Apply fee abstraction on v0.5.1

tests/integration/x/vm/test_gas.go

@@ -0,0 +1,216 @@
+package vm
+
+import (
+	"math/big"
+
+	"github.com/cosmos/evm/testutil/integration/evm/factory"
+	"github.com/cosmos/evm/testutil/integration/evm/grpc"
+	"github.com/cosmos/evm/testutil/integration/evm/network"
+	testkeyring "github.com/cosmos/evm/testutil/keyring"
+	"github.com/cosmos/evm/x/vm/keeper"
+	"github.com/cosmos/evm/x/vm/types"
+
+	sdkmath "cosmossdk.io/math"
+
+	sdk "github.com/cosmos/cosmos-sdk/types"
+	authtypes "github.com/cosmos/cosmos-sdk/x/auth/types"
+	banktypes "github.com/cosmos/cosmos-sdk/x/bank/types"
+)
+
+const (
+	DefaultCoreMsgGasUsage = 21000
+	DefaultGasPrice        = 120000
+	TestDenom              = "acoin"
+)
+
+// TestGasRefundGas tests the refund gas exclusively without going though the state transition
+// The gas part on the name refers to the file name to not generate a duplicated test name
+func (suite *KeeperTestSuite) TestGasRefundGas() {
+	// FeeCollector account is pre-funded with enough tokens
+	// for refund to work
+	// NOTE: everything should happen within the same block for
+	// feecollector account to remain funded
+	baseDenom := types.GetEVMCoinDenom()
+
+	coins := sdk.NewCoins(
+		sdk.NewCoin(
+			baseDenom,
+			sdkmath.NewInt(6e18),
+		),
+		sdk.NewCoin(
+			TestDenom,
+			sdkmath.NewInt(6e18),
+		),
+	)
+	feeAddress := authtypes.NewModuleAddress(authtypes.FeeCollectorName)
+
+	balances := []banktypes.Balance{
+		{
+			Address: feeAddress.String(),
+			Coins:   coins,
+		},
+	}
+	bankGenesis := banktypes.DefaultGenesisState()
+	bankGenesis.Balances = balances
+	customGenesis := network.CustomGenesisState{}
+	customGenesis[banktypes.ModuleName] = bankGenesis
+
+	// Create a txFactory
+	keyring := testkeyring.New(2)
+	unitNetwork := network.NewUnitTestNetwork(
+		suite.Create,
+		network.WithPreFundedAccounts(keyring.GetAllAccAddrs()...),
+		network.WithCustomGenesis(customGenesis),
+	)
+	grpcHandler := grpc.NewIntegrationHandler(unitNetwork)
+	txFactory := factory.New(unitNetwork, grpcHandler)
+
+	// Create a core message to use for the test
+	sender := keyring.GetKey(0)
+	recipient := keyring.GetAddr(1)
+	coreMsg, err := txFactory.GenerateGethCoreMsg(
+		sender.Priv,
+		types.EvmTxArgs{
+			To:       &recipient,
+			Amount:   big.NewInt(100),
+			GasPrice: big.NewInt(DefaultGasPrice),
+		},
+	)
+	suite.Require().NoError(err)
+
+	// Produce all the test cases
+	testCases := []struct {
+		name           string
+		leftoverGas    uint64 // The coreMsg always uses 21000 gas limit
+		malleate       func(sdk.Context) sdk.Context
+		expectedRefund sdk.Coins
+		errContains    string
+	}{
+		{
+			name:        "Refund the full value as no gas was used",
+			leftoverGas: DefaultCoreMsgGasUsage,
+			expectedRefund: sdk.NewCoins(
+				sdk.NewCoin(baseDenom, sdkmath.NewInt(DefaultCoreMsgGasUsage*DefaultGasPrice)),
+			),
+		},
+		{
+			name:        "Refund half the value as half gas was used",
+			leftoverGas: DefaultCoreMsgGasUsage / 2,
+			expectedRefund: sdk.NewCoins(
+				sdk.NewCoin(baseDenom, sdkmath.NewInt((DefaultCoreMsgGasUsage*DefaultGasPrice)/2)),
+			),
+		},
+		{
+			name:        "No refund as no gas was left over used",
+			leftoverGas: 0,
+			expectedRefund: sdk.NewCoins(
