Use MaxEncodedLen + test

Author: librelois

pallets/parachain-staking/src/types.rs

@@ -22,7 +22,7 @@ use crate::{
 	Total,
 };
 use frame_support::pallet_prelude::*;
-use parity_scale_codec::{Decode, Encode};
+use parity_scale_codec::{Decode, Encode, MaxEncodedLen};
 use sp_runtime::{
 	traits::{Saturating, Zero},
 	Perbill, Percent, RuntimeDebug,
@@ -34,7 +34,8 @@ pub struct CountedDelegations<T: Config> {
 	pub rewardable_delegations: Vec<Bond<T::AccountId, BalanceOf<T>>>,
 }
 
-#[derive(Clone, Encode, Decode, RuntimeDebug, TypeInfo)]
+#[derive(Clone, Encode, Decode, RuntimeDebug, TypeInfo, MaxEncodedLen)]
+#[codec(mel_bound(AccountId: MaxEncodedLen, Balance: MaxEncodedLen))]
 pub struct Bond<AccountId, Balance> {
 	pub owner: AccountId,
 	pub amount: Balance,
@@ -1101,7 +1102,7 @@ pub enum DelegatorAdded<B> {
 }
 
 #[allow(deprecated)]
-#[derive(Clone, PartialEq, Encode, Decode, RuntimeDebug, TypeInfo)]
+#[derive(Clone, PartialEq, Encode, Decode, RuntimeDebug, TypeInfo, MaxEncodedLen)]
 pub enum DelegatorStatus {
 	/// Active with no scheduled exit
 	Active,

precompiles/parachain-staking/src/lib.rs

@@ -30,6 +30,7 @@ use frame_support::sp_runtime::Percent;
 use frame_support::traits::{fungible::Inspect, Get};
 use pallet_evm::AddressMapping;
 use pallet_parachain_staking::ScheduledRequest;
+use parity_scale_codec::{Compact, Encode};
 use precompile_utils::prelude::*;
 use sp_core::{H160, U256};
 use sp_runtime::traits::Dispatchable;
@@ -52,10 +53,10 @@ pub struct ParachainStakingPrecompile<Runtime>(PhantomData<Runtime>);
 impl<Runtime> ParachainStakingPrecompile<Runtime>
 where
 	Runtime: pallet_parachain_staking::Config + pallet_evm::Config,
-	Runtime::AccountId: Into<H160>,
+	Runtime::AccountId: Into<H160> + MaxEncodedLen,
 	Runtime::RuntimeCall: Dispatchable<PostInfo = PostDispatchInfo> + GetDispatchInfo,
 	Runtime::RuntimeCall: From<pallet_parachain_staking::Call<Runtime>>,
-	BalanceOf<Runtime>: TryFrom<U256> + Into<U256> + solidity::Codec,
+	BalanceOf<Runtime>: TryFrom<U256> + Into<U256> + solidity::Codec + MaxEncodedLen,
 	<Runtime as pallet_evm::Config>::AddressMapping: AddressMapping<Runtime::AccountId>,
 {
 	// Constants
@@ -979,4 +980,29 @@ where
 			.try_into()
 			.map_err(|_| RevertReason::value_is_too_large("balance type").into())
 	}
+
+	/// Proof-size upper bound for one read of [`pallet_parachain_staking::Pallet::delegator_state`]
+	/// storage (`Twox64Concat` + `AccountId` key, max-sized SCALE `Delegator` value).
+	pub(crate) fn delegator_state_storage_read_proof_size() -> usize {
+		/// [`frame_support::Twox64Concat`] output length (bytes); Substrate storage key prefix.
+		const TWOX64_CONCAT_PREFIX_LEN: usize = 8;
+		let max_d =
+			<Runtime as pallet_parachain_staking::Config>::MaxDelegationsPerDelegator::get();
+		let delegation_compact_prefix = Compact(max_d).encode().len();
+		let max_bonds_bytes = (max_d as usize).saturating_mul(pallet_parachain_staking::Bond::<
+			Runtime::AccountId,
+			BalanceOf<Runtime>,
+		>::max_encoded_len());
+		// Delegator Max Size = AccountId + MaxDelegationsCompact + (max_d * BondSize) + Balance + Balance + DelegatorStatus
+		let value_max = Runtime::AccountId::max_encoded_len()
+			.saturating_add(delegation_compact_prefix)
+			.saturating_add(max_bonds_bytes)
+			.saturating_add(BalanceOf::<Runtime>::max_encoded_len())
+			.saturating_add(BalanceOf::<Runtime>::max_encoded_len())
+			.saturating_add(pallet_parachain_staking::DelegatorStatus::max_encoded_len());
+		// Total = TWOX64_CONCAT_PREFIX_LEN + AccountId + value_max
+		TWOX64_CONCAT_PREFIX_LEN
+			.saturating_add(Runtime::AccountId::max_encoded_len())
+			.saturating_add(value_max)
+	}
 }

