Token hook refactoring; Posthooks for deposit and transfer (#834)

* feat(tokens): Refactor hooks into single trait

* feat(tokens): Add post-hooks for Transfer and Deposit

* chore(tokens): improve mutation hook naming

Author: daniel-savu

asset-registry/src/mock/para.rs

@@ -92,16 +92,11 @@ impl orml_tokens::Config for Runtime {
 	type CurrencyId = CurrencyId;
 	type WeightInfo = ();
 	type ExistentialDeposits = ExistentialDeposits;
-	type OnDust = ();
-	type OnSlash = ();
-	type OnDeposit = ();
-	type OnTransfer = ();
+	type CurrencyHooks = ();
 	type ReserveIdentifier = [u8; 8];
 	type MaxReserves = ();
 	type MaxLocks = ConstU32<50>;
 	type DustRemovalWhitelist = Nothing;
-	type OnNewTokenAccount = ();
-	type OnKilledTokenAccount = ();
 }
 
 #[derive(scale_info::TypeInfo, Encode, Decode, Clone, Eq, PartialEq, Debug)]

currencies/src/mock.rs

@@ -8,7 +8,7 @@ use frame_support::{
 	traits::{ConstU32, ConstU64, Everything, Nothing},
 	PalletId,
 };
-use orml_traits::parameter_type_with_key;
+use orml_traits::{currency::MutationHooks, parameter_type_with_key};
 use sp_core::H256;
 use sp_runtime::{
 	testing::Header,
@@ -73,23 +73,33 @@ parameter_types! {
 	pub DustAccount: AccountId = PalletId(*b"orml/dst").into_account_truncating();
 }
 
+pub struct CurrencyHooks<T>(marker::PhantomData<T>);
+impl<T: orml_tokens::Config> MutationHooks<T::AccountId, T::CurrencyId, T::Balance> for CurrencyHooks<T>
+where
+	T::AccountId: From<AccountId32>,
+{
+	type OnDust = orml_tokens::TransferDust<T, DustAccount>;
+	type OnSlash = ();
+	type PreDeposit = ();
+	type PostDeposit = ();
+	type PreTransfer = ();
+	type PostTransfer = ();
+	type OnNewTokenAccount = ();
+	type OnKilledTokenAccount = ();
+}
+
 impl orml_tokens::Config for Runtime {
 	type RuntimeEvent = RuntimeEvent;
 	type Balance = Balance;
 	type Amount = i64;
 	type CurrencyId = CurrencyId;
 	type WeightInfo = ();
 	type ExistentialDeposits = ExistentialDeposits;
-	type OnDust = orml_tokens::TransferDust<Runtime, DustAccount>;
-	type OnSlash = ();
-	type OnDeposit = ();
-	type OnTransfer = ();
+	type CurrencyHooks = CurrencyHooks<Runtime>;
 	type MaxLocks = ConstU32<100_000>;
 	type MaxReserves = ConstU32<100_000>;
 	type ReserveIdentifier = ReserveIdentifier;
 	type DustRemovalWhitelist = Nothing;
-	type OnNewTokenAccount = ();
-	type OnKilledTokenAccount = ();
 }
 
 pub const NATIVE_CURRENCY_ID: CurrencyId = 1;

payments/src/mock.rs

@@ -98,17 +98,12 @@ impl orml_tokens::Config for Test {
 	type CurrencyId = u32;
 	type RuntimeEvent = RuntimeEvent;
 	type ExistentialDeposits = ExistentialDeposits;
-	type OnDust = ();
-	type OnSlash = ();
-	type OnDeposit = ();
-	type OnTransfer = ();
+	type CurrencyHooks = ();
 	type WeightInfo = ();
 	type MaxLocks = MaxLocks;
 	type DustRemovalWhitelist = MockDustRemovalWhitelist;
 	type MaxReserves = ConstU32<2>;
 	type ReserveIdentifier = ReserveIdentifier;
-	type OnNewTokenAccount = ();
-	type OnKilledTokenAccount = ();
 }
 
 pub struct MockDisputeResolver;

tokens/src/lib.rs

@@ -66,9 +66,9 @@ use sp_std::{cmp, convert::Infallible, marker, prelude::*, vec::Vec};
 
 use orml_traits::{
 	arithmetic::{self, Signed},
-	currency::{OnDeposit, OnSlash, OnTransfer, TransferAll},
+	currency::{MutationHooks, OnDeposit, OnDust, OnSlash, OnTransfer, TransferAll},
 	BalanceStatus, GetByKey, Happened, LockIdentifier, MultiCurrency, MultiCurrencyExtended, MultiLockableCurrency,
-	MultiReservableCurrency, NamedMultiReservableCurrency, OnDust,
+	MultiReservableCurrency, NamedMultiReservableCurrency,
 };
 
 mod imbalances;
@@ -173,7 +173,7 @@ pub use module::*;
 
 #[frame_support::pallet]
 pub mod module {
-	use orml_traits::currency::{OnDeposit, OnSlash, OnTransfer};
+	use orml_traits::currency::MutationHooks;
 
 	use super::*;
 
@@ -216,23 +216,9 @@ pub mod module {
 		/// System::AccountInfo, zero ED may cause some problems.
 		type ExistentialDeposits: GetByKey<Self::CurrencyId, Self::Balance>;
 
