Migrate fee payment from Currency to fungible (#2292)

Part of #226 
Related #1833

- Deprecate `CurrencyAdapter` and introduce `FungibleAdapter`
- Deprecate `ToStakingPot` and replace usage with `ResolveTo`
- Required creating a new `StakingPotAccountId` struct that implements
`TypedGet` for the staking pot account ID
- Update parachain common utils `DealWithFees`, `ToAuthor` and
`AssetsToBlockAuthor` implementations to use `fungible`
- Update runtime XCM Weight Traders to use `ResolveTo` instead of
`ToStakingPot`
- Update runtime Transaction Payment pallets to use `FungibleAdapter`
instead of `CurrencyAdapter`
- [x] Blocked by #1296,
needs the `Unbalanced::decrease_balance` fix

bridges/bin/runtime-common/src/mock.rs

@@ -166,7 +166,7 @@ impl pallet_balances::Config for TestRuntime {
 
 #[derive_impl(pallet_transaction_payment::config_preludes::TestDefaultConfig)]
 impl pallet_transaction_payment::Config for TestRuntime {
-	type OnChargeTransaction = pallet_transaction_payment::CurrencyAdapter<Balances, ()>;
+	type OnChargeTransaction = pallet_transaction_payment::FungibleAdapter<Balances, ()>;
 	type OperationalFeeMultiplier = ConstU8<5>;
 	type WeightToFee = IdentityFee<ThisChainBalance>;
 	type LengthToFee = ConstantMultiplier<ThisChainBalance, TransactionByteFee>;

cumulus/pallets/collator-selection/src/lib.rs

@@ -81,6 +81,8 @@
 
 #![cfg_attr(not(feature = "std"), no_std)]
 
+use core::marker::PhantomData;
+use frame_support::traits::TypedGet;
 pub use pallet::*;
 
 #[cfg(test)]
@@ -981,3 +983,15 @@ pub mod pallet {
 		}
 	}
 }
+
+/// [`TypedGet`] implementaion to get the AccountId of the StakingPot.
+pub struct StakingPotAccountId<R>(PhantomData<R>);
+impl<R> TypedGet for StakingPotAccountId<R>
+where
+	R: crate::Config,
+{
+	type Type = <R as frame_system::Config>::AccountId;
+	fn get() -> Self::Type {
+		<crate::Pallet<R>>::account_id()
+	}
+}

cumulus/parachains/common/src/impls.rs

@@ -17,10 +17,11 @@
 //! Taken from polkadot/runtime/common (at a21cd64) and adapted for parachains.
 
 use frame_support::traits::{
-	fungibles::{self, Balanced, Credit},
-	Contains, ContainsPair, Currency, Get, Imbalance, OnUnbalanced, OriginTrait,
+	fungible, fungibles, tokens::imbalance::ResolveTo, Contains, ContainsPair, Currency, Defensive,
+	Get, Imbalance, OnUnbalanced, OriginTrait,
 };
 use pallet_asset_tx_payment::HandleCredit;
+use pallet_collator_selection::StakingPotAccountId;
 use sp_runtime::traits::Zero;
 use sp_std::{marker::PhantomData, prelude::*};
 use xcm::latest::{
@@ -29,16 +30,20 @@ use xcm::latest::{
 };
 use xcm_executor::traits::ConvertLocation;
 
+/// Type alias to conveniently refer to `frame_system`'s `Config::AccountId`.
+pub type AccountIdOf<T> = <T as frame_system::Config>::AccountId;
+
 /// Type alias to conveniently refer to the `Currency::NegativeImbalance` associated type.
 pub type NegativeImbalance<T> = <pallet_balances::Pallet<T> as Currency<
 	<T as frame_system::Config>::AccountId,
 >>::NegativeImbalance;
 
-/// Type alias to conveniently refer to `frame_system`'s `Config::AccountId`.
-pub type AccountIdOf<R> = <R as frame_system::Config>::AccountId;
-
 /// Implementation of `OnUnbalanced` that deposits the fees into a staking pot for later payout.
+#[deprecated(
+	note = "ToStakingPot is deprecated and will be removed after March 2024. Please use frame_support::traits::tokens::imbalance::ResolveTo instead."
+)]
 pub struct ToStakingPot<R>(PhantomData<R>);
+#[allow(deprecated)]
 impl<R> OnUnbalanced<NegativeImbalance<R>> for ToStakingPot<R>
 where
 	R: pallet_balances::Config + pallet_collator_selection::Config,
@@ -47,25 +52,30 @@ where
 {
 	fn on_nonzero_unbalanced(amount: NegativeImbalance<R>) {
 		let staking_pot = <pallet_collator_selection::Pallet<R>>::account_id();
+		// In case of error: Will drop the result triggering the `OnDrop` of the imbalance.
 		<pallet_balances::Pallet<R>>::resolve_creating(&staking_pot, amount);
 	}
 }
 
