#2029: Passkey withdraw token fees for tx (#2040)

# Goal
The goal of this PR is to enable `pallet_transaction_pallet` to withdraw
tx fee, this is needed as our extrinsic is `unsigned`, thereby does not
gets charged by default

Closes  #2029 
Creates #2051 

# Details
- [x] Refactor some common types from `frequency-tx-payment` to
`common-primitives`
- [x] Add a withdraw fee function to be called from Validate Unsigned to
charge for tx fee
- [x] Add unit test

# Discussion
<!-- List discussion items -->

# Checklist
- [ ] Chain spec updated
- [ ] Custom RPC OR Runtime API added/changed? Updated js/api-augment.
- [ ] Design doc(s) updated
- [x] Tests added
- [ ] Benchmarks added
- [ ] Weights updated

pallets/frequency-tx-payment/src/lib.rs

@@ -418,7 +418,7 @@ where
 	) -> Result<(BalanceOf<T>, InitialPayment<T>), TransactionValidityError> {
 		let fee = pallet_transaction_payment::Pallet::<T>::compute_fee(len as u32, info, tip);
 		if fee.is_zero() {
-			return Ok((fee, InitialPayment::Free))
+			return Ok((fee, InitialPayment::Free));
 		}
 
 		<OnChargeTransactionOf<T> as OnChargeTransaction<T>>::withdraw_fee(

pallets/passkey/Cargo.toml

@@ -21,6 +21,7 @@ sp-std = { workspace = true }
 frame-benchmarking = { workspace = true, optional = true }
 sp-core = { workspace = true }
 log = { workspace = true, default-features = false }
+pallet-transaction-payment = { workspace = true }
 
 # Frequency related dependencies
 common-primitives = { default-features = false, path = "../../common/primitives" }

pallets/passkey/src/benchmarking.rs

@@ -23,6 +23,9 @@ type SignerId = app_sr25519::Public;
 
 fn generate_payload<T: Config>() -> PasskeyPayload<T> {
 	let test_account_1_pk = SignerId::generate_pair(None);
+	let test_account_1_account_id =
+		T::AccountId::decode(&mut &test_account_1_pk.encode()[..]).unwrap();
+	T::Currency::set_balance(&test_account_1_account_id.clone().into(), 1000000000u32.into());
 	let passkey_public_key = [0u8; 33];
 	let wrapped_binary = wrap_binary_data(passkey_public_key.to_vec());
 	let signature: MultiSignature =
@@ -32,7 +35,7 @@ fn generate_payload<T: Config>() -> PasskeyPayload<T> {
 		frame_system::Call::<T>::remark { remark: vec![] }.into();
 
 	let call: PasskeyCall<T> = PasskeyCall {
-		account_id: T::AccountId::decode(&mut &test_account_1_pk.encode()[..]).unwrap(),
+		account_id: test_account_1_account_id,
 		account_nonce: T::Nonce::zero(),
 		account_ownership_proof: signature,
 		call: Box::new(inner_call),
@@ -50,7 +53,7 @@ fn generate_payload<T: Config>() -> PasskeyPayload<T> {
 }
 
 benchmarks! {
-	where_clause {  where <T as frame_system::Config>::RuntimeCall: Dispatchable<Info = DispatchInfo> }
+	where_clause {  where <T as frame_system::Config>::RuntimeCall: From<Call<T>> + Dispatchable<Info = DispatchInfo, PostInfo = PostDispatchInfo> }
 
 	validate {
 		let payload = generate_payload::<T>();

pallets/passkey/src/lib.rs

@@ -16,21 +16,28 @@
 	rustdoc::invalid_codeblock_attributes,
 	missing_docs
 )]
-
 use common_primitives::utils::wrap_binary_data;
+use common_runtime::extensions::check_nonce::CheckNonce;
 use frame_support::{
 	dispatch::{DispatchInfo, GetDispatchInfo, PostDispatchInfo},
 	pallet_prelude::*,
 	traits::Contains,
 };
 use frame_system::pallet_prelude::*;
+use pallet_transaction_payment::OnChargeTransaction;
 use sp_runtime::{
-	traits::{Convert, Dispatchable, SignedExtension, Verify},
+	traits::{Convert, DispatchInfoOf, Dispatchable, SignedExtension, Verify, Zero},
+	transaction_validity::{TransactionValidity, TransactionValidityError},
 	AccountId32, MultiSignature,
 };
 use sp_std::{vec, vec::Vec};
 
