV("scriptPubKey", o);
+
             in.pushKV("witness_utxo", out);
+
             have_a_utxo = true;
         }
         if (input.non_witness_utxo) {
+            txout = input.non_witness_utxo->vout[psbtx.tx->vin[i].prevout.n];
+
             UniValue non_wit(UniValue::VOBJ);
             TxToUniv(*input.non_witness_utxo, uint256(), non_wit, false);
             in.pushKV("non_witness_utxo", non_wit);
-            CAmount utxo_val = input.non_witness_utxo->vout[psbtx.tx->vin[i].prevout.n].nValue;
-            if (MoneyRange(utxo_val) && MoneyRange(total_in + utxo_val)) {
-                total_in += utxo_val;
+
+            have_a_utxo = true;
+        }
+        if (have_a_utxo) {
+            if (MoneyRange(txout.nValue) && MoneyRange(total_in + txout.nValue)) {
+                total_in += txout.nValue;
             } else {
                 // Hack to just not show fee later
                 have_all_utxos = false;
             }
-            have_a_utxo = true;
-        }
-        if (!have_a_utxo) {
+        } else {
             have_all_utxos = false;
         }