Fix the type-hints using more standard mode (#526)

Author: ischaojie

databases/backends/aiopg.py

@@ -104,7 +104,7 @@ class AiopgConnection(ConnectionBackend):
     def __init__(self, database: AiopgBackend, dialect: Dialect):
         self._database = database
         self._dialect = dialect
-        self._connection = None  # type: typing.Optional[aiopg.Connection]
+        self._connection: typing.Optional[aiopg.Connection] = None
 
     async def acquire(self) -> None:
         assert self._connection is None, "Connection is already acquired"

databases/backends/asyncmy.py

@@ -92,7 +92,7 @@ class AsyncMyConnection(ConnectionBackend):
     def __init__(self, database: AsyncMyBackend, dialect: Dialect):
         self._database = database
         self._dialect = dialect
-        self._connection = None  # type: typing.Optional[asyncmy.Connection]
+        self._connection: typing.Optional[asyncmy.Connection] = None
 
     async def acquire(self) -> None:
         assert self._connection is None, "Connection is already acquired"

databases/backends/mysql.py

@@ -92,7 +92,7 @@ class MySQLConnection(ConnectionBackend):
     def __init__(self, database: MySQLBackend, dialect: Dialect):
         self._database = database
         self._dialect = dialect
-        self._connection = None  # type: typing.Optional[aiomysql.Connection]
+        self._connection: typing.Optional[aiomysql.Connection] = None
 
     async def acquire(self) -> None:
         assert self._connection is None, "Connection is already acquired"

databases/backends/postgres.py

@@ -45,7 +45,7 @@ def _get_dialect(self) -> Dialect:
     def _get_connection_kwargs(self) -> dict:
         url_options = self._database_url.options
 
-        kwargs = {}  # type: typing.Dict[str, typing.Any]
+        kwargs: typing.Dict[str, typing.Any] = {}
         min_size = url_options.get("min_size")
         max_size = url_options.get("max_size")
         ssl = url_options.get("ssl")
@@ -162,7 +162,7 @@ class PostgresConnection(ConnectionBackend):
     def __init__(self, database: PostgresBackend, dialect: Dialect):
         self._database = database
         self._dialect = dialect
-        self._connection = None  # type: typing.Optional[asyncpg.connection.Connection]
+        self._connection: typing.Optional[asyncpg.connection.Connection] = None
 
     async def acquire(self) -> None:
         assert self._connection is None, "Connection is already acquired"
@@ -305,9 +305,7 @@ def raw_connection(self) -> asyncpg.connection.Connection:
 class PostgresTransaction(TransactionBackend):
     def __init__(self, connection: PostgresConnection):
         self._connection = connection
-        self._transaction = (
-            None
-        )  # type: typing.Optional[asyncpg.transaction.Transaction]
+        self._transaction: typing.Optional[asyncpg.transaction.Transaction] = None
 
     async def start(
         self, is_root: bool, extra_options: typing.Dict[typing.Any, typing.Any]

databases/backends/sqlite.py

@@ -80,7 +80,7 @@ class SQLiteConnection(ConnectionBackend):
     def __init__(self, pool: SQLitePool, dialect: Dialect):
         self._pool = pool
         self._dialect = dialect
-        self._connection = None  # type: typing.Optional[aiosqlite.Connection]
+        self._connection: typing.Optional[aiosqlite.Connection] = None
 
     async def acquire(self) -> None:
         assert self._connection is None, "Connection is already acquired"

databases/core.py

@@ -64,12 +64,12 @@ def __init__(
         self._backend = backend_cls(self.url, **self.options)
 
         # Connections are stored as task-local state.
-        self._connection_context = ContextVar("connection_context")  # type: ContextVar
+        self._connection_context: ContextVar = ContextVar("connection_context")
 
         # When `force_rollback=True` is used, we use a single global
         # connection, within a transaction that always rolls back.
-        self._global_connection = None  # type: typing.Optional[Connection]
-        self._global_transaction = None  # type: typing.Optional[Transaction]
+        self._global_connection: typing.Optional[Connection] = None
+        self._global_transaction: typing.Optional[Transaction] = None
 
     async def connect(self) -> None:
         """
@@ -223,7 +223,7 @@ def __init__(self, backend: DatabaseBackend) -> None:
         self._connection_counter = 0
 
         self._transaction_lock = asyncio.Lock()
-        self._transaction_stack = []  # type: typing.List[Transaction]
+        self._transaction_stack: typing.List[Transaction] = []
 
         self._query_lock = asyncio.Lock()