-use common_runtime::extensions::check_nonce::CheckNonce;
+/// Type aliases used for interaction with `OnChargeTransaction`.
+pub(crate) type OnChargeTransactionOf<T> =
+	<T as pallet_transaction_payment::Config>::OnChargeTransaction;
+
+/// Balance type alias.
+pub(crate) type BalanceOf<T> = <OnChargeTransactionOf<T> as OnChargeTransaction<T>>::Balance;
 
 #[cfg(test)]
 mod mock;
@@ -40,6 +47,9 @@ mod tests;
 pub mod weights;
 pub use weights::*;
 
+#[cfg(feature = "runtime-benchmarks")]
+use frame_support::traits::tokens::fungible::Mutate;
+
 #[cfg(feature = "runtime-benchmarks")]
 mod benchmarking;
 
@@ -58,7 +68,7 @@ pub mod module {
 	pub const STORAGE_VERSION: StorageVersion = StorageVersion::new(0);
 
 	#[pallet::config]
-	pub trait Config: frame_system::Config {
+	pub trait Config: frame_system::Config + pallet_transaction_payment::Config {
 		/// The overarching event type.
 		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;
 
@@ -67,7 +77,8 @@ pub mod module {
 			+ Dispatchable<RuntimeOrigin = Self::RuntimeOrigin, PostInfo = PostDispatchInfo>
 			+ GetDispatchInfo
 			+ From<frame_system::Call<Self>>
-			+ IsType<<Self as frame_system::Config>::RuntimeCall>;
+			+ IsType<<Self as frame_system::Config>::RuntimeCall>
+			+ From<Call<Self>>;
 
 		/// Weight information for extrinsics in this pallet.
 		type WeightInfo: WeightInfo;
@@ -77,6 +88,10 @@ pub mod module {
 
 		/// Filters the inner calls for passkey which is set in runtime
 		type PasskeyCallFilter: Contains<<Self as Config>::RuntimeCall>;
+
+		/// Helper Curreny method for benchmarking
+		#[cfg(feature = "runtime-benchmarks")]
+		type Currency: Mutate<Self::AccountId>;
 	}
 
 	#[pallet::error]
@@ -131,28 +146,46 @@ pub mod module {
 	#[pallet::validate_unsigned]
 	impl<T: Config> ValidateUnsigned for Pallet<T>
 	where
-		<T as frame_system::Config>::RuntimeCall: Dispatchable<Info = DispatchInfo>,
+		<T as frame_system::Config>::RuntimeCall:
+			From<Call<T>> + Dispatchable<Info = DispatchInfo, PostInfo = PostDispatchInfo>,
 	{
 		type Call = Call<T>;
 		fn validate_unsigned(_source: TransactionSource, call: &Self::Call) -> TransactionValidity {
+			let valid_tx = ValidTransaction::default();
 			let payload = Self::filter_valid_calls(&call)?;
-			Self::validate_signatures(&payload)?;
-
+			let signature_validity = Self::validate_signatures(&payload)?;
 			let nonce_check = PasskeyNonce::new(payload.passkey_call.clone());
-			nonce_check.validate()
+			let nonce_validity = nonce_check.validate()?;
+			let tx_charge = ChargeTransactionPayment::<T>(
+				payload.passkey_call.account_id.clone(),
+				call.clone(),
+			);
+			let tx_payment_validity = tx_charge.validate()?;
+			let valid_tx = valid_tx
+				.combine_with(signature_validity)
+				.combine_with(nonce_validity)
+				.combine_with(tx_payment_validity);
+			Ok(valid_tx)
 		}
 
