Bridge: slash destination may be an explicit account (#4106)

Extracted to a separate PR as requested here:
paritytech/parity-bridges-common#2873 (comment)

bridges/bin/runtime-common/src/extensions/refund_relayer_extension.rs

@@ -23,7 +23,7 @@ use crate::messages_call_ext::{
 	CallHelper as MessagesCallHelper, CallInfo as MessagesCallInfo, MessagesCallSubType,
 };
 use bp_messages::{LaneId, MessageNonce};
-use bp_relayers::{RewardsAccountOwner, RewardsAccountParams};
+use bp_relayers::{ExplicitOrAccountParams, RewardsAccountOwner, RewardsAccountParams};
 use bp_runtime::{Chain, Parachain, ParachainIdOf, RangeInclusiveExt, StaticStrProvider};
 use codec::{Codec, Decode, Encode};
 use frame_support::{
@@ -589,7 +589,10 @@ where
 				);
 			},
 			RelayerAccountAction::Slash(relayer, slash_account) =>
-				RelayersPallet::<T::Runtime>::slash_and_deregister(&relayer, slash_account),
+				RelayersPallet::<T::Runtime>::slash_and_deregister(
+					&relayer,
+					ExplicitOrAccountParams::Params(slash_account),
+				),
 		}
 
 		Ok(())

bridges/modules/relayers/src/benchmarking.rs

@@ -106,7 +106,7 @@ benchmarks! {
 		let slash_destination = RewardsAccountParams::new(lane, *b"test", RewardsAccountOwner::ThisChain);
 		T::prepare_rewards_account(slash_destination, Zero::zero());
 	}: {
-		crate::Pallet::<T>::slash_and_deregister(&relayer, slash_destination)
+		crate::Pallet::<T>::slash_and_deregister(&relayer, slash_destination.into())
 	}
 	verify {
 		assert!(!crate::Pallet::<T>::is_registration_active(&relayer));

bridges/modules/relayers/src/lib.rs

@@ -21,7 +21,8 @@
 #![warn(missing_docs)]
 
 use bp_relayers::{
-	PaymentProcedure, Registration, RelayerRewardsKeyProvider, RewardsAccountParams, StakeAndSlash,
+	ExplicitOrAccountParams, PaymentProcedure, Registration, RelayerRewardsKeyProvider,
+	RewardsAccountParams, StakeAndSlash,
 };
 use bp_runtime::StorageDoubleMapKeyProvider;
 use frame_support::fail;
@@ -242,7 +243,7 @@ pub mod pallet {
 		/// It may fail inside, but error is swallowed and we only log it.
 		pub fn slash_and_deregister(
 			relayer: &T::AccountId,
-			slash_destination: RewardsAccountParams,
+			slash_destination: ExplicitOrAccountParams<T::AccountId>,
 		) {
 			let registration = match RegisteredRelayers::<T>::take(relayer) {
 				Some(registration) => registration,
@@ -259,7 +260,7 @@ pub mod pallet {
 
 			match T::StakeAndSlash::repatriate_reserved(
 				relayer,
-				slash_destination,
+				slash_destination.clone(),
 				registration.stake,
 			) {
 				Ok(failed_to_slash) if failed_to_slash.is_zero() => {

bridges/modules/relayers/src/stake_adapter.rs

@@ -17,7 +17,7 @@
 //! Code that allows `NamedReservableCurrency` to be used as a `StakeAndSlash`
 //! mechanism of the relayers pallet.
 
-use bp_relayers::{PayRewardFromAccount, RewardsAccountParams, StakeAndSlash};
+use bp_relayers::{ExplicitOrAccountParams, PayRewardFromAccount, StakeAndSlash};
 use codec::Codec;
 use frame_support::traits::{tokens::BalanceStatus, NamedReservableCurrency};
 use sp_runtime::{traits::Get, DispatchError, DispatchResult};
@@ -55,11 +55,14 @@ where
 
 	fn repatriate_reserved(
 		relayer: &AccountId,
-		beneficiary: RewardsAccountParams,
+		beneficiary: ExplicitOrAccountParams<AccountId>,
 		amount: Currency::Balance,
 	) -> Result<Currency::Balance, DispatchError> {
-		let beneficiary_account =
-			PayRewardFromAccount::<(), AccountId>::rewards_account(beneficiary);
+		let beneficiary_account = match beneficiary {
+			ExplicitOrAccountParams::Explicit(account) => account,
+			ExplicitOrAccountParams::Params(params) =>
+				PayRewardFromAccount::<(), AccountId>::rewards_account(params),
+		};
 		Currency::repatriate_reserved_named(
 			&ReserveId::get(),
 			relayer,
@@ -134,7 +137,11 @@ mod tests {
 			Balances::mint_into(&beneficiary_account, expected_balance).unwrap();
 