-/// Implementation of `OnUnbalanced` that deals with the fees by combining tip and fee and passing
-/// the result on to `ToStakingPot`.
+/// Fungible implementation of `OnUnbalanced` that deals with the fees by combining tip and fee and
+/// passing the result on to `ToStakingPot`.
 pub struct DealWithFees<R>(PhantomData<R>);
-impl<R> OnUnbalanced<NegativeImbalance<R>> for DealWithFees<R>
+impl<R> OnUnbalanced<fungible::Credit<R::AccountId, pallet_balances::Pallet<R>>> for DealWithFees<R>
 where
 	R: pallet_balances::Config + pallet_collator_selection::Config,
 	AccountIdOf<R>: From<polkadot_primitives::AccountId> + Into<polkadot_primitives::AccountId>,
 	<R as frame_system::Config>::RuntimeEvent: From<pallet_balances::Event<R>>,
 {
-	fn on_unbalanceds<B>(mut fees_then_tips: impl Iterator<Item = NegativeImbalance<R>>) {
+	fn on_unbalanceds<B>(
+		mut fees_then_tips: impl Iterator<
+			Item = fungible::Credit<R::AccountId, pallet_balances::Pallet<R>>,
+		>,
+	) {
 		if let Some(mut fees) = fees_then_tips.next() {
 			if let Some(tips) = fees_then_tips.next() {
 				tips.merge_into(&mut fees);
 			}
-			<ToStakingPot<R> as OnUnbalanced<_>>::on_unbalanced(fees);
+			ResolveTo::<StakingPotAccountId<R>, pallet_balances::Pallet<R>>::on_unbalanced(fees)
 		}
 	}
 }
@@ -79,10 +89,11 @@ where
 	R: pallet_authorship::Config + pallet_assets::Config<I>,
 	AccountIdOf<R>: From<polkadot_primitives::AccountId> + Into<polkadot_primitives::AccountId>,
 {
-	fn handle_credit(credit: Credit<AccountIdOf<R>, pallet_assets::Pallet<R, I>>) {
+	fn handle_credit(credit: fungibles::Credit<AccountIdOf<R>, pallet_assets::Pallet<R, I>>) {
+		use frame_support::traits::fungibles::Balanced;
 		if let Some(author) = pallet_authorship::Pallet::<R>::author() {
 			// In case of error: Will drop the result triggering the `OnDrop` of the imbalance.
-			let _ = pallet_assets::Pallet::<R, I>::resolve(&author, credit);
+			let _ = pallet_assets::Pallet::<R, I>::resolve(&author, credit).defensive();
 		}
 	}
 }
@@ -313,8 +324,14 @@ mod tests {
 	#[test]
 	fn test_fees_and_tip_split() {
 		new_test_ext().execute_with(|| {
-			let fee = Balances::issue(10);
-			let tip = Balances::issue(20);
+			let fee =
+				<pallet_balances::Pallet<Test> as frame_support::traits::fungible::Balanced<
+					AccountId,
+				>>::issue(10);
+			let tip =
+				<pallet_balances::Pallet<Test> as frame_support::traits::fungible::Balanced<
+					AccountId,
+				>>::issue(20);
 
 			assert_eq!(Balances::free_balance(TEST_ACCOUNT), 0);
 

cumulus/parachains/runtimes/assets/asset-hub-rococo/src/lib.rs

@@ -226,7 +226,7 @@ parameter_types! {
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type OnChargeTransaction =
-		pallet_transaction_payment::CurrencyAdapter<Balances, DealWithFees<Runtime>>;
+		pallet_transaction_payment::FungibleAdapter<Balances, DealWithFees<Runtime>>;
 	type WeightToFee = WeightToFee;
 	type LengthToFee = ConstantMultiplier<Balance, TransactionByteFee>;
 	type FeeMultiplierUpdate = SlowAdjustingFeeUpdate<Self>;

