Backported fee payment fix

substrate/bin/minimal/runtime/src/lib.rs

@@ -98,7 +98,7 @@ impl pallet_timestamp::Config for Runtime {}
 
 #[derive_impl(pallet_transaction_payment::config_preludes::TestDefaultConfig as pallet_transaction_payment::DefaultConfig)]
 impl pallet_transaction_payment::Config for Runtime {
-	type OnChargeTransaction = pallet_transaction_payment::CurrencyAdapter<Balances, ()>;
+	type OnChargeTransaction = pallet_transaction_payment::FungibleAdapter<Balances, ()>;
 	type WeightToFee = NoFee<<Self as pallet_balances::Config>::Balance>;
 	type LengthToFee = FixedFee<1, <Self as pallet_balances::Config>::Balance>;
 }

substrate/bin/node-template/runtime/src/lib.rs

@@ -40,7 +40,7 @@ pub use frame_support::{
 pub use frame_system::Call as SystemCall;
 pub use pallet_balances::Call as BalancesCall;
 pub use pallet_timestamp::Call as TimestampCall;
-use pallet_transaction_payment::{ConstFeeMultiplier, CurrencyAdapter, Multiplier};
+use pallet_transaction_payment::{ConstFeeMultiplier, FungibleAdapter, Multiplier};
 #[cfg(any(feature = "std", test))]
 pub use sp_runtime::BuildStorage;
 pub use sp_runtime::{Perbill, Permill};
@@ -236,7 +236,7 @@ parameter_types! {
 
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
-	type OnChargeTransaction = CurrencyAdapter<Balances, ()>;
+	type OnChargeTransaction = FungibleAdapter<Balances, ()>;
 	type OperationalFeeMultiplier = ConstU8<5>;
 	type WeightToFee = IdentityFee<Balance>;
 	type LengthToFee = IdentityFee<Balance>;

substrate/bin/node/runtime/src/lib.rs

@@ -70,6 +70,7 @@ use pallet_im_online::sr25519::AuthorityId as ImOnlineId;
 use pallet_nfts::PalletFeatures;
 use pallet_nis::WithMaximumOf;
 use pallet_session::historical as pallet_session_historical;
+#[allow(deprecated)]
 pub use pallet_transaction_payment::{CurrencyAdapter, Multiplier, TargetedFeeAdjustment};
 use pallet_transaction_payment::{FeeDetails, RuntimeDispatchInfo};
 use pallet_tx_pause::RuntimeCallNameOf;
@@ -544,6 +545,7 @@ parameter_types! {
 	pub MaximumMultiplier: Multiplier = Bounded::max_value();
 }
 
+#[allow(deprecated)]
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type OnChargeTransaction = CurrencyAdapter<Balances, DealWithFees>;

substrate/frame/balances/src/tests/mod.rs

@@ -32,7 +32,7 @@ use frame_support::{
 	weights::{IdentityFee, Weight},
 };
 use frame_system::{self as system, RawOrigin};
-use pallet_transaction_payment::{ChargeTransactionPayment, CurrencyAdapter, Multiplier};
+use pallet_transaction_payment::{ChargeTransactionPayment, FungibleAdapter, Multiplier};
 use scale_info::TypeInfo;
 use sp_core::{hexdisplay::HexDisplay, H256};
 use sp_io;
@@ -119,7 +119,7 @@ impl frame_system::Config for Test {
 
 impl pallet_transaction_payment::Config for Test {
 	type RuntimeEvent = RuntimeEvent;
-	type OnChargeTransaction = CurrencyAdapter<Pallet<Test>, ()>;
+	type OnChargeTransaction = FungibleAdapter<Pallet<Test>, ()>;
 	type OperationalFeeMultiplier = ConstU8<5>;
 	type WeightToFee = IdentityFee<u64>;
 	type LengthToFee = IdentityFee<u64>;

substrate/frame/executive/src/lib.rs

@@ -768,7 +768,7 @@ mod tests {
 	};
 	use frame_system::{ChainContext, LastRuntimeUpgrade, LastRuntimeUpgradeInfo};
 	use pallet_balances::Call as BalancesCall;
-	use pallet_transaction_payment::CurrencyAdapter;
+	use pallet_transaction_payment::FungibleAdapter;
 
 	const TEST_KEY: &[u8] = b":test:key:";
 
