Fix: min abs fee

Author: evanlinjin

src/bdk_core/coin_select/coin_selector.rs

@@ -415,7 +415,7 @@ impl<'a> CoinSelector<'a> {
         }
 
         // with drain
-        if fee_with_drain > self.opts.min_absolute_fee
+        if fee_with_drain >= self.opts.min_absolute_fee
             && inputs_minus_outputs >= fee_with_drain + self.opts.min_drain_value
         {
             excess_strategies.insert(

src/wallet/mod.rs

@@ -797,6 +797,14 @@ where
             }
         };
 
+        if params.recipients.is_empty() {
+            let is_drain_all = params.drain_wallet && params.drain_to.is_some();
+            let is_rbf = !params.utxos.is_empty() && params.drain_to.is_some();
+            if !(is_drain_all || is_rbf) {
+                return Err(Error::NoRecipients);
+            }
+        }
+
         let mut tx = Transaction {
             version,
             lock_time,
@@ -831,19 +839,6 @@ where
             outgoing += value;
         }
 
-        fee_amount += fee_rate.fee_wu(tx.weight());
-
-        // Segwit transactions' header is 2WU larger than legacy txs' header,
-        // as they contain a witness marker (1WU) and a witness flag (1WU) (see BIP144).
-        // At this point we really don't know if the resulting transaction will be segwit
-        // or legacy, so we just add this 2WU to the fee_amount - overshooting the fee amount
-        // is better than undershooting it.
-        // If we pass a fee_amount that is slightly higher than the final fee_amount, we
-        // end up with a transaction with a slightly higher fee rate than the requested one.
-        // If, instead, we undershoot, we may end up with a feerate lower than the requested one
-        // - we might come up with non broadcastable txs!
-        fee_amount += fee_rate.fee_wu(2);
-
         if params.change_policy != tx_builder::ChangeSpendPolicy::ChangeAllowed
             && self.change_descriptor.is_none()
         {
@@ -894,7 +889,7 @@ where
             } else {
                 Some(outgoing)
             },
-            target_feerate: fee_rate.as_sat_per_vb() * 4.0, // sats/vb -> sats/wu
+            target_feerate: fee_rate.as_sat_per_vb() / 4.0, // sats/vb -> sats/wu (prefer overshoot)
             min_absolute_fee: fee_amount,
             ..bdk_core::CoinSelectorOpt::fund_outputs(
                 &tx.output,
@@ -1048,7 +1043,7 @@ where
             confirmation_time: None,
             received,
             sent,
-            fee: Some(fee_amount),
+            fee: Some(excess_strategy.fee),
         };
 
         Ok((psbt, transaction_details))