cumulus/parachains/runtimes/assets/asset-hub-rococo/src/xcm_config.rs

@@ -27,14 +27,13 @@ use assets_common::{
 use frame_support::{
 	parameter_types,
 	traits::{
-		tokens::imbalance::ResolveAssetTo, ConstU32, Contains, Equals, Everything, Nothing,
-		PalletInfoAccess,
+		tokens::imbalance::{ResolveAssetTo, ResolveTo},
+		ConstU32, Contains, Equals, Everything, Nothing, PalletInfoAccess,
 	},
 };
 use frame_system::EnsureRoot;
 use pallet_xcm::XcmPassthrough;
 use parachains_common::{
-	impls::ToStakingPot,
 	xcm_config::{
 		AllSiblingSystemParachains, AssetFeeAsExistentialDepositMultiplier,
 		ConcreteAssetFromSystem, ParentRelayOrSiblingParachains, RelayOrOtherSystemParachains,
@@ -569,7 +568,13 @@ impl xcm_executor::Config for XcmConfig {
 		MaxInstructions,
 	>;
 	type Trader = (
-		UsingComponents<WeightToFee, TokenLocation, AccountId, Balances, ToStakingPot<Runtime>>,
+		UsingComponents<
+			WeightToFee,
+			TokenLocation,
+			AccountId,
+			Balances,
+			ResolveTo<StakingPot, Balances>,
+		>,
 		cumulus_primitives_utility::SwapFirstAssetTrader<
 			TokenLocationV3,
 			crate::AssetConversion,

cumulus/parachains/runtimes/assets/asset-hub-westend/src/lib.rs

@@ -210,7 +210,7 @@ parameter_types! {
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type OnChargeTransaction =
-		pallet_transaction_payment::CurrencyAdapter<Balances, DealWithFees<Runtime>>;
+		pallet_transaction_payment::FungibleAdapter<Balances, DealWithFees<Runtime>>;
 	type WeightToFee = WeightToFee;
 	type LengthToFee = ConstantMultiplier<Balance, TransactionByteFee>;
 	type FeeMultiplierUpdate = SlowAdjustingFeeUpdate<Self>;

cumulus/parachains/runtimes/assets/asset-hub-westend/src/xcm_config.rs

@@ -27,14 +27,13 @@ use assets_common::{
 use frame_support::{
 	parameter_types,
 	traits::{
-		tokens::imbalance::ResolveAssetTo, ConstU32, Contains, Equals, Everything, Nothing,
-		PalletInfoAccess,
+		tokens::imbalance::{ResolveAssetTo, ResolveTo},
+		ConstU32, Contains, Equals, Everything, Nothing, PalletInfoAccess,
 	},
 };
 use frame_system::EnsureRoot;
 use pallet_xcm::XcmPassthrough;
 use parachains_common::{
-	impls::ToStakingPot,
 	xcm_config::{
 		AllSiblingSystemParachains, AssetFeeAsExistentialDepositMultiplier,
 		ConcreteAssetFromSystem, RelayOrOtherSystemParachains,
@@ -591,7 +590,13 @@ impl xcm_executor::Config for XcmConfig {
 		MaxInstructions,
 	>;
 	type Trader = (
-		UsingComponents<WeightToFee, WestendLocation, AccountId, Balances, ToStakingPot<Runtime>>,
+		UsingComponents<
+			WeightToFee,
+			WestendLocation,
+			AccountId,
+			Balances,
+			ResolveTo<StakingPot, Balances>,
+		>,
 		cumulus_primitives_utility::SwapFirstAssetTrader<
 			WestendLocationV3,
 			crate::AssetConversion,

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-rococo/src/lib.rs

@@ -317,7 +317,7 @@ parameter_types! {
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type OnChargeTransaction =
-		pallet_transaction_payment::CurrencyAdapter<Balances, DealWithFees<Runtime>>;
+		pallet_transaction_payment::FungibleAdapter<Balances, DealWithFees<Runtime>>;
 	type OperationalFeeMultiplier = ConstU8<5>;
 	type WeightToFee = WeightToFee;
 	type LengthToFee = ConstantMultiplier<Balance, TransactionByteFee>;