 			assert_eq!(
-				TestStakeAndSlash::repatriate_reserved(&1, beneficiary, test_stake()),
+				TestStakeAndSlash::repatriate_reserved(
+					&1,
+					ExplicitOrAccountParams::Params(beneficiary),
+					test_stake()
+				),
 				Ok(test_stake())
 			);
 			assert_eq!(Balances::free_balance(1), 0);
@@ -146,7 +153,11 @@ mod tests {
 			Balances::mint_into(&2, test_stake() * 2).unwrap();
 			TestStakeAndSlash::reserve(&2, test_stake() / 3).unwrap();
 			assert_eq!(
-				TestStakeAndSlash::repatriate_reserved(&2, beneficiary, test_stake()),
+				TestStakeAndSlash::repatriate_reserved(
+					&2,
+					ExplicitOrAccountParams::Params(beneficiary),
+					test_stake()
+				),
 				Ok(test_stake() - test_stake() / 3)
 			);
 			assert_eq!(Balances::free_balance(2), test_stake() * 2 - test_stake() / 3);
@@ -158,7 +169,11 @@ mod tests {
 			Balances::mint_into(&3, test_stake() * 2).unwrap();
 			TestStakeAndSlash::reserve(&3, test_stake()).unwrap();
 			assert_eq!(
-				TestStakeAndSlash::repatriate_reserved(&3, beneficiary, test_stake()),
+				TestStakeAndSlash::repatriate_reserved(
+					&3,
+					ExplicitOrAccountParams::Params(beneficiary),
+					test_stake()
+				),
 				Ok(0)
 			);
 			assert_eq!(Balances::free_balance(3), test_stake());
@@ -176,7 +191,12 @@ mod tests {
 
 			Balances::mint_into(&3, test_stake() * 2).unwrap();
 			TestStakeAndSlash::reserve(&3, test_stake()).unwrap();
-			assert!(TestStakeAndSlash::repatriate_reserved(&3, beneficiary, test_stake()).is_err());
+			assert!(TestStakeAndSlash::repatriate_reserved(
+				&3,
+				ExplicitOrAccountParams::Params(beneficiary),
+				test_stake()
+			)
+			.is_err());
 			assert_eq!(Balances::free_balance(3), test_stake());
 			assert_eq!(Balances::reserved_balance(3), test_stake());
 			assert_eq!(Balances::free_balance(beneficiary_account), 0);

bridges/primitives/relayers/src/lib.rs

@@ -19,7 +19,7 @@
 #![warn(missing_docs)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
-pub use registration::{Registration, StakeAndSlash};
+pub use registration::{ExplicitOrAccountParams, Registration, StakeAndSlash};
 
 use bp_messages::LaneId;
 use bp_runtime::{ChainId, StorageDoubleMapKeyProvider};

bridges/primitives/relayers/src/registration.rs

@@ -46,6 +46,21 @@ use sp_runtime::{
 	DispatchError, DispatchResult,
 };
 
+/// Either explicit account reference or `RewardsAccountParams`.
+#[derive(Clone, Debug)]
+pub enum ExplicitOrAccountParams<AccountId> {
+	/// Explicit account reference.
+	Explicit(AccountId),
+	/// Account, referenced using `RewardsAccountParams`.
+	Params(RewardsAccountParams),
+}
+
+impl<AccountId> From<RewardsAccountParams> for ExplicitOrAccountParams<AccountId> {
+	fn from(params: RewardsAccountParams) -> Self {
+		ExplicitOrAccountParams::Params(params)
+	}
+}
+
 /// Relayer registration.
 #[derive(Copy, Clone, Debug, Decode, Encode, Eq, PartialEq, TypeInfo, MaxEncodedLen)]
 pub struct Registration<BlockNumber, Balance> {
@@ -90,7 +105,7 @@ pub trait StakeAndSlash<AccountId, BlockNumber, Balance> {
 	/// Returns `Ok(_)` with non-zero balance if we have failed to repatriate some portion of stake.
 	fn repatriate_reserved(
 		relayer: &AccountId,
-		beneficiary: RewardsAccountParams,
+		beneficiary: ExplicitOrAccountParams<AccountId>,
 		amount: Balance,
 	) -> Result<Balance, DispatchError>;
 }
@@ -113,7 +128,7 @@ where
 
 	fn repatriate_reserved(
 		_relayer: &AccountId,
-		_beneficiary: RewardsAccountParams,
+		_beneficiary: ExplicitOrAccountParams<AccountId>,
 		_amount: Balance,
 	) -> Result<Balance, DispatchError> {
 		Ok(Zero::zero())