Ensure no error is possible in apply_validated_transaction and fix …

…`correct_and_deposit_fee` (#497)

* Ensure no error is possible in `apply_validated_transaction`

* Fix lints

* Fix correct_and_deposit_fee should not be able to error

* Change ensure to assert

* Fix tests

frame/ethereum/src/lib.rs

@@ -210,9 +210,7 @@ pub mod pallet {
 					Self::validate_transaction_in_block(source, &transaction).expect(
 						"pre-block transaction verification failed; the block cannot be built",
 					);
-					Self::apply_validated_transaction(source, transaction).expect(
-						"pre-block transaction execution failed; the block cannot be built",
-					);
+					Self::apply_validated_transaction(source, transaction);
 				}
 			}
 
@@ -233,12 +231,12 @@ pub mod pallet {
 		) -> DispatchResultWithPostInfo {
 			let source = ensure_ethereum_transaction(origin)?;
 			// Disable transact functionality if PreLog exist.
-			ensure!(
+			assert!(
 				fp_consensus::find_pre_log(&frame_system::Pallet::<T>::digest()).is_err(),
-				Error::<T>::PreLogExists,
+				"pre log already exists; block is invalid",
 			);
 
-			Self::apply_validated_transaction(source, transaction)
+			Ok(Self::apply_validated_transaction(source, transaction))
 		}
 	}
 
@@ -457,10 +455,7 @@ impl<T: Config> Pallet<T> {
 		builder.build()
 	}
 
-	fn apply_validated_transaction(
-		source: H160,
-		transaction: Transaction,
-	) -> DispatchResultWithPostInfo {
+	fn apply_validated_transaction(source: H160, transaction: Transaction) -> PostDispatchInfo {
 		let transaction_hash =
 			H256::from_slice(Keccak256::digest(&rlp::encode(&transaction)).as_slice());
 		let transaction_index = Pending::<T>::get().len() as u32;
@@ -474,7 +469,8 @@ impl<T: Config> Pallet<T> {
 			Some(transaction.nonce),
 			transaction.action,
 			None,
-		)?;
+		)
+		.expect("transaction is already validated; error indicates that the block is invalid");
 
 		let (reason, status, used_gas, dest) = match info {
 			CallOrCreateInfo::Call(info) => (
@@ -535,13 +531,13 @@ impl<T: Config> Pallet<T> {
 			transaction_hash,
 			reason,
 		));
-		Ok(PostDispatchInfo {
+
+		PostDispatchInfo {
 			actual_weight: Some(T::GasWeightMapping::gas_to_weight(
 				used_gas.unique_saturated_into(),
 			)),
 			pays_fee: Pays::No,
-		})
-		.into()
+		}
 	}
 
 	/// Get the transaction status with given index.

frame/ethereum/src/tests.rs

@@ -26,9 +26,9 @@ use frame_support::{
 	unsigned::{TransactionValidityError, ValidateUnsigned},
 };
 use rustc_hex::{FromHex, ToHex};
-use sp_runtime::traits::Applyable;
-use sp_runtime::transaction_validity::{
-	InvalidTransaction, TransactionSource, ValidTransactionBuilder,
+use sp_runtime::{
+	traits::Applyable,
+	transaction_validity::{InvalidTransaction, TransactionSource, ValidTransactionBuilder},
 };
 use std::str::FromStr;
 

frame/evm/src/lib.rs

@@ -655,7 +655,7 @@ pub trait OnChargeEVMTransaction<T: Config> {
 		who: &H160,
 		corrected_fee: U256,
 		already_withdrawn: Self::LiquidityInfo,
-	) -> Result<(), Error<T>>;
+	);
 }
 
 /// Implements the transaction payment for a pallet implementing the `Currency`
@@ -697,7 +697,7 @@ where
 		who: &H160,
 		corrected_fee: U256,
 		already_withdrawn: Self::LiquidityInfo,
-	) -> Result<(), Error<T>> {
+	) {
 		if let Some(paid) = already_withdrawn {
 			let account_id = T::AddressMapping::into_account_id(*who);
 
@@ -714,10 +714,9 @@ where
 			let adjusted_paid = paid
 				.offset(refund_imbalance)
 				.same()
-				.map_err(|_| Error::<T>::BalanceLow)?;
+				.unwrap_or_else(|_| C::NegativeImbalance::zero());
 			OU::on_unbalanced(adjusted_paid);
 		}
-		Ok(())
 	}
 }
 
@@ -743,7 +742,7 @@ impl<T> OnChargeEVMTransaction<T> for ()
 		who: &H160,
 		corrected_fee: U256,
 		already_withdrawn: Self::LiquidityInfo,
-	) -> Result<(), Error<T>> {
-		EVMCurrencyAdapter::<<T as Config>::Currency, ()>::correct_and_deposit_fee(who, corrected_fee, already_withdrawn)
+	) {
+		<EVMCurrencyAdapter::<<T as Config>::Currency, ()> as OnChargeEVMTransaction<T>>::correct_and_deposit_fee(who, corrected_fee, already_withdrawn)
 	}
 }

frame/evm/src/runner/stack.rs

@@ -114,7 +114,7 @@ impl<T: Config> Runner<T> {
 		);
 
 		// Refund fees to the `source` account if deducted more before,
-		T::OnChargeTransaction::correct_and_deposit_fee(&source, actual_fee, fee)?;
+		T::OnChargeTransaction::correct_and_deposit_fee(&source, actual_fee, fee);
 
 		let state = executor.into_state();
 

frame/evm/src/tests.rs

@@ -108,7 +108,7 @@ fn fee_deduction() {
 		assert_eq!(Balances::free_balance(&substrate_addr), 90);
 
 		// Refund fees as 5 units
-		<<Test as Config>::OnChargeTransaction as OnChargeEVMTransaction<Test>>::correct_and_deposit_fee(&evm_addr, U256::from(5), imbalance).unwrap();
+		<<Test as Config>::OnChargeTransaction as OnChargeEVMTransaction<Test>>::correct_and_deposit_fee(&evm_addr, U256::from(5), imbalance);
 		assert_eq!(Balances::free_balance(&substrate_addr), 95);
 	});
 }