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-rococo/src/xcm_config.rs

@@ -33,13 +33,13 @@ use bp_relayers::{PayRewardFromAccount, RewardsAccountOwner, RewardsAccountParam
 use bp_runtime::ChainId;
 use frame_support::{
 	parameter_types,
-	traits::{ConstU32, Contains, Equals, Everything, Nothing},
+	traits::{tokens::imbalance::ResolveTo, ConstU32, Contains, Equals, Everything, Nothing},
 	StoragePrefixedMap,
 };
 use frame_system::EnsureRoot;
+use pallet_collator_selection::StakingPotAccountId;
 use pallet_xcm::XcmPassthrough;
 use parachains_common::{
-	impls::ToStakingPot,
 	xcm_config::{
 		AllSiblingSystemParachains, ConcreteAssetFromSystem, ParentRelayOrSiblingParachains,
 		RelayOrOtherSystemParachains,
@@ -295,8 +295,13 @@ impl xcm_executor::Config for XcmConfig {
 		RuntimeCall,
 		MaxInstructions,
 	>;
-	type Trader =
-		UsingComponents<WeightToFee, TokenLocation, AccountId, Balances, ToStakingPot<Runtime>>;
+	type Trader = UsingComponents<
+		WeightToFee,
+		TokenLocation,
+		AccountId,
+		Balances,
+		ResolveTo<StakingPotAccountId<Runtime>, Balances>,
+	>;
 	type ResponseHandler = PolkadotXcm;
 	type AssetTrap = PolkadotXcm;
 	type AssetLocker = ();

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-westend/src/lib.rs

@@ -291,7 +291,7 @@ parameter_types! {
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type OnChargeTransaction =
-		pallet_transaction_payment::CurrencyAdapter<Balances, DealWithFees<Runtime>>;
+		pallet_transaction_payment::FungibleAdapter<Balances, DealWithFees<Runtime>>;
 	type OperationalFeeMultiplier = ConstU8<5>;
 	type WeightToFee = WeightToFee;
 	type LengthToFee = ConstantMultiplier<Balance, TransactionByteFee>;

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-westend/src/xcm_config.rs

@@ -22,12 +22,12 @@ use super::{
 use crate::bridge_common_config::{DeliveryRewardInBalance, RequiredStakeForStakeAndSlash};
 use frame_support::{
 	parameter_types,
-	traits::{ConstU32, Contains, Equals, Everything, Nothing},
+	traits::{tokens::imbalance::ResolveTo, ConstU32, Contains, Equals, Everything, Nothing},
 };
 use frame_system::EnsureRoot;
+use pallet_collator_selection::StakingPotAccountId;
 use pallet_xcm::XcmPassthrough;
 use parachains_common::{
-	impls::ToStakingPot,
 	xcm_config::{
 		AllSiblingSystemParachains, ConcreteAssetFromSystem, ParentRelayOrSiblingParachains,
 		RelayOrOtherSystemParachains,
@@ -244,8 +244,13 @@ impl xcm_executor::Config for XcmConfig {
 		RuntimeCall,
 		MaxInstructions,
 	>;
-	type Trader =
-		UsingComponents<WeightToFee, WestendLocation, AccountId, Balances, ToStakingPot<Runtime>>;
+	type Trader = UsingComponents<
+		WeightToFee,
+		WestendLocation,
+		AccountId,
+		Balances,
+		ResolveTo<StakingPotAccountId<Runtime>, Balances>,
+	>;
 	type ResponseHandler = PolkadotXcm;
 	type AssetTrap = PolkadotXcm;
 	type AssetLocker = ();

cumulus/parachains/runtimes/collectives/collectives-westend/src/lib.rs

@@ -223,7 +223,7 @@ parameter_types! {
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type OnChargeTransaction =
-		pallet_transaction_payment::CurrencyAdapter<Balances, DealWithFees<Runtime>>;
+		pallet_transaction_payment::FungibleAdapter<Balances, DealWithFees<Runtime>>;
 	type WeightToFee = WeightToFee;
 	type LengthToFee = ConstantMultiplier<Balance, TransactionByteFee>;
 	type FeeMultiplierUpdate = SlowAdjustingFeeUpdate<Self>;

