Fix/evm fee burning

primitives/src/evm.rs

@@ -18,11 +18,18 @@
 
 use crate::{AccountId, AssetId};
 
-use frame_support::ensure;
-use pallet_evm::{AddressMapping, HashedAddressMapping};
+use frame_support::{
+    ensure,
+    traits::{
+        fungible::{Balanced, Credit},
+        tokens::{fungible::Inspect, imbalance::OnUnbalanced},
+    },
+};
+use pallet_evm::{AddressMapping, HashedAddressMapping, OnChargeEVMTransaction};
 use parity_scale_codec::{Decode, Encode, MaxEncodedLen};
 use scale_info::TypeInfo;
-use sp_core::{Hasher, H160, H256};
+use sp_core::{Hasher, H160, H256, U256};
+use sp_runtime::traits::UniqueSaturatedInto;
 use sp_std::marker::PhantomData;
 
 use pallet_assets::AssetsCallback;
@@ -139,3 +146,49 @@ impl<Address> UnifiedAddress<Address> {
         }
     }
 }
+
+/// Wrapper around the `EvmFungibleAdapter` from the `pallet-evm`.
+///
+/// While it provides most of the functionality we need,
+/// it doesn't allow the tip to be deposited into an arbitrary account.
+/// This adapter allows us to do that.
+///
+/// Two separate `OnUnbalanced` handers are used:
+/// - `UOF` for the fee
+/// - `OUT` for the tip
+pub struct EVMFungibleAdapterWrapper<F, OUF, OUT>(core::marker::PhantomData<(F, OUF, OUT)>);
+impl<T, F, OUF, OUT> OnChargeEVMTransaction<T> for EVMFungibleAdapterWrapper<F, OUF, OUT>
+where
+    T: pallet_evm::Config,
+    F: Balanced<T::AccountId>,
+    OUF: OnUnbalanced<Credit<T::AccountId, F>>,
+    OUT: OnUnbalanced<Credit<T::AccountId, F>>,
+    U256: UniqueSaturatedInto<<F as Inspect<<T as frame_system::Config>::AccountId>>::Balance>,
+{
+    // Kept type as Option to satisfy bound of Default
+    type LiquidityInfo = Option<Credit<T::AccountId, F>>;
+
+    fn withdraw_fee(who: &H160, fee: U256) -> Result<Self::LiquidityInfo, pallet_evm::Error<T>> {
+        pallet_evm::EVMFungibleAdapter::<F, OUF>::withdraw_fee(who, fee)
+    }
+
+    fn correct_and_deposit_fee(
+        who: &H160,
+        corrected_fee: U256,
+        base_fee: U256,
+        already_withdrawn: Self::LiquidityInfo,
+    ) -> Self::LiquidityInfo {
+        <pallet_evm::EVMFungibleAdapter::<F, OUF> as OnChargeEVMTransaction<T>>::correct_and_deposit_fee(
+            who,
+            corrected_fee,
+            base_fee,
+            already_withdrawn,
+        )
+    }
+
+    fn pay_priority_fee(tip: Self::LiquidityInfo) {
+        if let Some(tip) = tip {
+            OUT::on_unbalanceds(Some(tip).into_iter());
+        }
+    }
+}

runtime/astar/src/lib.rs

@@ -84,7 +84,7 @@ use astar_primitives::{
         AccountCheck as DappStakingAccountCheck, CycleConfiguration, DAppId, EraNumber,
         PeriodNumber, RankedTier, SmartContract, StandardTierSlots,
     },
-    evm::EvmRevertCodeHandler,
+    evm::{EVMFungibleAdapterWrapper, EvmRevertCodeHandler},
     governance::{
         CommunityCouncilCollectiveInst, CommunityCouncilMembershipInst, CommunityTreasuryInst,
         EnsureRootOrAllMainCouncil, EnsureRootOrAllTechnicalCommittee,
@@ -474,7 +474,7 @@ impl pallet_inflation::PayoutPerBlock<Credit<AccountId, Balances>> for Inflation
     }
 
     fn collators(reward: Credit<AccountId, Balances>) {
-        ToStakingPot::on_unbalanced(reward);
+        CollatorRewardPot::on_unbalanced(reward);
     }
 }
 
@@ -614,8 +614,8 @@ parameter_types! {
     pub TreasuryAccountId: AccountId = TreasuryPalletId::get().into_account_truncating();
 }
 
-pub struct ToStakingPot;
-impl OnUnbalanced<Credit<AccountId, Balances>> for ToStakingPot {
+pub struct CollatorRewardPot;
+impl OnUnbalanced<Credit<AccountId, Balances>> for CollatorRewardPot {
     fn on_nonzero_unbalanced(amount: Credit<AccountId, Balances>) {
         let staking_pot = PotId::get().into_account_truncating();
         let _ = Balances::resolve(&staking_pot, amount);
@@ -838,9 +838,13 @@ impl OnUnbalanced<Credit<AccountId, Balances>> for DealWithFees {
             drop(to_burn);
 