+				sdk.NewCoin(baseDenom, sdkmath.NewInt(0)),
+			),
+		},
+		{
+			name:        "Refund with context fees, refunding the full value",
+			leftoverGas: DefaultCoreMsgGasUsage,
+			malleate: func(ctx sdk.Context) sdk.Context {
+				// Set the fee abstraction paid fee key with a single coin
+				return ctx.WithValue(
+					keeper.ContextPaidFeesKey{},
+					sdk.NewCoins(
+						sdk.NewCoin(TestDenom, sdkmath.NewInt(750_000_000)),
+					),
+				)
+			},
+			expectedRefund: sdk.NewCoins(
+				sdk.NewCoin(TestDenom, sdkmath.NewInt(750_000_000)),
+			),
+		},
+		{
+			name:        "Refund with context fees, refunding the half the value",
+			leftoverGas: DefaultCoreMsgGasUsage / 2,
+			malleate: func(ctx sdk.Context) sdk.Context {
+				// Set the fee abstraction paid fee key with a single coin
+				return ctx.WithValue(
+					keeper.ContextPaidFeesKey{},
+					sdk.NewCoins(
+						sdk.NewCoin(TestDenom, sdkmath.NewInt(750_000_000)),
+					),
+				)
+			},
+			expectedRefund: sdk.NewCoins(
+				sdk.NewCoin(TestDenom, sdkmath.NewInt(750_000_000/2)),
+			),
+		},
+		{
+			name:        "Refund with context fees, no refund",
+			leftoverGas: 0,
+			malleate: func(ctx sdk.Context) sdk.Context {
+				// Set the fee abstraction paid fee key with a single coin
+				return ctx.WithValue(
+					keeper.ContextPaidFeesKey{},
+					sdk.NewCoins(
+						sdk.NewCoin(TestDenom, sdkmath.NewInt(750_000_000)),
+					),
+				)
+			},
+			expectedRefund: sdk.NewCoins(
+				sdk.NewCoin(TestDenom, sdkmath.NewInt(0)),
+			),
+		},
+		{
+			name:        "Error - More than one coin being passed",
+			leftoverGas: DefaultCoreMsgGasUsage,
+			malleate: func(ctx sdk.Context) sdk.Context {
+				// Set the fee abstraction paid fee key with a single coin
+				return ctx.WithValue(
+					keeper.ContextPaidFeesKey{},
+					sdk.NewCoins(
+						sdk.NewCoin(TestDenom, sdkmath.NewInt(750_000_000)),
+						sdk.NewCoin("atwo", sdkmath.NewInt(750_000_000)),
+					),
+				)
+			},
+			errContains: "expected a single coin for EVM refunds, got 2",
+		},
+	}
+
+	// Iterate though the test cases
+	for _, tc := range testCases {
+		suite.Run(tc.name, func() {
+			// Generate a cached context to not leak data between tests
+			ctx, _ := unitNetwork.GetContext().CacheContext()
+
+			// Apply the malleate function to the context
+			if tc.malleate != nil {
+				ctx = tc.malleate(ctx)
+			}
+
+			if tc.leftoverGas > DefaultCoreMsgGasUsage {
+				return
+			}
+
+			initialBalances := unitNetwork.App.GetBankKeeper().GetAllBalances(ctx, feeAddress)
+
+			err = unitNetwork.App.GetEVMKeeper().RefundGas(
+				ctx,
+				*coreMsg,
+				tc.leftoverGas,
+				DefaultCoreMsgGasUsage,
+				baseDenom,
+			)
+
+			// Check the error
+			if tc.errContains != "" {
+				suite.Require().ErrorContains(err, tc.errContains, "RefundGas should return an error")
+			} else {
+				suite.Require().NoError(err, "RefundGas should not return an error")
+			}
+
+			// Check the balance change
+			if !tc.expectedRefund.Empty() {
+				diff := initialBalances.Sub(unitNetwork.App.GetBankKeeper().GetAllBalances(ctx, feeAddress)...)
+				for _, coin := range tc.expectedRefund {
+					suite.Require().Equal(coin.Amount, diff.AmountOf(coin.Denom))
+				}
+			}
+		})
+	}
+}