 		fn pre_dispatch(call: &Self::Call) -> Result<(), TransactionValidityError> {
-			Self::validate_unsigned(TransactionSource::InBlock, call)?;
-
 			let payload = Self::filter_valid_calls(&call)?;
+			Self::validate_signatures(&payload)?;
 			let nonce_check = PasskeyNonce::new(payload.passkey_call.clone());
-			nonce_check.pre_dispatch()
+			nonce_check.pre_dispatch()?;
+			let tx_charge = ChargeTransactionPayment::<T>(
+				payload.passkey_call.account_id.clone(),
+				call.clone(),
+			);
+			tx_charge.pre_dispatch()
 		}
 	}
 }
 
-impl<T: Config> Pallet<T> {
+impl<T: Config> Pallet<T>
+where
+	<T as frame_system::Config>::RuntimeCall: From<Call<T>> + Dispatchable<Info = DispatchInfo>,
+{
 	fn filter_valid_calls(call: &Call<T>) -> Result<PasskeyPayload<T>, TransactionValidityError> {
 		match call {
 			Call::proxy { payload }
@@ -232,3 +265,67 @@ where
 		passkey_nonce.pre_dispatch(&who, &some_call.clone().into(), info, 0usize)
 	}
 }
+
+/// Passkey related tx payment
+#[derive(Encode, Decode, Clone, TypeInfo)]
+#[scale_info(skip_type_params(T))]
+pub struct ChargeTransactionPayment<T: Config>(pub T::AccountId, pub Call<T>);
+
+impl<T: Config> ChargeTransactionPayment<T>
+where
+	<T as frame_system::Config>::RuntimeCall:
+		From<Call<T>> + Dispatchable<Info = DispatchInfo, PostInfo = PostDispatchInfo>,
+{
+	/// Validates the transaction fee paid with tokens.
+	pub fn pre_dispatch(&self) -> Result<(), TransactionValidityError> {
+		let info = &self.1.get_dispatch_info();
+		let len = self.0.using_encoded(|c| c.len());
+		let runtime_call: <T as frame_system::Config>::RuntimeCall =
+			<T as frame_system::Config>::RuntimeCall::from(self.1.clone());
+		let who = self.0.clone();
+		self.withdraw_token_fee(&who, &runtime_call, info, len, Zero::zero())?;
+		Ok(())
+	}
+
+	/// Validates the transaction fee paid with tokens.
+	pub fn validate(&self) -> TransactionValidity {
+		let info = &self.1.get_dispatch_info();
+		let len = self.0.using_encoded(|c| c.len());
+		let runtime_call: <T as frame_system::Config>::RuntimeCall =
+			<T as frame_system::Config>::RuntimeCall::from(self.1.clone());
+		let who = self.0.clone();
+		let fee = self.withdraw_token_fee(&who, &runtime_call, info, len, Zero::zero())?;
+
+		let priority = pallet_transaction_payment::ChargeTransactionPayment::<T>::get_priority(
+			info,
+			len,
+			Zero::zero(),
+			fee,
+		);
+
+		Ok(ValidTransaction { priority, ..Default::default() })
+	}
+
+	/// Withdraws transaction fee paid with tokens.
+	/// # Arguments
+	/// * `who` - The account id of the payer
+	/// * `call` - The call
+	/// # Return
+	/// * `Ok((fee, initial_payment))` if the fee is successfully withdrawn
+	/// * `Err(InvalidTransaction::Payment)` if the fee cannot be withdrawn
+	fn withdraw_token_fee(
+		&self,
+		who: &T::AccountId,
+		call: &<T as frame_system::Config>::RuntimeCall,
+		info: &DispatchInfoOf<<T as frame_system::Config>::RuntimeCall>,
+		len: usize,
+		tip: BalanceOf<T>,
+	) -> Result<BalanceOf<T>, TransactionValidityError> {
+		let fee = pallet_transaction_payment::Pallet::<T>::compute_fee(len as u32, info, tip);
+		<OnChargeTransactionOf<T> as OnChargeTransaction<T>>::withdraw_fee(
+			who, call, info, fee, tip,
+		)
+		.map(|_| (fee))
+		.map_err(|_| -> TransactionValidityError { InvalidTransaction::Payment.into() })
+	}
+}