@@ -966,7 +966,7 @@ mod tests {
 	}
 	impl pallet_transaction_payment::Config for Runtime {
 		type RuntimeEvent = RuntimeEvent;
-		type OnChargeTransaction = CurrencyAdapter<Balances, ()>;
+		type OnChargeTransaction = FungibleAdapter<Balances, ()>;
 		type OperationalFeeMultiplier = ConstU8<5>;
 		type WeightToFee = IdentityFee<Balance>;
 		type LengthToFee = ConstantMultiplier<Balance, TransactionByteFee>;

substrate/frame/transaction-payment/asset-conversion-tx-payment/src/mock.rs

@@ -36,7 +36,7 @@ use frame_support::{
 use frame_system as system;
 use frame_system::{EnsureRoot, EnsureSignedBy};
 use pallet_asset_conversion::{Ascending, Chain, WithFirstAsset};
-use pallet_transaction_payment::CurrencyAdapter;
+use pallet_transaction_payment::FungibleAdapter;
 use sp_core::H256;
 use sp_runtime::{
 	traits::{AccountIdConversion, BlakeTwo256, IdentityLookup, SaturatedConversion},
@@ -170,7 +170,7 @@ impl OnUnbalanced<pallet_balances::NegativeImbalance<Runtime>> for DealWithFees
 
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
-	type OnChargeTransaction = CurrencyAdapter<Balances, DealWithFees>;
+	type OnChargeTransaction = FungibleAdapter<Balances, DealWithFees>;
 	type WeightToFee = WeightToFee;
 	type LengthToFee = TransactionByteFee;
 	type FeeMultiplierUpdate = ();

substrate/frame/transaction-payment/asset-tx-payment/src/mock.rs

@@ -28,7 +28,7 @@ use frame_support::{
 };
 use frame_system as system;
 use frame_system::EnsureRoot;
-use pallet_transaction_payment::CurrencyAdapter;
+use pallet_transaction_payment::FungibleAdapter;
 use sp_core::H256;
 use sp_runtime::traits::{BlakeTwo256, ConvertInto, IdentityLookup, SaturatedConversion};
 
@@ -138,7 +138,7 @@ impl WeightToFeeT for TransactionByteFee {
 
 impl pallet_transaction_payment::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
-	type OnChargeTransaction = CurrencyAdapter<Balances, ()>;
+	type OnChargeTransaction = FungibleAdapter<Balances, ()>;
 	type WeightToFee = WeightToFee;
 	type LengthToFee = TransactionByteFee;
 	type FeeMultiplierUpdate = ();

substrate/frame/transaction-payment/src/mock.rs

@@ -152,7 +152,7 @@ impl OnUnbalanced<pallet_balances::NegativeImbalance<Runtime>> for DealWithFees
 
 impl Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
-	type OnChargeTransaction = CurrencyAdapter<Balances, DealWithFees>;
+	type OnChargeTransaction = FungibleAdapter<Balances, DealWithFees>;
 	type OperationalFeeMultiplier = OperationalFeeMultiplier;
 	type WeightToFee = WeightToFee;
 	type LengthToFee = TransactionByteFee;

substrate/frame/transaction-payment/src/payment.rs

@@ -25,7 +25,11 @@ use sp_runtime::{
 use sp_std::marker::PhantomData;
 
 use frame_support::{
-	traits::{Currency, ExistenceRequirement, Imbalance, OnUnbalanced, WithdrawReasons},
+	traits::{
+		fungible::{Balanced, Credit, Debt, Inspect},
+		tokens::Precision,
+		Currency, ExistenceRequirement, Imbalance, OnUnbalanced, TryDrop, WithdrawReasons,
+	},
 	unsigned::TransactionValidityError,
 };
 
@@ -66,18 +70,90 @@ pub trait OnChargeTransaction<T: Config> {
 	) -> Result<(), TransactionValidityError>;
 }
 
