Allow BnB when subtract fee from outputs

Author: achow101

src/wallet/test/coinselector_tests.cpp

@@ -260,6 +260,15 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
     vCoins.at(0).nInputBytes = 40; // Make sure that it has a negative effective value. The next check should assert if this somehow got through. Otherwise it will fail
     BOOST_CHECK(!testWallet.SelectCoinsMinConf( 1 * CENT, filter_standard, GroupCoins(vCoins), setCoinsRet, nValueRet, coin_selection_params_bnb, bnb_used));
 
+    // Test fees subtracted from output:
+    empty_wallet();
+    add_coin(1 * CENT);
+    vCoins.at(0).nInputBytes = 40;
+    BOOST_CHECK(!testWallet.SelectCoinsMinConf( 1 * CENT, filter_standard, GroupCoins(vCoins), setCoinsRet, nValueRet, coin_selection_params_bnb, bnb_used));
+    coin_selection_params_bnb.m_subtract_fee_outputs = true;
+    BOOST_CHECK(testWallet.SelectCoinsMinConf( 1 * CENT, filter_standard, GroupCoins(vCoins), setCoinsRet, nValueRet, coin_selection_params_bnb, bnb_used));
+    BOOST_CHECK_EQUAL(nValueRet, 1 * CENT);
+
     // Make sure that can use BnB when there are preset inputs
     empty_wallet();
     {

src/wallet/wallet.cpp

@@ -2648,7 +2648,11 @@ bool CWallet::SelectCoinsMinConf(const CAmount& nTargetValue, const CoinEligibil
                 if (effective_value > 0) {
                     group.fee += coin.m_input_bytes < 0 ? 0 : coin_selection_params.effective_fee.GetFee(coin.m_input_bytes);
                     group.long_term_fee += coin.m_input_bytes < 0 ? 0 : long_term_feerate.GetFee(coin.m_input_bytes);
-                    group.effective_value += effective_value;
+                    if (coin_selection_params.m_subtract_fee_outputs) {
+                        group.effective_value += coin.txout.nValue;
+                    } else {
+                        group.effective_value += effective_value;
+                    }
                     ++it;
                 } else {
                     it = group.Discard(coin);
@@ -3022,7 +3026,8 @@ bool CWallet::CreateTransaction(interfaces::Chain::Lock& locked_chain, const std
 
             // BnB selector is the only selector used when this is true.
             // That should only happen on the first pass through the loop.
-            coin_selection_params.use_bnb = nSubtractFeeFromAmount == 0; // If we are doing subtract fee from recipient, then don't use BnB
+            coin_selection_params.use_bnb = true;
+            coin_selection_params.m_subtract_fee_outputs = nSubtractFeeFromAmount != 0; // If we are doing subtract fee from recipient, don't use effective values
             // Start with no fee and loop until there is enough fee
             while (true)
             {
@@ -3036,7 +3041,9 @@ bool CWallet::CreateTransaction(interfaces::Chain::Lock& locked_chain, const std
                     nValueToSelect += nFeeRet;
 
                 // vouts to the payees
-                coin_selection_params.tx_noinputs_size = 11; // Static vsize overhead + outputs vsize. 4 nVersion, 4 nLocktime, 1 input count, 1 output count, 1 witness overhead (dummy, flag, stack size)
+                if (!coin_selection_params.m_subtract_fee_outputs) {
+                    coin_selection_params.tx_noinputs_size = 11; // Static vsize overhead + outputs vsize. 4 nVersion, 4 nLocktime, 1 input count, 1 output count, 1 witness overhead (dummy, flag, stack size)
+                }
                 for (const auto& recipient : vecSend)
                 {
                     CTxOut txout(recipient.nAmount, recipient.scriptPubKey);
@@ -3053,7 +3060,9 @@ bool CWallet::CreateTransaction(interfaces::Chain::Lock& locked_chain, const std
                         }
                     }
                     // Include the fee cost for outputs. Note this is only used for BnB right now
-                    coin_selection_params.tx_noinputs_size += ::GetSerializeSize(txout, PROTOCOL_VERSION);
+                    if (!coin_selection_params.m_subtract_fee_outputs) {
+                        coin_selection_params.tx_noinputs_size += ::GetSerializeSize(txout, PROTOCOL_VERSION);
+                    }
 
                     if (IsDust(txout, chain().relayDustFee()))
                     {

src/wallet/wallet.h

@@ -715,6 +715,8 @@ struct CoinSelectionParams
     size_t change_spend_size = 0;
     CFeeRate effective_fee = CFeeRate(0);
     size_t tx_noinputs_size = 0;
+    //! Indicate that we are subtracting the fee from outputs
+    bool m_subtract_fee_outputs = false;
 
     CoinSelectionParams(bool use_bnb, size_t change_output_size, size_t change_spend_size, CFeeRate effective_fee, size_t tx_noinputs_size) : use_bnb(use_bnb), change_output_size(change_output_size), change_spend_size(change_spend_size), effective_fee(effective_fee), tx_noinputs_size(tx_noinputs_size) {}
     CoinSelectionParams() {}