             // pay fees to collator
-            <ToStakingPot as OnUnbalanced<_>>::on_unbalanced(collator);
+            <CollatorRewardPot as OnUnbalanced<_>>::on_unbalanced(collator);
         }
     }
+
+    fn on_unbalanced(amount: Credit<AccountId, Balances>) {
+        Self::on_unbalanceds(Some(amount).into_iter());
+    }
 }
 
 impl pallet_transaction_payment::Config for Runtime {
@@ -946,7 +950,7 @@ impl pallet_evm::Config for Runtime {
     type PrecompilesType = Precompiles;
     type PrecompilesValue = PrecompilesValue;
     type ChainId = ChainId;
-    type OnChargeTransaction = pallet_evm::EVMFungibleAdapter<Balances, ToStakingPot>;
+    type OnChargeTransaction = EVMFungibleAdapterWrapper<Balances, DealWithFees, CollatorRewardPot>;
     type BlockGasLimit = BlockGasLimit;
     type Timestamp = Timestamp;
     type OnCreate = ();

runtime/shibuya/src/lib.rs

@@ -83,7 +83,7 @@ use astar_primitives::{
         AccountCheck as DappStakingAccountCheck, CycleConfiguration, DAppId, EraNumber,
         PeriodNumber, RankedTier, SmartContract, StandardTierSlots,
     },
-    evm::{EvmRevertCodeHandler, HashedDefaultMappings},
+    evm::{EVMFungibleAdapterWrapper, EvmRevertCodeHandler, HashedDefaultMappings},
     governance::{
         CommunityCouncilCollectiveInst, CommunityCouncilMembershipInst, CommunityTreasuryInst,
         EnsureRootOrAllMainCouncil, EnsureRootOrAllTechnicalCommittee,
@@ -497,7 +497,7 @@ impl pallet_inflation::PayoutPerBlock<Credit<AccountId, Balances>> for Inflation
     }
 
     fn collators(reward: Credit<AccountId, Balances>) {
-        ToStakingPot::on_unbalanced(reward);
+        CollatorRewardPot::on_unbalanced(reward);
     }
 }
 
@@ -638,8 +638,8 @@ parameter_types! {
     pub TreasuryAccountId: AccountId = TreasuryPalletId::get().into_account_truncating();
 }
 
-pub struct ToStakingPot;
-impl OnUnbalanced<Credit<AccountId, Balances>> for ToStakingPot {
+pub struct CollatorRewardPot;
+impl OnUnbalanced<Credit<AccountId, Balances>> for CollatorRewardPot {
     fn on_nonzero_unbalanced(amount: Credit<AccountId, Balances>) {
         let staking_pot = PotId::get().into_account_truncating();
         let _ = Balances::resolve(&staking_pot, amount);
@@ -834,9 +834,13 @@ impl OnUnbalanced<Credit<AccountId, Balances>> for DealWithFees {
             drop(to_burn);
 
             // pay fees to collator
-            <ToStakingPot as OnUnbalanced<_>>::on_unbalanced(collator);
+            <CollatorRewardPot as OnUnbalanced<_>>::on_unbalanced(collator);
         }
     }
+
+    fn on_unbalanced(amount: Credit<AccountId, Balances>) {
+        Self::on_unbalanceds(Some(amount).into_iter());
+    }
 }
 
 impl pallet_transaction_payment::Config for Runtime {
@@ -947,7 +951,7 @@ impl pallet_evm::Config for Runtime {
     // Ethereum-compatible chain_id:
     // * Shibuya: 81
     type ChainId = EVMChainId;
-    type OnChargeTransaction = pallet_evm::EVMFungibleAdapter<Balances, ToStakingPot>;
+    type OnChargeTransaction = EVMFungibleAdapterWrapper<Balances, DealWithFees, CollatorRewardPot>;
     type BlockGasLimit = BlockGasLimit;
     type Timestamp = Timestamp;
     type OnCreate = ();

runtime/shiden/src/lib.rs

@@ -80,7 +80,7 @@ use astar_primitives::{
         AccountCheck as DappStakingAccountCheck, CycleConfiguration, DAppId, EraNumber,
         PeriodNumber, RankedTier, SmartContract, TierSlots as TierSlotsFunc,
     },
-    evm::EvmRevertCodeHandler,
+    evm::{EVMFungibleAdapterWrapper, EvmRevertCodeHandler},
     governance::OracleMembershipInst,
     oracle::{CurrencyAmount, CurrencyId, DummyCombineData, Price},
     xcm::AssetLocationIdConverter,
@@ -462,7 +462,7 @@ impl pallet_inflation::PayoutPerBlock<Credit<AccountId, Balances>> for Inflation
     }
 
     fn collators(reward: Credit<AccountId, Balances>) {
-        ToStakingPot::on_unbalanced(reward);
+        CollatorRewardPot::on_unbalanced(reward);
     }
 }
 