cumulus/parachains/runtimes/collectives/collectives-westend/src/xcm_config.rs

@@ -20,17 +20,15 @@ use super::{
 };
 use frame_support::{
 	parameter_types,
-	traits::{ConstU32, Contains, Equals, Everything, Nothing},
+	traits::{tokens::imbalance::ResolveTo, ConstU32, Contains, Equals, Everything, Nothing},
 	weights::Weight,
 };
 use frame_system::EnsureRoot;
+use pallet_collator_selection::StakingPotAccountId;
 use pallet_xcm::XcmPassthrough;
-use parachains_common::{
-	impls::ToStakingPot,
-	xcm_config::{
-		AllSiblingSystemParachains, ConcreteAssetFromSystem, ParentRelayOrSiblingParachains,
-		RelayOrOtherSystemParachains,
-	},
+use parachains_common::xcm_config::{
+	AllSiblingSystemParachains, ConcreteAssetFromSystem, ParentRelayOrSiblingParachains,
+	RelayOrOtherSystemParachains,
 };
 use polkadot_parachain_primitives::primitives::Sibling;
 use polkadot_runtime_common::xcm_sender::ExponentialPrice;
@@ -268,8 +266,13 @@ impl xcm_executor::Config for XcmConfig {
 	type UniversalLocation = UniversalLocation;
 	type Barrier = Barrier;
 	type Weigher = FixedWeightBounds<TempFixedXcmWeight, RuntimeCall, MaxInstructions>;
-	type Trader =
-		UsingComponents<WeightToFee, WndLocation, AccountId, Balances, ToStakingPot<Runtime>>;
+	type Trader = UsingComponents<
+		WeightToFee,
+		WndLocation,
+		AccountId,
+		Balances,
+		ResolveTo<StakingPotAccountId<Runtime>, Balances>,
+	>;
 	type ResponseHandler = PolkadotXcm;
 	type AssetTrap = PolkadotXcm;
 	type AssetClaims = PolkadotXcm;

cumulus/parachains/runtimes/contracts/contracts-rococo/src/lib.rs

@@ -232,7 +232,7 @@ parameter_types! {
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type OnChargeTransaction =
-		pallet_transaction_payment::CurrencyAdapter<Balances, DealWithFees<Runtime>>;
+		pallet_transaction_payment::FungibleAdapter<Balances, DealWithFees<Runtime>>;
 	type WeightToFee = WeightToFee;
 	/// Relay Chain `TransactionByteFee` / 10
 	type LengthToFee = ConstantMultiplier<Balance, TransactionByteFee>;

cumulus/parachains/runtimes/coretime/coretime-rococo/src/lib.rs

@@ -244,7 +244,7 @@ parameter_types! {
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type OnChargeTransaction =
-		pallet_transaction_payment::CurrencyAdapter<Balances, DealWithFees<Runtime>>;
+		pallet_transaction_payment::FungibleAdapter<Balances, DealWithFees<Runtime>>;
 	type OperationalFeeMultiplier = ConstU8<5>;
 	type WeightToFee = WeightToFee;
 	type LengthToFee = ConstantMultiplier<Balance, TransactionByteFee>;

cumulus/parachains/runtimes/coretime/coretime-rococo/src/xcm_config.rs

@@ -22,12 +22,12 @@ use super::{
 use frame_support::{
 	pallet_prelude::PalletInfoAccess,
 	parameter_types,
-	traits::{ConstU32, Contains, Equals, Everything, Nothing},
+	traits::{tokens::imbalance::ResolveTo, ConstU32, Contains, Equals, Everything, Nothing},
 };
 use frame_system::EnsureRoot;
+use pallet_collator_selection::StakingPotAccountId;
 use pallet_xcm::XcmPassthrough;
 use parachains_common::{
-	impls::ToStakingPot,
 	xcm_config::{
 		AllSiblingSystemParachains, ConcreteAssetFromSystem, ParentRelayOrSiblingParachains,
 		RelayOrOtherSystemParachains,
@@ -237,8 +237,13 @@ impl xcm_executor::Config for XcmConfig {
 		RuntimeCall,
 		MaxInstructions,
 	>;
-	type Trader =
-		UsingComponents<WeightToFee, RocRelayLocation, AccountId, Balances, ToStakingPot<Runtime>>;
+	type Trader = UsingComponents<
+		WeightToFee,
+		RocRelayLocation,
+		AccountId,
+		Balances,
+		ResolveTo<StakingPotAccountId<Runtime>, Balances>,
+	>;
 	type ResponseHandler = PolkadotXcm;
 	type AssetTrap = PolkadotXcm;
 	type AssetClaims = PolkadotXcm;