pallets/passkey/src/mock.rs

@@ -1,26 +1,53 @@
 //! Mocks for the Passkey module.
+use crate as pallet_passkey;
+use crate::*;
 use frame_support::{
-	construct_runtime,
+	construct_runtime, parameter_types,
 	traits::{ConstU32, ConstU64, Contains, Everything},
+	weights::WeightToFee as WeightToFeeTrait,
 };
-use sp_core::H256;
+use pallet_transaction_payment::CurrencyAdapter;
+use sp_core::{ConstU8, H256};
 use sp_runtime::{
 	traits::{ConvertInto, IdentityLookup},
-	BuildStorage,
+	BuildStorage, SaturatedConversion,
 };
 
-use crate as pallet_passkey;
-
 use common_primitives::node::AccountId;
 
 type Block = frame_system::mocking::MockBlockU32<Test>;
 
+// Needs parameter_types! for the impls below
+parameter_types! {
+	pub static WeightToFee: u64 = 1;
+	pub static TransactionByteFee: u64 = 1;
+}
+
+impl WeightToFeeTrait for WeightToFee {
+	type Balance = u64;
+
+	fn weight_to_fee(weight: &Weight) -> Self::Balance {
+		Self::Balance::saturated_from(weight.ref_time())
+			.saturating_mul(WEIGHT_TO_FEE.with(|v| *v.borrow()))
+	}
+}
+
+impl WeightToFeeTrait for TransactionByteFee {
+	type Balance = u64;
+
+	fn weight_to_fee(weight: &Weight) -> Self::Balance {
+		Self::Balance::saturated_from(weight.ref_time())
+			.saturating_mul(TRANSACTION_BYTE_FEE.with(|v| *v.borrow()))
+	}
+}
+
 construct_runtime!(
 	pub enum Test
 	{
 		System: frame_system::{Pallet, Call, Storage, Config<T>, Event<T>},
 		Balances: pallet_balances::{Pallet, Call, Storage, Config<T>, Event<T>},
 		Passkey: pallet_passkey::{Pallet, Storage, Call, Event<T>, ValidateUnsigned},
+		TransactionPayment: pallet_transaction_payment::{Pallet, Storage, Event<T>},
 	}
 );
 
@@ -51,12 +78,23 @@ impl frame_system::Config for Test {
 	type MaxConsumers = ConstU32<16>;
 }
 
+impl pallet_transaction_payment::Config for Test {
+	type RuntimeEvent = RuntimeEvent;
+	type OnChargeTransaction = CurrencyAdapter<Balances, ()>;
+	type WeightToFee = WeightToFee;
+	type LengthToFee = TransactionByteFee;
+	type FeeMultiplierUpdate = ();
+	type OperationalFeeMultiplier = ConstU8<5>;
+}
+
 impl pallet_passkey::Config for Test {
 	type RuntimeEvent = RuntimeEvent;
 	type WeightInfo = ();
 	type RuntimeCall = RuntimeCall;
 	type ConvertIntoAccountId32 = ConvertInto;
 	type PasskeyCallFilter = MockPasskeyCallFilter;
+	#[cfg(feature = "runtime-benchmarks")]
+	type Currency = Balances;
 }
 
 impl pallet_balances::Config for Test {