chore: adjust review comments

* do not cast gasUsed
* adjust comment on GasPrice method
* add nil check for args.Data
* log gas price changes in the sync service

core/rollup_fee.go

@@ -16,7 +16,7 @@ func CalculateRollupFee(data []byte, gasUsed uint64, dataPrice, executionPrice *
 	dataLen := int64(ROLLUP_BASE_TX_SIZE + len(data))
 	// get the data fee
 	dataFee := new(big.Int).Mul(dataPrice, big.NewInt(dataLen))
-	executionFee := new(big.Int).Mul(executionPrice, big.NewInt(int64(gasUsed)))
+	executionFee := new(big.Int).Mul(executionPrice, new(big.Int).SetUint64(gasUsed))
 	fee := new(big.Int).Add(dataFee, executionFee)
 	return fee
 }

internal/ethapi/api.go

@@ -63,7 +63,7 @@ func NewPublicEthereumAPI(b Backend) *PublicEthereumAPI {
 	return &PublicEthereumAPI{b}
 }
 
-// GasPrice returns 1 gwei always. Rationale: https://github.com/ethereum-optimism/roadmap/issues/715
+// GasPrice always returns 1 gwei. See `DoEstimateGas` below for context.
 func (s *PublicEthereumAPI) GasPrice(ctx context.Context) (*hexutil.Big, error) {
 	return (*hexutil.Big)(big.NewInt(defaultGasPrice)), nil
 }
@@ -1001,6 +1001,10 @@ func (s *PublicBlockChainAPI) Call(ctx context.Context, args CallArgs, blockNrOr
 // fees can compensate for the additional costs the sequencer pays for publishing the
 // transaction calldata
 func DoEstimateGas(ctx context.Context, b Backend, args CallArgs, blockNrOrHash rpc.BlockNumberOrHash, gasCap *big.Int) (hexutil.Uint64, error) {
+	if args.Data == nil {
+		return 0, errors.New("transaction data cannot be nil")
+	}
+
 	// 1. get the gas that would be used by the transaction
 	gasUsed, err := legacyDoEstimateGas(ctx, b, args, blockNrOrHash, gasCap)
 	if err != nil {

rollup/sync_service.go

@@ -366,6 +366,7 @@ func (s *SyncService) sequence() error {
 		return err
 	}
 	s.L1gpo.SetL1GasPrice(l1GasPrice)
+	log.Info("Adjusted L1 Gas Price", "gasprice", l1GasPrice)
 
 	// Only the sequencer needs to poll for enqueue transactions
 	// and then can choose when to apply them. We choose to apply