Add debug logs when discarding atomic txs (#335)

* add logs

* fix tests

* fix typo

* clean up logs

* remove from atomic backends

* cleanup

* final cleanup

* switch

* error -> err

plugin/evm/vm.go

@@ -774,6 +774,7 @@ func (vm *VM) preBatchOnFinalizeAndAssemble(header *types.Header, state *state.S
 		rules := vm.chainConfig.AvalancheRules(header.Number, header.Time)
 		if err := vm.verifyTx(tx, header.ParentHash, header.BaseFee, state, rules); err != nil {
 			// Discard the transaction from the mempool on failed verification.
+			log.Debug("discarding tx from mempool on failed verification", "txID", tx.ID(), "err", err)
 			vm.mempool.DiscardCurrentTx(tx.ID())
 			state.RevertToSnapshot(snapshot)
 			continue
@@ -783,6 +784,7 @@ func (vm *VM) preBatchOnFinalizeAndAssemble(header *types.Header, state *state.S
 		if err != nil {
 			// Discard the transaction from the mempool and error if the transaction
 			// cannot be marshalled. This should never happen.
+			log.Debug("discarding tx due to unmarshal err", "txID", tx.ID(), "err", err)
 			vm.mempool.DiscardCurrentTx(tx.ID())
 			return nil, nil, nil, fmt.Errorf("failed to marshal atomic transaction %s due to %w", tx.ID(), err)
 		}
@@ -854,6 +856,7 @@ func (vm *VM) postBatchOnFinalizeAndAssemble(header *types.Header, state *state.
 			// valid, but we discard it early here based on the assumption that the proposed
 			// block will most likely be accepted.
 			// Discard the transaction from the mempool on failed verification.
+			log.Debug("discarding tx due to overlapping input utxos", "txID", tx.ID())
 			vm.mempool.DiscardCurrentTx(tx.ID())
 			continue
 		}
@@ -864,6 +867,7 @@ func (vm *VM) postBatchOnFinalizeAndAssemble(header *types.Header, state *state.
 			// if it fails verification here.
 			// Note: prior to this point, we have not modified [state] so there is no need to
 			// revert to a snapshot if we discard the transaction prior to this point.
+			log.Debug("discarding tx from mempool due to failed verification", "txID", tx.ID(), "err", err)
 			vm.mempool.DiscardCurrentTx(tx.ID())
 			state.RevertToSnapshot(snapshot)
 			continue
@@ -884,6 +888,7 @@ func (vm *VM) postBatchOnFinalizeAndAssemble(header *types.Header, state *state.
 		if err != nil {
 			// If we fail to marshal the batch of atomic transactions for any reason,
 			// discard the entire set of current transactions.
+			log.Debug("discarding txs due to error marshaling atomic transactions", "err", err)
 			vm.mempool.DiscardCurrentTxs()
 			return nil, nil, nil, fmt.Errorf("failed to marshal batch of atomic transactions due to %w", err)
 		}
@@ -1166,6 +1171,7 @@ func (vm *VM) buildBlock(_ context.Context) (snowman.Block, error) {
 	// Note: the status of block is set by ChainState
 	blk, err := vm.newBlock(block)
 	if err != nil {
+		log.Debug("discarding txs due to error making new block", "err", err)
 		vm.mempool.DiscardCurrentTxs()
 		return nil, err
 	}