Merge pull request #830 from onflow/mpeter/fix-eip-1559-tx-fee-calculations

Fix transaction fee calculations to comply with `EIP-1559`

Author: m-Peter

eth/types/types.go

@@ -536,7 +536,15 @@ func MarshalReceipt(
 		"effectiveGasPrice": (*hexutil.Big)(receipt.EffectiveGasPrice),
 	}
 
-	if _, ok := tx.(models.DirectCall); ok {
+	// Dynamically fallback to `BaseFeePerGas` when computing `EffectiveGasPrice`
+	// to fix historical gasPrice = 0 issues.
+	// This avoids the need to re-index the entire chain for previously stored
+	// transactions. For any transaction that had a `0` gas price, regardless
+	// whether they were COA interactions or regular EVM, we
+	// set the `effectiveGasPrice` to the value of `BaseFeePerGas`,
+	// which is the minimum amount of gas price required by any
+	// transaction, in order to comply with EIP-1559.
+	if receipt.EffectiveGasPrice.Sign() == 0 {
 		fields["effectiveGasPrice"] = (*hexutil.Big)(models.BaseFeePerGas)
 	}
 

models/receipt_test.go

@@ -13,6 +13,8 @@ func Test_DecodeReceipts(t *testing.T) {
 	_, receipt, _, err := decodeTransactionEvent(cdcEv)
 	require.NoError(t, err)
 
+	assert.Equal(t, BaseFeePerGas, receipt.EffectiveGasPrice)
+
 	for i, l := range rec.Logs {
 		assert.ObjectsAreEqualValues(l, receipt.Logs[i])
 		for j, tt := range l.Topics {

models/transaction.go

@@ -160,6 +160,58 @@ type TransactionCall struct {
 	*gethTypes.Transaction
 }
 
+func (tc TransactionCall) GasPrice() *big.Int {
+	// EIP-1559 introduced a new fee model in Ethereum that replaces the
+	// legacy `GasPrice` with `MaxFeePerGas` and `MaxPriorityFeePerGas`.
+	// However, many Ethereum tools and wallets (such as MetaMask, Hardhat, etc.)
+	// still rely on reading `GasPrice`, even if it’s not explicitly set.
+	//
+	// When a user submits an EIP-1559 transaction type, `GasPrice` is not
+	// specified, Ethereum nodes typically return the current `BaseFeePerGas`
+	// as the effective `GasPrice` for compatibility reasons.
+	//
+	// This behavior is mirrored here in Flow EVM Gateway: if `GasPrice` is zero,
+	// we return the configured `BaseFeePerGas` to satisfy the expectations of
+	// these tools.
+	//
+	// This does NOT affect Flow’s actual transaction fee calculation,
+	// this is purely for compatibility.
+	if tc.Transaction.GasPrice().Sign() == 0 {
+		return BaseFeePerGas
+	}
+	return tc.Transaction.GasPrice()
+}
+
+func (tc TransactionCall) GasFeeCap() *big.Int {
+	// `GasFeeCap` represents the `MaxFeePerGas` in EIP-1559, the maximum fee
+	// a user is willing to pay. Ethereum clients expect a non-zero value when
+	// calculating effective gas prices for compatibility.
+	//
+	// If the user does not provide a value (zero), this method returns the
+	// configured `BaseFeePerGas` to avoid confusion and comply with expected
+	// EVM behavior. This ensures Ethereum tooling can still function correctly
+	// when interacting with Flow EVM.
+	if tc.Transaction.GasFeeCap().Sign() == 0 {
+		return BaseFeePerGas
+	}
+	return tc.Transaction.GasFeeCap()
+}
+
+func (tc TransactionCall) GasTipCap() *big.Int {
+	// `GasTipCap` represents the `MaxPriorityFeePerGas` in EIP-1559, the optional
+	// "tip" to incentivize block inclusion. Ethereum expects this value to be
+	// explicitly defined or it defaults to something reasonable like the base fee.
+	//
+	// To satisfy Ethereum clients and maintain expected behavior, when this value
+	// is zero, Flow EVM returns the configured `BaseFeePerGas` as a safe default.
+	// This ensures Ethereum tools can continue to compute `EffectiveGasPrice`
+	// without errors.
+	if tc.Transaction.GasTipCap().Sign() == 0 {
+		return BaseFeePerGas
+	}
+	return tc.Transaction.GasTipCap()
+}
+
 func (tc TransactionCall) Hash() common.Hash {
 	return tc.Transaction.Hash()
 }
@@ -246,7 +298,11 @@ func decodeTransactionEvent(event cadence.Event) (
 				err,
 			)
 		}
-		receipt.EffectiveGasPrice = gethTx.EffectiveGasTipValue(nil)
+		if gethTx.GasPrice().Sign() == 0 {
+			receipt.EffectiveGasPrice = BaseFeePerGas
+		} else {
+			receipt.EffectiveGasPrice = gethTx.EffectiveGasTipValue(nil)
+		}
 		tx = TransactionCall{Transaction: gethTx}
 	}
 

