pep484 ORM / SQL result support

after some experimentation it seems mypy is more amenable
to the generic types being fully integrated rather than
having separate spin-off types.   so key structures
like Result, Row, Select become generic.  For DML
Insert, Update, Delete, these are spun into type-specific
subclasses ReturningInsert, ReturningUpdate, ReturningDelete,
which is fine since the "row-ness" of these constructs
doesn't happen until returning() is called in any case.

a Tuple based model is then integrated so that these
objects can carry along information about their return
types.  Overloads at the .execute() level carry through
the Tuple from the invoked object to the result.

To suit the issue of AliasedClass generating attributes
that are dynamic, experimented with a custom subclass
AsAliased, but then just settled on having aliased()
lie to the type checker and return `Type[_O]`, essentially.
will need some type-related accessors for with_polymorphic()
also.

Additionally, identified an issue in Update when used
"mysql style" against a join(), it basically doesn't work
if asked to UPDATE two tables on the same column name.
added an error message to the specific condition where
it happens with a very non-specific error message that we
hit a thing we can't do right now, suggest multi-table
update as a possible cause.

Change-Id: I5eff7eefe1d6166ee74160b2785c5e6a81fa8b95

1 files changed, 131 insertions, 4 deletions

diff --git a/lib/sqlalchemy/ext/asyncio/scoping.py b/lib/sqlalchemy/ext/asyncio/scoping.py
index c7a6e2ca0..22a060a0d 100644
--- a/lib/sqlalchemy/ext/asyncio/scoping.py
+++ b/lib/sqlalchemy/ext/asyncio/scoping.py
@@ -12,10 +12,12 @@ from typing import Callable
 from typing import Iterable
 from typing import Iterator
 from typing import Optional
+from typing import overload
 from typing import Sequence
 from typing import Tuple
 from typing import Type
 from typing import TYPE_CHECKING
+from typing import TypeVar
 from typing import Union
 
 from .session import async_sessionmaker
@@ -37,9 +39,9 @@ if TYPE_CHECKING:
     from ...engine import Engine
     from ...engine import Result
     from ...engine import Row
+    from ...engine import RowMapping
     from ...engine.interfaces import _CoreAnyExecuteParams
     from ...engine.interfaces import _CoreSingleExecuteParams
-    from ...engine.interfaces import _ExecuteOptions
     from ...engine.interfaces import _ExecuteOptionsParameter
     from ...engine.result import ScalarResult
     from ...orm._typing import _IdentityKeyType
@@ -52,6 +54,9 @@ if TYPE_CHECKING:
     from ...sql.base import Executable
     from ...sql.elements import ClauseElement
     from ...sql.selectable import ForUpdateArg
+    from ...sql.selectable import TypedReturnsRows
+
+_T = TypeVar("_T", bound=Any)
 
 
 @create_proxy_methods(
@@ -480,6 +485,32 @@ class async_scoped_session:
 
         return await self._proxied.delete(instance)
 
+    @overload
+    async def execute(
+        self,
+        statement: TypedReturnsRows[_T],
+        params: Optional[_CoreAnyExecuteParams] = None,
+        *,
+        execution_options: _ExecuteOptionsParameter = util.EMPTY_DICT,
+        bind_arguments: Optional[_BindArguments] = None,
+        _parent_execute_state: Optional[Any] = None,
+        _add_event: Optional[Any] = None,
+    ) -> Result[_T]:
+        ...
+
+    @overload
+    async def execute(
+        self,
+        statement: Executable,
+        params: Optional[_CoreAnyExecuteParams] = None,
+        *,
+        execution_options: _ExecuteOptionsParameter = util.EMPTY_DICT,
+        bind_arguments: Optional[_BindArguments] = None,
+        _parent_execute_state: Optional[Any] = None,
+        _add_event: Optional[Any] = None,
+    ) -> Result[Any]:
+        ...
+
     async def execute(
         self,
         statement: Executable,
@@ -488,7 +519,7 @@ class async_scoped_session:
         execution_options: _ExecuteOptionsParameter = util.EMPTY_DICT,
         bind_arguments: Optional[_BindArguments] = None,
         **kw: Any,
-    ) -> Result:
+    ) -> Result[Any]:
         r"""Execute a statement and return a buffered
         :class:`_engine.Result` object.
 