-		/// Handler to burn or transfer account's dust
-		type OnDust: OnDust<Self::AccountId, Self::CurrencyId, Self::Balance>;
-
-		/// Hook to run before slashing an account.
-		type OnSlash: OnSlash<Self::AccountId, Self::CurrencyId, Self::Balance>;
-
-		/// Hook to run before depositing into an account.
-		type OnDeposit: OnDeposit<Self::AccountId, Self::CurrencyId, Self::Balance>;
-
-		/// Hook to run before transferring from an account to another.
-		type OnTransfer: OnTransfer<Self::AccountId, Self::CurrencyId, Self::Balance>;
-
-		/// Handler for when an account was created
-		type OnNewTokenAccount: Happened<(Self::AccountId, Self::CurrencyId)>;
-
-		/// Handler for when an account was created
-		type OnKilledTokenAccount: Happened<(Self::AccountId, Self::CurrencyId)>;
+		/// Hooks are actions that are executed on certain events.
+		/// For example: OnDust, OnNewTokenAccount
+		type CurrencyHooks: MutationHooks<Self::AccountId, Self::CurrencyId, Self::Balance>;
 
 		#[pallet::constant]
 		type MaxLocks: Get<u32>;
@@ -765,11 +751,11 @@ impl<T: Config> Pallet<T> {
 				// Ignore the result, because if it failed then there are remaining consumers,
 				// and the account storage in frame_system shouldn't be reaped.
 				let _ = frame_system::Pallet::<T>::dec_providers(who);
-				T::OnKilledTokenAccount::happened(&(who.clone(), currency_id));
+				<T::CurrencyHooks as MutationHooks<T::AccountId, T::CurrencyId, T::Balance>>::OnKilledTokenAccount::happened(&(who.clone(), currency_id));
 			} else if !existed && exists {
 				// if new, increase account provider
 				frame_system::Pallet::<T>::inc_providers(who);
-				T::OnNewTokenAccount::happened(&(who.clone(), currency_id));
+				<T::CurrencyHooks as MutationHooks<T::AccountId, T::CurrencyId, T::Balance>>::OnNewTokenAccount::happened(&(who.clone(), currency_id));
 			}
 
 			if let Some(endowed) = maybe_endowed {
@@ -783,7 +769,7 @@ impl<T: Config> Pallet<T> {
 			if let Some(dust_amount) = maybe_dust {
 				// `OnDust` maybe get/set storage `Accounts` of `who`, trigger handler here
 				// to avoid some unexpected errors.
-				T::OnDust::on_dust(who, currency_id, dust_amount);
+				<T::CurrencyHooks as MutationHooks<T::AccountId, T::CurrencyId, T::Balance>>::OnDust::on_dust(who, currency_id, dust_amount);
 
 				Self::deposit_event(Event::DustLost {
 					currency_id,
@@ -906,7 +892,12 @@ impl<T: Config> Pallet<T> {
 			return Ok(());
 		}
 
-		T::OnTransfer::on_transfer(currency_id, from, to, amount)?;
+		<T::CurrencyHooks as MutationHooks<T::AccountId, T::CurrencyId, T::Balance>>::PreTransfer::on_transfer(
+			currency_id,
+			from,
+			to,
+			amount,
+		)?;
 		Self::try_mutate_account(to, currency_id, |to_account, _existed| -> DispatchResult {
 			Self::try_mutate_account(from, currency_id, |from_account, _existed| -> DispatchResult {
 				from_account.free = from_account
@@ -946,6 +937,12 @@ impl<T: Config> Pallet<T> {
 			Ok(())
 		})?;
 
+		<T::CurrencyHooks as MutationHooks<T::AccountId, T::CurrencyId, T::Balance>>::PostTransfer::on_transfer(
+			currency_id,
+			from,
+			to,
+			amount,
+		)?;
 		Self::deposit_event(Event::Transfer {
 			currency_id,
 			from: from.clone(),
@@ -1032,7 +1029,11 @@ impl<T: Config> Pallet<T> {
 			return Ok(());
 		}
 
-		T::OnDeposit::on_deposit(currency_id, who, amount)?;
+		<T::CurrencyHooks as MutationHooks<T::AccountId, T::CurrencyId, T::Balance>>::PreDeposit::on_deposit(
+			currency_id,
+			who,
+			amount,
+		)?;
 		Self::try_mutate_account(who, currency_id, |account, existed| -> DispatchResult {
 			if require_existed {
 				ensure!(existed, Error::<T>::DeadAccount);
@@ -1054,6 +1055,11 @@ impl<T: Config> Pallet<T> {
 			}
 			account.free = account.free.defensive_saturating_add(amount);
 
+			<T::CurrencyHooks as MutationHooks<T::AccountId, T::CurrencyId, T::Balance>>::PostDeposit::on_deposit(
+				currency_id,
+				who,
+				amount,
+			)?;
 			Self::deposit_event(Event::Deposited {
 				currency_id,
 				who: who.clone(),
@@ -1128,7 +1134,11 @@ impl<T: Config> MultiCurrency<T::AccountId> for Pallet<T> {
 			return amount;
 		}
 
-		T::OnSlash::on_slash(currency_id, who, amount);
+		<T::CurrencyHooks as MutationHooks<T::AccountId, T::CurrencyId, T::Balance>>::OnSlash::on_slash(
+			currency_id,
+			who,
+			amount,
+		);
 		let account = Self::accounts(who, currency_id);
 		let free_slashed_amount = account.free.min(amount);
 		// Cannot underflow because free_slashed_amount can never be greater than amount
@@ -1306,7 +1316,11 @@ impl<T: Config> MultiReservableCurrency<T::AccountId> for Pallet<T> {
 			return value;
 		}
 
-		T::OnSlash::on_slash(currency_id, who, value);
+		<T::CurrencyHooks as MutationHooks<T::AccountId, T::CurrencyId, T::Balance>>::OnSlash::on_slash(
+			currency_id,
+			who,
+			value,
+		);
 		let reserved_balance = Self::reserved_balance(currency_id, who);
 		let actual = reserved_balance.min(value);
 		Self::mutate_account(who, currency_id, |account, _| {