tests/integration/x/vm/test_state_transition.go

@@ -488,6 +488,7 @@ func (s *KeeperTestSuite) TestRefundGas() {
 				unitNetwork.GetContext(),
 				*coreMsg,
 				refund,
+				gasUsed,
 				unitNetwork.GetBaseDenom(),
 			)
 

x/vm/keeper/gas.go

@@ -16,6 +16,9 @@ import (
 	authtypes "github.com/cosmos/cosmos-sdk/x/auth/types"
 )
 
+// ContextPaidFeesKey is a key used to store the paid fee in the context
+type ContextPaidFeesKey struct{}
+
 // GetEthIntrinsicGas returns the intrinsic gas cost for the transaction
 func (k *Keeper) GetEthIntrinsicGas(ctx sdk.Context, msg core.Message, cfg *params.ChainConfig,
 	isContractCreation bool,
@@ -32,26 +35,59 @@ func (k *Keeper) GetEthIntrinsicGas(ctx sdk.Context, msg core.Message, cfg *para
 // consumed in the transaction. Additionally, the function sets the total gas consumed to the value
 // returned by the EVM execution, thus ignoring the previous intrinsic gas consumed during in the
 // AnteHandler.
-func (k *Keeper) RefundGas(ctx sdk.Context, msg core.Message, leftoverGas uint64, denom string) error {
+func (k *Keeper) RefundGas(ctx sdk.Context, msg core.Message, leftoverGas uint64, gasUsed uint64, denom string) error {
 	// Return EVM tokens for remaining gas, exchanged at the original rate.
 	remaining := new(big.Int).Mul(new(big.Int).SetUint64(leftoverGas), msg.GasPrice)
 
+	// Check if gas is zero
+	if gasUsed == 0 {
+		// If gas is zero, we cannot refund anything, so we return early
+		return nil
+	}
+
 	switch remaining.Sign() {
 	case -1:
 		// negative refund errors
 		return errorsmod.Wrapf(types.ErrInvalidRefund, "refunded amount value cannot be negative %d", remaining.Int64())
 	case 1:
-		// positive amount refund
+		// Attempt to extract the paid coin from the context
+		// This is used when fee abstraction is applied into the fee payment
+		// If no value is found under the context, the original denom is used
+		if val := ctx.Value(ContextPaidFeesKey{}); val != nil {
+			// We check if a coin exists under the value and if it's not empty
+			if paidCoins, ok := val.(sdk.Coins); ok && !paidCoins.IsZero() {
+				// We know that only a single coin is used for EVM payments
+				if len(paidCoins) != 1 {
+					// This should never happen, but if it does, we return an error
+					return errorsmod.Wrapf(types.ErrInvalidRefund, "expected a single coin for EVM refunds, got %d", len(paidCoins))
+				}
+				paidCoin := paidCoins[0]
+
+				// Extract the coin information
+				denom = paidCoin.Denom
+				amount := paidCoin.Amount.BigInt()
+
+				// Calculate the amount to refund
+				// This is calculated as:
+				// remaining = amount * leftoverGas / gasUsed
+				remaining = new(big.Int).Div(
+					new(big.Int).Mul(amount, new(big.Int).SetUint64(leftoverGas)),
+					new(big.Int).SetUint64(gasUsed),
+				)
+			}
+		}
+
+		// Positive amount refund
 		refundedCoins := sdk.Coins{sdk.NewCoin(denom, sdkmath.NewIntFromBigInt(remaining))}
 
-		// refund to sender from the fee collector module account, which is the escrow account in charge of collecting tx fees
+		// Refund to sender from the fee collector module account, which is the escrow account in charge of collecting tx fees
 		err := k.bankWrapper.SendCoinsFromModuleToAccount(ctx, authtypes.FeeCollectorName, msg.From.Bytes(), refundedCoins)
 		if err != nil {
 			err = errorsmod.Wrapf(errortypes.ErrInsufficientFunds, "fee collector account failed to refund fees: %s", err.Error())
 			return errorsmod.Wrapf(err, "failed to refund %d leftover gas (%s)", leftoverGas, refundedCoins.String())
 		}
 	default:
-		// no refund, consume gas and update the tx gas meter
+		// No refund, consume gas and update the tx gas meter
 	}
 
 	return nil

x/vm/keeper/state_transition.go

@@ -311,7 +311,7 @@ func (k *Keeper) ApplyTransaction(ctx sdk.Context, tx *ethtypes.Transaction) (*t
 	if msg.GasLimit > res.GasUsed {
 		remainingGas = msg.GasLimit - res.GasUsed
 	}
-	if err = k.RefundGas(ctx, *msg, remainingGas, types.GetEVMCoinDenom()); err != nil {
+	if err = k.RefundGas(ctx, *msg, remainingGas, res.GasUsed, types.GetEVMCoinDenom()); err != nil {
 		return nil, errorsmod.Wrapf(err, "failed to refund gas leftover gas to sender %s", msg.From)
 	}