Task/trans ctx typing (#128)

* Fix return typing of AsyncEngine._trans_ctx.__aenter__
* StartableContext is made generic as to remove the assumption that it'll always be returning itself which is not the case for for it's behaviour in _trans_ctx

* tests: add testcase for #109

Co-authored-by: Faster Speeding <luke@lmbyrne.dev>

sqlalchemy-stubs/ext/asyncio/base.pyi

@@ -1,17 +1,16 @@
 import abc
 from typing import Any
 from typing import Generator
+from typing import Generic
 from typing import TypeVar
 
-_TStartableContext = TypeVar("_TStartableContext", bound=StartableContext)
+_T = TypeVar("_T")
 
-class StartableContext(abc.ABC, metaclass=abc.ABCMeta):
+class StartableContext(abc.ABC, Generic[_T], metaclass=abc.ABCMeta):
     @abc.abstractmethod
-    async def start(self: _TStartableContext) -> _TStartableContext: ...
-    def __await__(
-        self: _TStartableContext,
-    ) -> Generator[Any, None, _TStartableContext]: ...
-    async def __aenter__(self: _TStartableContext) -> _TStartableContext: ...
+    async def start(self) -> _T: ...
+    def __await__(self) -> Generator[Any, None, _T]: ...
+    async def __aenter__(self) -> _T: ...
     @abc.abstractmethod
     async def __aexit__(
         self, type_: Any, value: Any, traceback: Any

sqlalchemy-stubs/ext/asyncio/engine.pyi

@@ -22,7 +22,9 @@ def create_async_engine(*arg: Any, **kw: Any) -> AsyncEngine: ...
 
 class AsyncConnectable: ...
 
-class AsyncConnection(ProxyComparable, StartableContext, AsyncConnectable):
+class AsyncConnection(
+    ProxyComparable, StartableContext["AsyncConnection"], AsyncConnectable
+):
     # copied from future.Connection via create_proxy_methods
     @property
     def closed(self) -> bool: ...
@@ -102,12 +104,12 @@ class AsyncEngine(ProxyComparable, AsyncConnectable):
     def update_execution_options(self, **opt: Any) -> None: ...
     def get_execution_options(self) -> Mapping[Any, Any]: ...
     # end copied
-    class _trans_ctx(StartableContext):
+    class _trans_ctx(StartableContext[AsyncConnection]):
         conn: AsyncConnection = ...
         def __init__(self, conn: AsyncConnection) -> None: ...
         transaction: Any = ...
-        async def start(self) -> AsyncConnection: ...  # type: ignore[override]
-        def __await__(self) -> Generator[Any, None, AsyncConnection]: ...  # type: ignore[override]
+        async def start(self) -> AsyncConnection: ...
+        def __await__(self) -> Generator[Any, None, AsyncConnection]: ...
         async def __aexit__(
             self, type_: Any, value: Any, traceback: Any
         ) -> None: ...
@@ -119,7 +121,7 @@ class AsyncEngine(ProxyComparable, AsyncConnectable):
     def execution_options(self, **opt: Any) -> AsyncEngine: ...
     async def dispose(self) -> None: ...
 
-class AsyncTransaction(ProxyComparable, StartableContext):
+class AsyncTransaction(ProxyComparable, StartableContext["AsyncTransaction"]):
     connection: AsyncConnection = ...
     sync_transaction: Optional[Transaction] = ...
     nested: bool = ...

sqlalchemy-stubs/ext/asyncio/session.pyi

@@ -151,7 +151,7 @@ class _AsyncSessionContextManager:
         self, type_: Any, value: Any, traceback: Any
     ) -> None: ...
 
-class AsyncSessionTransaction(StartableContext):
+class AsyncSessionTransaction(StartableContext["AsyncSessionTransaction"]):
     session: AsyncSession = ...
     nested: bool = ...
     sync_transaction: Optional[Any] = ...

test/files/async_context_processor_ticket_109.py

@@ -0,0 +1,11 @@
+from sqlalchemy import literal
+from sqlalchemy import select
+from sqlalchemy.ext import asyncio
+
+
+async def test() -> None:
+    database = asyncio.create_async_engine("", future=True)
+
+    trans_ctx = database.begin()
+    async with trans_ctx as connection:
+        await connection.execute(select(literal(1)))