feat(runtime): Adding dust and slash handlers (#3405)

gsdk/src/metadata/generated.rs

@@ -3280,8 +3280,8 @@ pub mod runtime_types {
                 #[doc = "\n\t\t\tThe [event](https://docs.substrate.io/main-docs/build/events-errors/) emitted\n\t\t\tby this pallet.\n\t\t\t"]
                 pub enum Event {
                     #[codec(index = 0)]
-                    #[doc = "Transferred to the pool from an external account."]
-                    Refilled { amount: ::core::primitive::u128 },
+                    #[doc = "Deposited to the pool."]
+                    Deposited { amount: ::core::primitive::u128 },
                     #[codec(index = 1)]
                     #[doc = "Transferred from the pool to an external account."]
                     Withdrawn { amount: ::core::primitive::u128 },

pallets/staking-rewards/src/lib.rs

@@ -231,8 +231,8 @@ pub mod pallet {
     #[pallet::event]
     #[pallet::generate_deposit(pub(super) fn deposit_event)]
     pub enum Event<T: Config> {
-        /// Transferred to the pool from an external account.
-        Refilled { amount: BalanceOf<T> },
+        /// Deposited to the pool.
+        Deposited { amount: BalanceOf<T> },
         /// Transferred from the pool to an external account.
         Withdrawn { amount: BalanceOf<T> },
         /// Burned from the pool.
@@ -271,7 +271,7 @@ pub mod pallet {
                 log::error!("Failed to replenish the staking rewards pool: {:?}", e);
                 Error::<T>::FailureToRefillPool
             })?;
-            Self::deposit_event(Event::Refilled { amount: value });
+            Self::deposit_event(Event::Deposited { amount: value });
 
             Ok(())
         }
@@ -295,7 +295,7 @@ pub mod pallet {
                 log::error!("Failed to replenish the staking rewards pool: {:?}", e);
                 Error::<T>::FailureToRefillPool
             })?;
-            Self::deposit_event(Event::Refilled { amount: value });
+            Self::deposit_event(Event::Deposited { amount: value });
 
             Ok(())
         }
@@ -403,6 +403,8 @@ impl<T: Config> EraPayout<BalanceOf<T>> for Pallet<T> {
     }
 }
 
+/// Balance out excessive total supply whenever new tokens are minted through
+/// burning the equivalent amount from the inflation offset pool
 impl<T: Config> OnUnbalanced<PositiveImbalanceOf<T>> for Pallet<T> {
     fn on_nonzero_unbalanced(minted: PositiveImbalanceOf<T>) {
         let amount = minted.peek();
@@ -420,22 +422,38 @@ impl<T: Config> OnUnbalanced<PositiveImbalanceOf<T>> for Pallet<T> {
             Self::deposit_event(Event::Burned { amount });
         } else {
             log::warn!(
-                "Staking rewards pool has insufficient balance to burn minted rewards. The currency total supply may grow."
+                "Staking rewards pool has insufficient balance to burn minted rewards. \
+                The currency total supply may grow."
             );
         };
     }
 }
 
+/// Funnel the funds-to-burn into the inflation offset pool to maintain the total supply
+pub struct OffsetPool<T>(sp_std::marker::PhantomData<T>);
+impl<T: Config> OnUnbalanced<NegativeImbalanceOf<T>> for OffsetPool<T> {
+    fn on_nonzero_unbalanced(amount: NegativeImbalanceOf<T>) {
+        let numeric_amount = amount.peek();
+
+        // Should resolve into existing but resolving with creation is a safer bet anyway
+        T::Currency::resolve_creating(&Pallet::<T>::account_id(), amount);
+
+        Pallet::deposit_event(Event::<T>::Deposited {
+            amount: numeric_amount,
+        });
+    }
+}
+
 /// A type to be plugged into the Staking pallet as the `RewardRemainder` associated type.
 ///
-/// Implements the `OnUnbalanced<NegativeImbalance>` trait in a way that would try to burn
-/// the amount equivalent to that provided in the input `NegativeImbalance` from the rewards
-/// pool in order to keep the token total supply intact. It is assumed that the subsequent
-/// `OnUnbalanced` handler (e.g. Treasury) would `resolve` the imbalance and not drop it -
-/// otherwise the the total supply will decrease.
-pub struct RewardsStash<T, U>(sp_std::marker::PhantomData<(T, U)>);
-
-impl<T: Config, U> OnUnbalanced<NegativeImbalanceOf<T>> for RewardsStash<T, U>
+/// A wrapper around the final `RewardRemainder` destination that burns from the inflation offset
+/// pool the equivalent of the provided `NegativeImbalance` value in order to balance out what has
+/// been minted as a part of the staking rewards for the era but not yet attributed to any account.
+/// It is assumed that the subsequent `OnUnbalanced` handler (e.g. Treasury) would `resolve` the
+/// imbalance and not drop it - otherwise the the total supply will decrease.
+pub struct RewardProxy<T, U>(sp_std::marker::PhantomData<(T, U)>);
+
+impl<T: Config, U> OnUnbalanced<NegativeImbalanceOf<T>> for RewardProxy<T, U>
 where
     U: OnUnbalanced<NegativeImbalanceOf<T>>,
 {