precompiles/parachain-staking/src/tests.rs

@@ -15,15 +15,20 @@
 // along with Moonbeam.  If not, see <http://www.gnu.org/licenses/>.
 
 use crate::mock::{
-	events, roll_to, roll_to_round_begin, set_points, ExtBuilder, PCall, ParachainStaking,
-	Precompiles, PrecompilesValue, Runtime, RuntimeCall, RuntimeOrigin,
+	events, roll_to, roll_to_round_begin, set_points, AccountId, ExtBuilder, PCall,
+	ParachainStaking, Precompiles, PrecompilesValue, Runtime, RuntimeCall, RuntimeOrigin,
 };
+use crate::ParachainStakingPrecompile;
 use core::str::from_utf8;
 use fp_evm::MAX_TRANSACTION_GAS_LIMIT;
 use frame_support::assert_ok;
+use frame_support::pallet_prelude::MaxEncodedLen;
 use frame_support::sp_runtime::Percent;
+use frame_support::traits::fungible::Inspect;
 use pallet_evm::Call as EvmCall;
 use pallet_parachain_staking::Event as StakingEvent;
+use pallet_parachain_staking::{Bond, Config as StakingConfig, DelegatorStatus};
+use parity_scale_codec::{Compact, Encode};
 use precompile_utils::{prelude::*, testing::*};
 use sp_core::{H160, U256};
 use sp_runtime::traits::Dispatchable;
@@ -1746,3 +1751,26 @@ fn test_deprecated_solidity_selectors_are_supported() {
 		}
 	}
 }
+
+/// Mirrors the proof-size composition in [`ParachainStakingPrecompile::delegator_state_storage_read_proof_size`]
+/// so this test fails if the helper drifts from the SCALE upper-bound model.
+#[test]
+fn delegator_state_storage_read_proof_size_matches_scale_upper_bound() {
+	type Bal =
+		<<Runtime as pallet_parachain_staking::Config>::Currency as Inspect<AccountId>>::Balance;
+
+	const TWOX64_CONCAT_PREFIX_LEN: usize = 8;
+	let max_d = <Runtime as StakingConfig>::MaxDelegationsPerDelegator::get();
+	let expected = TWOX64_CONCAT_PREFIX_LEN
+		.saturating_add(AccountId::max_encoded_len())
+		.saturating_add(AccountId::max_encoded_len())
+		.saturating_add(Compact(max_d).encode().len())
+		.saturating_add((max_d as usize).saturating_mul(Bond::<AccountId, Bal>::max_encoded_len()))
+		.saturating_add(Bal::max_encoded_len())
+		.saturating_add(Bal::max_encoded_len())
+		.saturating_add(DelegatorStatus::max_encoded_len());
+
+	let charged = ParachainStakingPrecompile::<Runtime>::delegator_state_storage_read_proof_size();
+
+	assert_eq!(charged, expected);
+}