@@ -601,8 +601,8 @@ parameter_types! {
     pub TreasuryAccountId: AccountId = TreasuryPalletId::get().into_account_truncating();
 }
 
-pub struct ToStakingPot;
-impl OnUnbalanced<Credit<AccountId, Balances>> for ToStakingPot {
+pub struct CollatorRewardPot;
+impl OnUnbalanced<Credit<AccountId, Balances>> for CollatorRewardPot {
     fn on_nonzero_unbalanced(amount: Credit<AccountId, Balances>) {
         let staking_pot = PotId::get().into_account_truncating();
         let _ = Balances::resolve(&staking_pot, amount);
@@ -813,9 +813,13 @@ impl OnUnbalanced<Credit<AccountId, Balances>> for DealWithFees {
             drop(to_burn);
 
             // pay fees to collator
-            <ToStakingPot as OnUnbalanced<_>>::on_unbalanced(collator);
+            <CollatorRewardPot as OnUnbalanced<_>>::on_unbalanced(collator);
         }
     }
+
+    fn on_unbalanced(amount: Credit<AccountId, Balances>) {
+        Self::on_unbalanceds(Some(amount).into_iter());
+    }
 }
 
 impl pallet_transaction_payment::Config for Runtime {
@@ -920,7 +924,7 @@ impl pallet_evm::Config for Runtime {
     type PrecompilesType = Precompiles;
     type PrecompilesValue = PrecompilesValue;
     type ChainId = ChainId;
-    type OnChargeTransaction = pallet_evm::EVMFungibleAdapter<Balances, ToStakingPot>;
+    type OnChargeTransaction = EVMFungibleAdapterWrapper<Balances, DealWithFees, CollatorRewardPot>;
     type BlockGasLimit = BlockGasLimit;
     type Timestamp = Timestamp;
     type OnCreate = ();

tests/integration/src/fees.rs

@@ -0,0 +1,86 @@
+// This file is part of Astar.
+
+// Copyright (C) Stake Technologies Pte.Ltd.
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+// Astar is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Astar is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Astar. If not, see <http://www.gnu.org/licenses/>.
+
+use crate::setup::*;
+
+use frame_support::traits::Currency;
+use pallet_evm::{AddressMapping, OnChargeEVMTransaction};
+use sp_core::{H160, U256};
+use sp_runtime::traits::AccountIdConversion;
+
+#[test]
+fn evm_fees_work() {
+    new_test_ext().execute_with(|| {
+        let address = H160::repeat_byte(0xbe);
+        let mapped_address =
+            <Runtime as pallet_evm::Config>::AddressMapping::into_account_id(address);
+        Balances::make_free_balance_be(&mapped_address, 1_000_000_000_000_000);
+
+        type EvmFeeHandler = <Runtime as pallet_evm::Config>::OnChargeTransaction;
+
+        // 0. Define init values
+        let (base_fee, tip, init_fee) = (500, 100, 1000);
+        let corrected_fee = base_fee + tip;
+
+        let pot_account = PotId::get().into_account_truncating();
+        let init_reward_pot = Balances::free_balance(&pot_account);
+        let init_total_issuance = Balances::total_issuance();
+
+        // 1. Withdraw some init fee
+        let result = <EvmFeeHandler as OnChargeEVMTransaction<Runtime>>::withdraw_fee(
+            &address,
+            U256::from(init_fee),
+        );
+        let already_withdrawn = result.expect("Account is funded, must succeed.");
+
+        // 2. Correct the charged fee
+        let calculated_tip =
+            <EvmFeeHandler as OnChargeEVMTransaction<Runtime>>::correct_and_deposit_fee(
+                &address,
+                U256::from(corrected_fee),
+                U256::from(base_fee),
+                already_withdrawn,
+            );
+        assert!(calculated_tip.is_some());
+
+        // The expectation is that 20% of the fee was deposited into the reward pot, and the rest was burned.
+        assert_eq!(
+            init_reward_pot + base_fee / 5,
+            Balances::free_balance(&pot_account)
+        );
+        assert_eq!(
+            init_total_issuance - base_fee / 5 * 4,
+            Balances::total_issuance()
+        );
+
+        // 3. Deposit the tip
+        let issuance = Balances::total_issuance();
+        let pot = Balances::free_balance(&pot_account);
+        <EvmFeeHandler as OnChargeEVMTransaction<Runtime>>::pay_priority_fee(calculated_tip);
+        assert_eq!(
+            issuance,
+            Balances::total_issuance(),
+            "Total issuance should not change since tip isn't burned."
+        );
+        assert_eq!(
+            pot + tip,
+            Balances::free_balance(&pot_account),
+            "Pot should increase by the tip amount."
+        );
+    })
+}

tests/integration/src/lib.rs

@@ -52,3 +52,6 @@ mod governance;
 
 #[cfg(any(feature = "shibuya", feature = "shiden", feature = "astar"))]
 mod xcm_api;
+
+#[cfg(any(feature = "shibuya", feature = "shiden", feature = "astar"))]
+mod fees;