Adding try_state hook for Treasury pallet

substrate/frame/treasury/src/lib.rs

@@ -83,13 +83,16 @@ use codec::{Decode, Encode, MaxEncodedLen};
 use scale_info::TypeInfo;
 
 use sp_runtime::{
-	traits::{AccountIdConversion, CheckedAdd, Saturating, StaticLookup, Zero},
+	traits::{
+		AccountIdConversion, CheckedAdd, SaturatedConversion, Saturating, StaticLookup, Zero,
+	},
 	Permill, RuntimeDebug,
 };
 use sp_std::{collections::btree_map::BTreeMap, prelude::*};
 
 use frame_support::{
-	print,
+	dispatch::{DispatchResult, DispatchResultWithPostInfo},
+	ensure, print,
 	traits::{
 		tokens::Pay, Currency, ExistenceRequirement::KeepAlive, Get, Imbalance, OnUnbalanced,
 		ReservableCurrency, WithdrawReasons,
@@ -456,6 +459,12 @@ pub mod pallet {
 				Weight::zero()
 			}
 		}
+
+		#[cfg(feature = "try-runtime")]
+		fn try_state(_: T::BlockNumber) -> Result<(), sp_runtime::TryRuntimeError> {
+			Self::do_try_state()?;
+			Ok(())
+		}
 	}
 
 	#[derive(Default)]
@@ -855,7 +864,7 @@ pub mod pallet {
 				// spend has expired and no further status update is expected.
 				Spends::<T, I>::remove(index);
 				Self::deposit_event(Event::<T, I>::SpendProcessed { index });
-				return Ok(Pays::No.into())
+				return Ok(Pays::No.into());
 			}
 
 			let payment_id = match spend.status {
@@ -872,11 +881,11 @@ pub mod pallet {
 				Status::Success | Status::Unknown => {
 					Spends::<T, I>::remove(index);
 					Self::deposit_event(Event::<T, I>::SpendProcessed { index });
-					return Ok(Pays::No.into())
+					return Ok(Pays::No.into());
 				},
 				Status::InProgress => return Err(Error::<T, I>::Inconclusive.into()),
 			}
-			return Ok(Pays::Yes.into())
+			return Ok(Pays::Yes.into());
 		}
 
 		/// Void previously approved spend.
@@ -1020,6 +1029,72 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 			// Must never be less than 0 but better be safe.
 			.saturating_sub(T::Currency::minimum_balance())
 	}
+
+	/// Ensure the correctness of the state of this pallet.
+	///
+	/// ## Invariants
+	///
+	/// 1. [`ProposalCount`] >= [`Proposals`].count(). The [`ProposalCount`] SV is only increased, but never
+	///    decreased whereas individual proposals can be removed from the [`Proposals`] SM.
+	/// 2. [`T::ProposalBondMinimum`] * Number of proposals with non-zero bond <= sum_{p in Proposals} p.bond.
+	/// 3. (Optional) [`T::ProposalBondMaximum`] * Number of proposals with non-zero bond >= sum_{p in Proposals} p.bond.
+	/// 4. Each [`ProposalIndex`] contained in [`Approvals`] should exist in [`Proposals`]. Note, that this
+	///    automatically implies Approvals.count() <= Proposals.count().
+	/// 5. [`SpendCount`] >= [`Spends`].count(). Follows the same reasoning as (1).
+	/// 6. For each spend entry contained in `Spends` we should have spend.expire_at > spend.valid_from.
+	#[cfg(any(feature = "try-runtime", test))]
+	fn do_try_state() -> Result<(), sp_runtime::TryRuntimeError> {
+		ensure!(
+			ProposalCount::<T, I>::get() as usize >= Proposals::<T, I>::iter().count(),
+			"Actual number of proposals exceeds `ProposalCount`."
+		);
+
+		let (total_amount_bonded, non_zero_count) = Proposals::<T, I>::iter().fold(
+			(BalanceOf::<T, I>::zero(), 0usize),
+			|(sum, count), (_index, proposal)| {
+				if proposal.bond != BalanceOf::<T, I>::zero() {
+					(sum + proposal.bond, count + 1)
+				} else {
+					(sum, count)
+				}
+			},
+		);
+		ensure!(
+			T::ProposalBondMinimum::get() * non_zero_count.saturated_into() <= total_amount_bonded,
+			"Total amount bonded falls short of required minimum."
+		);
+		if let Some(proposal_bond_maximum) = T::ProposalBondMaximum::get() {
+			ensure!(
+				proposal_bond_maximum * non_zero_count.saturated_into() >= total_amount_bonded,
+				"Total amount bonded exceeds required maximum."
+			);
+		}
+
+		Approvals::<T, I>::get()
+			.iter()
+			.try_for_each(|proposal_index| -> DispatchResult {
+				ensure!(
+					Proposals::<T, I>::contains_key(proposal_index),
+					"Proposal indices in `Approvals` must also be contained in `Proposals`."
+				);
+				Ok(())
+			})?;
+
+		ensure!(
+			SpendCount::<T, I>::get() as usize >= Spends::<T, I>::iter().count(),
+			"Number of spends exceeds `SpendCount`."
+		);
+
+		Spends::<T, I>::iter().try_for_each(|(_index, spend)| -> DispatchResult {
+			ensure!(
+				spend.valid_from < spend.expire_at,
+				"Spend cannot expire before it becomes valid."
+			);
+			Ok(())
+		})?;
+
+		Ok(())
+	}
 }
 
 impl<T: Config<I>, I: 'static> OnUnbalanced<NegativeImbalanceOf<T, I>> for Pallet<T, I> {