wallet: skip BnB when SFFO is active

Co-authored-by: furszy <matiasfurszyfer@protonmail.com>

Author: murchandamus

src/wallet/spend.cpp

@@ -693,9 +693,12 @@ util::Result<SelectionResult> ChooseSelectionResult(interfaces::Chain& chain, co
     // Maximum allowed weight
     int max_inputs_weight = MAX_STANDARD_TX_WEIGHT - (coin_selection_params.tx_noinputs_size * WITNESS_SCALE_FACTOR);
 
-    if (auto bnb_result{SelectCoinsBnB(groups.positive_group, nTargetValue, coin_selection_params.m_cost_of_change, max_inputs_weight)}) {
-        results.push_back(*bnb_result);
-    } else append_error(bnb_result);
+    // SFFO frequently causes issues in the context of changeless input sets: skip BnB when SFFO is active
+    if (!coin_selection_params.m_subtract_fee_outputs) {
+        if (auto bnb_result{SelectCoinsBnB(groups.positive_group, nTargetValue, coin_selection_params.m_cost_of_change, max_inputs_weight)}) {
+            results.push_back(*bnb_result);
+        } else append_error(bnb_result);
+    }
 
     // As Knapsack and SRD can create change, also deduce change weight.
     max_inputs_weight -= (coin_selection_params.change_output_size * WITNESS_SCALE_FACTOR);

src/wallet/test/coinselector_tests.cpp

@@ -320,7 +320,6 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
     coin_selection_params_bnb.m_change_fee = coin_selection_params_bnb.m_effective_feerate.GetFee(coin_selection_params_bnb.change_output_size);
     coin_selection_params_bnb.m_cost_of_change = coin_selection_params_bnb.m_effective_feerate.GetFee(coin_selection_params_bnb.change_spend_size) + coin_selection_params_bnb.m_change_fee;
     coin_selection_params_bnb.min_viable_change = coin_selection_params_bnb.m_effective_feerate.GetFee(coin_selection_params_bnb.change_spend_size);
-    coin_selection_params_bnb.m_subtract_fee_outputs = true;
 
     {
         std::unique_ptr<CWallet> wallet = NewWallet(m_node);
@@ -345,6 +344,7 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
 
         CoinsResult available_coins;
 
+        coin_selection_params_bnb.m_effective_feerate = CFeeRate(0);
         add_coin(available_coins, *wallet, 5 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
         add_coin(available_coins, *wallet, 3 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
         add_coin(available_coins, *wallet, 2 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
@@ -355,7 +355,7 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
         PreSelectedInputs selected_input;
         selected_input.Insert(select_coin, coin_selection_params_bnb.m_subtract_fee_outputs);
         available_coins.Erase({available_coins.coins[OutputType::BECH32].begin()->outpoint});
-        coin_selection_params_bnb.m_effective_feerate = CFeeRate(0);
+
         LOCK(wallet->cs_wallet);
         const auto result10 = SelectCoins(*wallet, available_coins, selected_input, 10 * CENT, coin_control, coin_selection_params_bnb);
         BOOST_CHECK(result10);
@@ -370,12 +370,14 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
         coin_selection_params_bnb.m_effective_feerate = CFeeRate(5000);
         coin_selection_params_bnb.m_long_term_feerate = CFeeRate(3000);
 
-        add_coin(available_coins, *wallet, 10 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
-        add_coin(available_coins, *wallet, 9 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
-        add_coin(available_coins, *wallet, 1 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        // Add selectable outputs, increasing their raw amounts by their input fee to make the effective value equal to the raw amount
+        CAmount input_fee = coin_selection_params_bnb.m_effective_feerate.GetFee(/*num_bytes=*/68); // bech32 input size (default test output type)
+        add_coin(available_coins, *wallet, 10 * CENT + input_fee, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 9 * CENT + input_fee, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 1 * CENT + input_fee, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
 
         expected_result.Clear();
-        add_coin(10 * CENT, 2, expected_result);
+        add_coin(10 * CENT + input_fee, 2, expected_result);
         CCoinControl coin_control;
         const auto result11 = SelectCoins(*wallet, available_coins, /*pre_set_inputs=*/{}, 10 * CENT, coin_control, coin_selection_params_bnb);
         BOOST_CHECK(EquivalentResult(expected_result, *result11));
@@ -385,13 +387,15 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
         coin_selection_params_bnb.m_effective_feerate = CFeeRate(3000);
         coin_selection_params_bnb.m_long_term_feerate = CFeeRate(5000);
 
-        add_coin(available_coins, *wallet, 10 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
-        add_coin(available_coins, *wallet, 9 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
-        add_coin(available_coins, *wallet, 1 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        // Add selectable outputs, increasing their raw amounts by their input fee to make the effective value equal to the raw amount
+        input_fee = coin_selection_params_bnb.m_effective_feerate.GetFee(/*num_bytes=*/68); // bech32 input size (default test output type)
+        add_coin(available_coins, *wallet, 10 * CENT + input_fee, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 9 * CENT + input_fee, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 1 * CENT + input_fee, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
 
         expected_result.Clear();
-        add_coin(9 * CENT, 2, expected_result);
-        add_coin(1 * CENT, 2, expected_result);
+        add_coin(9 * CENT + input_fee, 2, expected_result);
+        add_coin(1 * CENT + input_fee, 2, expected_result);
         const auto result12 = SelectCoins(*wallet, available_coins, /*pre_set_inputs=*/{}, 10 * CENT, coin_control, coin_selection_params_bnb);
         BOOST_CHECK(EquivalentResult(expected_result, *result12));
         available_coins.Clear();
@@ -400,13 +404,15 @@ BOOST_AUTO_TEST_CASE(bnb_search_test)
         coin_selection_params_bnb.m_effective_feerate = CFeeRate(5000);
         coin_selection_params_bnb.m_long_term_feerate = CFeeRate(3000);
 
-        add_coin(available_coins, *wallet, 10 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
-        add_coin(available_coins, *wallet, 9 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
-        add_coin(available_coins, *wallet, 1 * CENT, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        // Add selectable outputs, increasing their raw amounts by their input fee to make the effective value equal to the raw amount
+        input_fee = coin_selection_params_bnb.m_effective_feerate.GetFee(/*num_bytes=*/68); // bech32 input size (default test output type)
+        add_coin(available_coins, *wallet, 10 * CENT + input_fee, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 9 * CENT + input_fee, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
+        add_coin(available_coins, *wallet, 1 * CENT + input_fee, coin_selection_params_bnb.m_effective_feerate, 6 * 24, false, 0, true);
 
         expected_result.Clear();
-        add_coin(9 * CENT, 2, expected_result);
-        add_coin(1 * CENT, 2, expected_result);
+        add_coin(9 * CENT + input_fee, 2, expected_result);
+        add_coin(1 * CENT + input_fee, 2, expected_result);
         coin_control.m_allow_other_inputs = true;
         COutput select_coin = available_coins.All().at(1); // pre select 9 coin
         coin_control.Select(select_coin.outpoint);