models/transaction_test.go

@@ -123,7 +123,7 @@ func Test_DecodeEVMTransaction(t *testing.T) {
 	assert.Equal(t, big.NewInt(0), decTx.Value())
 	assert.Equal(t, uint8(0), decTx.Type())
 	assert.Equal(t, uint64(125_000), decTx.Gas())
-	assert.Equal(t, big.NewInt(0), decTx.GasPrice())
+	assert.Equal(t, BaseFeePerGas, decTx.GasPrice())
 	assert.Equal(t, uint64(0), decTx.BlobGas())
 	assert.Equal(t, uint64(347), decTx.Size())
 }
@@ -223,7 +223,7 @@ func Test_UnmarshalTransaction(t *testing.T) {
 		assert.Equal(t, big.NewInt(0), decTx.Value())
 		assert.Equal(t, uint8(0), decTx.Type())
 		assert.Equal(t, uint64(125_000), decTx.Gas())
-		assert.Equal(t, big.NewInt(0), decTx.GasPrice())
+		assert.Equal(t, BaseFeePerGas, decTx.GasPrice())
 		assert.Equal(t, uint64(0), decTx.BlobGas())
 		assert.Equal(t, uint64(347), decTx.Size())
 	})

tests/web3js/eth_batch_retrieval_test.js

@@ -19,10 +19,12 @@ it('should retrieve batch transactions', async () => {
         assert.equal(tx.type, 0, "wrong type")
         assert.equal(tx.transactionIndex, i, "wrong index")
         assert.isBelow(i, batchSize, "wrong batch size")
+        assert.equal(tx.gasPrice, 1n)
 
         let receipt = await web3.eth.getTransactionReceipt(tx.hash)
         cumulativeGasUsed += receipt.gasUsed
 
         assert.equal(receipt.cumulativeGasUsed, cumulativeGasUsed)
+        assert.equal(receipt.effectiveGasPrice, 1n)
     }
 })

tests/web3js/eth_non_interactive_test.js

@@ -261,6 +261,7 @@ it('should get transaction', async () => {
     assert.isNotEmpty(tx.r)
     assert.isNotEmpty(tx.s)
     assert.equal(tx.transactionIndex, 2)
+    assert.equal(tx.gasPrice, 1n)
 
     let rcp = await web3.eth.getTransactionReceipt(tx.hash)
     assert.isNotEmpty(rcp)
@@ -272,6 +273,7 @@ it('should get transaction', async () => {
     assert.equal(rcp.cumulativeGasUsed, 744655n)
     assert.equal(rcp.transactionHash, tx.hash)
     assert.equal(rcp.status, conf.successStatus)
+    assert.equal(rcp.effectiveGasPrice, 1n)
 })
 
 it('should return null for non-existing blocks and receipts', async () => {