Handle system refcounts for pallet-evm managed contracts (paritytech#288)

Author: sorpaas

frame/evm/src/backend.rs

@@ -141,93 +141,3 @@ impl<'vicinity, T: Trait> BackendT for Backend<'vicinity, T> {
 		AccountStorages::get(address, index)
 	}
 }
-
-impl<'vicinity, T: Trait> ApplyBackend for Backend<'vicinity, T> {
-	fn apply<A, I, L>(
-		&mut self,
-		values: A,
-		logs: L,
-		delete_empty: bool,
-	) where
-		A: IntoIterator<Item=Apply<I>>,
-		I: IntoIterator<Item=(H256, H256)>,
-		L: IntoIterator<Item=evm::backend::Log>,
-	{
-		for apply in values {
-			match apply {
-				Apply::Modify {
-					address, basic, code, storage, reset_storage,
-				} => {
-					Module::<T>::mutate_account_basic(&address, Account {
-						nonce: basic.nonce,
-						balance: basic.balance,
-					});
-
-					if let Some(code) = code {
-						debug::debug!(
-							target: "evm",
-							"Inserting code ({} bytes) at {:?}",
-							code.len(),
-							address
-						);
-						AccountCodes::insert(address, code);
-					}
-
-					if reset_storage {
-						AccountStorages::remove_prefix(address);
-					}
-
-					for (index, value) in storage {
-						if value == H256::default() {
-							debug::debug!(
-								target: "evm",
-								"Removing storage for {:?} [index: {:?}]",
-								address,
-								index
-							);
-							AccountStorages::remove(address, index);
-						} else {
-							debug::debug!(
-								target: "evm",
-								"Updating storage for {:?} [index: {:?}, value: {:?}]",
-								address,
-								index,
-								value
-							);
-							AccountStorages::insert(address, index, value);
-						}
-					}
-
-					if delete_empty {
-						Module::<T>::remove_account_if_empty(&address);
-					}
-				},
-				Apply::Delete { address } => {
-					debug::debug!(
-						target: "evm",
-						"Deleting account at {:?}",
-						address
-					);
-					Module::<T>::remove_account(&address)
-				},
-			}
-		}
-
-		for log in logs {
-			debug::trace!(
-				target: "evm",
-				"Inserting log for {:?}, topics ({}) {:?}, data ({}): {:?}]",
-				log.address,
-				log.topics.len(),
-				log.topics,
-				log.data.len(),
-				log.data
-			);
-			Module::<T>::deposit_event(Event::<T>::Log(Log {
-				address: log.address,
-				topics: log.topics,
-				data: log.data,
-			}));
-		}
-	}
-}

frame/evm/src/lib.rs

@@ -522,10 +522,29 @@ impl<T: Config> Module<T> {
 
 	/// Remove an account.
 	pub fn remove_account(address: &H160) {
+		if AccountCodes::contains_key(address) {
+			let account_id = T::AddressMapping::into_account_id(*address);
+			frame_system::Module::<T>::dec_ref(&account_id);
+		}
+
 		AccountCodes::remove(address);
 		AccountStorages::remove_prefix(address);
 	}
 
+	/// Create an account.
+	pub fn create_account(address: H160, code: Vec<u8>) {
+		if code.is_empty() {
+			return
+		}
+
+		if !AccountCodes::contains_key(&address) {
+			let account_id = T::AddressMapping::into_account_id(address);
+			frame_system::Module::<T>::inc_ref(&account_id);
+		}
+
+		AccountCodes::insert(address, code);
+	}
+
 	/// Get the account basic in EVM format.
 	pub fn account_basic(address: &H160) -> Account {
 		let account_id = T::AddressMapping::into_account_id(*address);

frame/evm/src/runner/stack.rs

@@ -483,7 +483,7 @@ impl<'vicinity, 'config, T: Config> StackStateT<'config> for SubstrateStackState
 			code.len(),
 			address
 		);
-		AccountCodes::insert(address, code);
+		Module::<T>::create_account(address, code);
 	}
 
 	fn transfer(&mut self, transfer: Transfer) -> Result<(), ExitError> {