@@ -916,6 +947,30 @@ class async_scoped_session:
 
         return await self._proxied.rollback()
 
+    @overload
+    async def scalar(
+        self,
+        statement: TypedReturnsRows[Tuple[_T]],
+        params: Optional[_CoreSingleExecuteParams] = None,
+        *,
+        execution_options: _ExecuteOptionsParameter = util.EMPTY_DICT,
+        bind_arguments: Optional[_BindArguments] = None,
+        **kw: Any,
+    ) -> Optional[_T]:
+        ...
+
+    @overload
+    async def scalar(
+        self,
+        statement: Executable,
+        params: Optional[_CoreSingleExecuteParams] = None,
+        *,
+        execution_options: _ExecuteOptionsParameter = util.EMPTY_DICT,
+        bind_arguments: Optional[_BindArguments] = None,
+        **kw: Any,
+    ) -> Any:
+        ...
+
     async def scalar(
         self,
         statement: Executable,
@@ -947,6 +1002,30 @@ class async_scoped_session:
             **kw,
         )
 
+    @overload
+    async def scalars(
+        self,
+        statement: TypedReturnsRows[Tuple[_T]],
+        params: Optional[_CoreSingleExecuteParams] = None,
+        *,
+        execution_options: _ExecuteOptionsParameter = util.EMPTY_DICT,
+        bind_arguments: Optional[_BindArguments] = None,
+        **kw: Any,
+    ) -> ScalarResult[_T]:
+        ...
+
+    @overload
+    async def scalars(
+        self,
+        statement: Executable,
+        params: Optional[_CoreSingleExecuteParams] = None,
+        *,
+        execution_options: _ExecuteOptionsParameter = util.EMPTY_DICT,
+        bind_arguments: Optional[_BindArguments] = None,
+        **kw: Any,
+    ) -> ScalarResult[Any]:
+        ...
+
     async def scalars(
         self,
         statement: Executable,
@@ -984,6 +1063,19 @@ class async_scoped_session:
             **kw,
         )
 
+    @overload
+    async def stream(
+        self,
+        statement: TypedReturnsRows[_T],
+        params: Optional[_CoreAnyExecuteParams] = None,
+        *,
+        execution_options: _ExecuteOptionsParameter = util.EMPTY_DICT,
+        bind_arguments: Optional[_BindArguments] = None,
+        **kw: Any,
+    ) -> AsyncResult[_T]:
+        ...
+
+    @overload
     async def stream(
         self,
         statement: Executable,
@@ -992,7 +1084,18 @@ class async_scoped_session:
         execution_options: _ExecuteOptionsParameter = util.EMPTY_DICT,
         bind_arguments: Optional[_BindArguments] = None,
         **kw: Any,
-    ) -> AsyncResult:
+    ) -> AsyncResult[Any]:
+        ...
+
+    async def stream(
+        self,
+        statement: Executable,
+        params: Optional[_CoreAnyExecuteParams] = None,
+        *,
+        execution_options: _ExecuteOptionsParameter = util.EMPTY_DICT,
+        bind_arguments: Optional[_BindArguments] = None,
+        **kw: Any,
+    ) -> AsyncResult[Any]:
         r"""Execute a statement and return a streaming
         :class:`_asyncio.AsyncResult` object.
 
@@ -1012,6 +1115,30 @@ class async_scoped_session:
             **kw,
         )
 
+    @overload
+    async def stream_scalars(
+        self,
+        statement: TypedReturnsRows[Tuple[_T]],
+        params: Optional[_CoreSingleExecuteParams] = None,
+        *,
+        execution_options: _ExecuteOptionsParameter = util.EMPTY_DICT,
+        bind_arguments: Optional[_BindArguments] = None,
+        **kw: Any,
+    ) -> AsyncScalarResult[_T]:
+        ...
+
+    @overload
+    async def stream_scalars(
+        self,
+        statement: Executable,
+        params: Optional[_CoreSingleExecuteParams] = None,
+        *,
+        execution_options: _ExecuteOptionsParameter = util.EMPTY_DICT,
+        bind_arguments: Optional[_BindArguments] = None,
+        **kw: Any,
+    ) -> AsyncScalarResult[Any]:
+        ...
+
     async def stream_scalars(
         self,
         statement: Executable,
@@ -1323,7 +1450,7 @@ class async_scoped_session:
         ident: Union[Any, Tuple[Any, ...]] = None,
         *,
         instance: Optional[Any] = None,
-        row: Optional[Row] = None,
+        row: Optional[Union[Row[Any], RowMapping]] = None,
         identity_token: Optional[Any] = None,
     ) -> _IdentityKeyType[Any]:
         r"""Return an identity key.