Refactor transaction builder (Layr-Labs#92)

common/ethclient.go

@@ -39,5 +39,6 @@ type EthClient interface {
 	TransactionInBlock(ctx context.Context, blockHash common.Hash, index uint) (*types.Transaction, error)
 	TransactionReceipt(ctx context.Context, txHash common.Hash) (*types.Receipt, error)
 	EstimateGasPriceAndLimitAndSendTx(ctx context.Context, tx *types.Transaction, tag string, value *big.Int) (*types.Receipt, error)
+	UpdateGas(ctx context.Context, tx *types.Transaction, value *big.Int) (*types.Transaction, error)
 	EnsureTransactionEvaled(ctx context.Context, tx *types.Transaction, tag string) (*types.Receipt, error)
 }

common/geth/client.go

@@ -98,19 +98,18 @@ func (c *EthClient) GetNoSendTransactOpts() *bind.TransactOpts {
 	return c.NoSendTransactOpts
 }
 
-// EstimateGasPriceAndLimitAndSendTx sends and returns an otherwise identical txn
-// to the one provided but with updated gas prices sampled from the existing network
-// conditions and an accurate gasLimit
+// UpdateGas returns an otherwise identical txn to the one provided but with updated
+// gas prices sampled from the existing network conditions and an accurate gasLimit.
+// Note that this method does not publish the transaction.
 //
 // Note: tx must be a to a contract, not an EOA
 //
 // Slightly modified from: https://github.com/ethereum-optimism/optimism/blob/ec266098641820c50c39c31048aa4e953bece464/batch-submitter/drivers/sequencer/driver.go#L314
-func (c *EthClient) EstimateGasPriceAndLimitAndSendTx(
+func (c *EthClient) UpdateGas(
 	ctx context.Context,
 	tx *types.Transaction,
-	tag string,
 	value *big.Int,
-) (*types.Receipt, error) {
+) (*types.Transaction, error) {
 	gasTipCap, err := c.SuggestGasTipCap(ctx)
 	if err != nil {
 		// If the transaction failed because the backend does not support
@@ -135,7 +134,7 @@ func (c *EthClient) EstimateGasPriceAndLimitAndSendTx(
 	if err != nil {
 		return nil, err
 	}
-	gasFeeCap := new(big.Int).Add(header.BaseFee, gasTipCap)
+	gasFeeCap := getGasFeeCap(gasTipCap, header.BaseFee)
 
 	// The estimated gas limits performed by RawTransact fail semi-regularly
 	// with out of gas exceptions. To remedy this we extract the internal calls
@@ -154,10 +153,8 @@ func (c *EthClient) EstimateGasPriceAndLimitAndSendTx(
 		return nil, err
 	}
 
-	opts, err := bind.NewKeyedTransactorWithChainID(c.privateKey, tx.ChainId())
-	if err != nil {
-		return nil, fmt.Errorf("EstimateGasPriceAndLimitAndSendTx: cannot create transactOpts: %w", err)
-	}
+	opts := new(bind.TransactOpts)
+	*opts = *c.NoSendTransactOpts
 	opts.Context = ctx
 	opts.Nonce = new(big.Int).SetUint64(tx.Nonce())
 	opts.GasTipCap = gasTipCap
@@ -174,7 +171,25 @@ func (c *EthClient) EstimateGasPriceAndLimitAndSendTx(
 		c.Contracts[*tx.To()] = contract
 	}
 
-	tx, err = contract.RawTransact(opts, tx.Data())
+	return contract.RawTransact(opts, tx.Data())
+}
+
+// EstimateGasPriceAndLimitAndSendTx sends and returns an otherwise identical txn
+// to the one provided but with updated gas prices sampled from the existing network
+// conditions and an accurate gasLimit
+//
+// Note: tx must be a to a contract, not an EOA
+func (c *EthClient) EstimateGasPriceAndLimitAndSendTx(
+	ctx context.Context,
+	tx *types.Transaction,
+	tag string,
+	value *big.Int,
+) (*types.Receipt, error) {
+	tx, err := c.UpdateGas(ctx, tx, value)
+	if err != nil {
+		return nil, fmt.Errorf("EstimateGasPriceAndLimitAndSendTx: failed to update gas for txn (%s): %w", tag, err)
+	}
+	err = c.SendTransaction(ctx, tx)
 	if err != nil {
 		return nil, fmt.Errorf("EstimateGasPriceAndLimitAndSendTx: failed to send txn (%s): %w", tag, err)
 	}
@@ -204,6 +219,13 @@ func (c *EthClient) EnsureTransactionEvaled(ctx context.Context, tx *types.Trans
 	return receipt, nil
 }
 
+// getGasFeeCap returns the gas fee cap for a transaction, calculated as:
+// gasFeeCap = 2 * baseFee + gasTipCap
+// Rationale: https://www.blocknative.com/blog/eip-1559-fees
+func getGasFeeCap(gasTipCap *big.Int, baseFee *big.Int) *big.Int {
+	return new(big.Int).Add(new(big.Int).Mul(baseFee, big.NewInt(2)), gasTipCap)
+}
+
 func addGasBuffer(gasLimit uint64) uint64 {
 	return 6 * gasLimit / 5 // add 20% buffer to gas limit
 }

common/mock/ethclient.go

@@ -185,6 +185,12 @@ func (mock *MockEthClient) TransactionReceipt(ctx context.Context, txHash common
 	return result, args.Error(1)
 }
 
+func (mock *MockEthClient) UpdateGas(ctx context.Context, tx *types.Transaction, value *big.Int) (*types.Transaction, error) {
+	args := mock.Called()
+	result := args.Get(0)
+	return result.(*types.Transaction), args.Error(1)
+}
+
 func (mock *MockEthClient) EstimateGasPriceAndLimitAndSendTx(ctx context.Context, tx *types.Transaction, tag string, value *big.Int) (*types.Receipt, error) {
 	args := mock.Called()
 	var result *types.Receipt