-/// Implements the transaction payment for a pallet implementing the `Currency`
+/// Implements transaction payment for a pallet implementing the [`fungible`]
+/// trait (eg. pallet_balances) using an unbalance handler (implementing
+/// [`OnUnbalanced`]).
+///
+/// The unbalance handler is given 2 unbalanceds in [`OnUnbalanced::on_unbalanceds`]: `fee` and
+/// then `tip`.
+pub struct FungibleAdapter<F, OU>(PhantomData<(F, OU)>);
+
+impl<T, F, OU> OnChargeTransaction<T> for FungibleAdapter<F, OU>
+where
+	T: Config,
+	F: Balanced<T::AccountId>,
+	OU: OnUnbalanced<Credit<T::AccountId, F>>,
+{
+	type LiquidityInfo = Option<Credit<T::AccountId, F>>;
+	type Balance = <F as Inspect<<T as frame_system::Config>::AccountId>>::Balance;
+
+	fn withdraw_fee(
+		who: &<T>::AccountId,
+		_call: &<T>::RuntimeCall,
+		_dispatch_info: &DispatchInfoOf<<T>::RuntimeCall>,
+		fee: Self::Balance,
+		_tip: Self::Balance,
+	) -> Result<Self::LiquidityInfo, TransactionValidityError> {
+		if fee.is_zero() {
+			return Ok(None)
+		}
+
+		match F::withdraw(
+			who,
+			fee,
+			Precision::Exact,
+			frame_support::traits::tokens::Preservation::Preserve,
+			frame_support::traits::tokens::Fortitude::Polite,
+		) {
+			Ok(imbalance) => Ok(Some(imbalance)),
+			Err(_) => Err(InvalidTransaction::Payment.into()),
+		}
+	}
+
+	fn correct_and_deposit_fee(
+		who: &<T>::AccountId,
+		_dispatch_info: &DispatchInfoOf<<T>::RuntimeCall>,
+		_post_info: &PostDispatchInfoOf<<T>::RuntimeCall>,
+		corrected_fee: Self::Balance,
+		tip: Self::Balance,
+		already_withdrawn: Self::LiquidityInfo,
+	) -> Result<(), TransactionValidityError> {
+		if let Some(paid) = already_withdrawn {
+			// Calculate how much refund we should return
+			let refund_amount = paid.peek().saturating_sub(corrected_fee);
+			// refund to the the account that paid the fees. If this fails, the
+			// account might have dropped below the existential balance. In
+			// that case we don't refund anything.
+			let refund_imbalance = F::deposit(who, refund_amount, Precision::BestEffort)
+				.unwrap_or_else(|_| Debt::<T::AccountId, F>::zero());
+			// merge the imbalance caused by paying the fees and refunding parts of it again.
+			let adjusted_paid: Credit<T::AccountId, F> = paid
+				.offset(refund_imbalance)
+				.same()
+				.map_err(|_| TransactionValidityError::Invalid(InvalidTransaction::Payment))?;
+			// Call someone else to handle the imbalance (fee and tip separately)
+			let (tip, fee) = adjusted_paid.split(tip);
+			OU::on_unbalanceds(Some(fee).into_iter().chain(Some(tip)));
+		}
+
+		Ok(())
+	}
+}
+
+/// Implements the transaction payment for a pallet implementing the [`Currency`]
 /// trait (eg. the pallet_balances) using an unbalance handler (implementing
-/// `OnUnbalanced`).
+/// [`OnUnbalanced`]).
 ///
-/// The unbalance handler is given 2 unbalanceds in [`OnUnbalanced::on_unbalanceds`]: fee and
-/// then tip.
+/// The unbalance handler is given 2 unbalanceds in [`OnUnbalanced::on_unbalanceds`]: `fee` and
+/// then `tip`.
+#[deprecated(note = "Please use the fungible trait and FungibleAdapter instead where possible.")]
 pub struct CurrencyAdapter<C, OU>(PhantomData<(C, OU)>);
 
 /// Default implementation for a Currency and an OnUnbalanced handler.
 ///
-/// The unbalance handler is given 2 unbalanceds in [`OnUnbalanced::on_unbalanceds`]: fee and
-/// then tip.
+/// The unbalance handler is given 2 unbalanceds in [`OnUnbalanced::on_unbalanceds`]: `fee` and
+/// then `tip`.
+#[allow(deprecated)]
 impl<T, C, OU> OnChargeTransaction<T> for CurrencyAdapter<C, OU>
 where
 	T: Config,

substrate/frame/treasury/src/lib.rs

@@ -86,7 +86,7 @@ use sp_runtime::{
 	traits::{AccountIdConversion, CheckedAdd, Saturating, StaticLookup, Zero},
 	Permill, RuntimeDebug,
 };
-use sp_std::{collections::btree_map::BTreeMap, prelude::*};
+use sp_std::{collections::btree_map::BTreeMap, marker::PhantomData, prelude::*};
 
 use frame_support::{
 	dispatch::{DispatchResult, DispatchResultWithPostInfo},
@@ -1120,3 +1120,15 @@ impl<T: Config<I>, I: 'static> OnUnbalanced<NegativeImbalanceOf<T, I>> for Palle
 		Self::deposit_event(Event::Deposit { value: numeric_amount });
 	}
 }
+
+/// TypedGet implementation to get the AccountId of the Treasury.
+pub struct TreasuryAccountId<R>(PhantomData<R>);
+impl<R> sp_runtime::traits::TypedGet for TreasuryAccountId<R>
+where
+	R: crate::Config,
+{
+	type Type = <R as frame_system::Config>::AccountId;
+	fn get() -> Self::Type {
+		crate::Pallet::<R>::account_id()
+	}
+}