Remove async_generator and async_exit_stack deps, as starlette uses c…

…ontextlib2

docs/en/docs/tutorial/dependencies/dependencies-with-yield.md

@@ -7,15 +7,6 @@ To do this, use `yield` instead of `return`, and write the extra steps after.
 !!! tip
     Make sure to use `yield` one single time.
 
-!!! info
-    For this to work, you need to use **Python 3.7** or above, or in **Python 3.6**, install the "backports":
-
-    ```
-    pip install async-exit-stack async-generator
-    ```
-
-    This installs <a href="https://github.com/sorcio/async_exit_stack" class="external-link" target="_blank">async-exit-stack</a> and <a href="https://github.com/python-trio/async_generator" class="external-link" target="_blank">async-generator</a>.
-
 !!! note "Technical Details"
     Any function that is valid to use with:
 

docs/en/docs/tutorial/sql-databases.md

@@ -441,17 +441,6 @@ You can find an example of Alembic in a FastAPI project in the templates from [P
 
 ### Create a dependency
 
-!!! info
-    For this to work, you need to use **Python 3.7** or above, or in **Python 3.6**, install the "backports":
-
-    ```console
-    $ pip install async-exit-stack async-generator
-    ```
-
-    This installs <a href="https://github.com/sorcio/async_exit_stack" class="external-link" target="_blank">async-exit-stack</a> and <a href="https://github.com/python-trio/async_generator" class="external-link" target="_blank">async-generator</a>.
-
-    You can also use the alternative method with a "middleware" explained at the end.
-
 Now use the `SessionLocal` class we created in the `sql_app/databases.py` file to create a dependency.
 
 We need to have an independent database session/connection (`SessionLocal`) per request, use the same session through all the request and then close it after the request is finished.

fastapi/concurrency.py

@@ -1,46 +1,34 @@
-from typing import Any, Callable
-
-from starlette.concurrency import iterate_in_threadpool as iterate_in_threadpool  # noqa
-from starlette.concurrency import run_in_threadpool as run_in_threadpool  # noqa
-from starlette.concurrency import (  # noqa
-    run_until_first_complete as run_until_first_complete,
+import sys
+from typing import AsyncGenerator, ContextManager, TypeVar
+
+__all__ = [
+    "iterate_in_threadpool",
+    "run_in_threadpool",
+    "run_until_first_complete",
+    "contextmanager_in_threadpool",
+    "asynccontextmanager",
+    "AsyncExitStack",
+]
+
+from starlette.concurrency import (
+    iterate_in_threadpool,
+    run_in_threadpool,
+    run_until_first_complete,
 )
 
-asynccontextmanager_error_message = """
-FastAPI's contextmanager_in_threadpool require Python 3.7 or above,
-or the backport for Python 3.6, installed with:
-    pip install async-generator
-"""
-
-
-def _fake_asynccontextmanager(func: Callable[..., Any]) -> Callable[..., Any]:
-    def raiser(*args: Any, **kwargs: Any) -> Any:
-        raise RuntimeError(asynccontextmanager_error_message)
-
-    return raiser
+if sys.version_info >= (3, 7):
+    from contextlib import AsyncExitStack, asynccontextmanager
+else:
+    from contextlib2 import AsyncExitStack, asynccontextmanager
 
 
-try:
-    from contextlib import asynccontextmanager as asynccontextmanager  # type: ignore
-except ImportError:
-    try:
-        from async_generator import (  # type: ignore  # isort: skip
-            asynccontextmanager as asynccontextmanager,
-        )
-    except ImportError:  # pragma: no cover
-        asynccontextmanager = _fake_asynccontextmanager
-
-try:
-    from contextlib import AsyncExitStack as AsyncExitStack  # type: ignore
-except ImportError:
-    try:
-        from async_exit_stack import AsyncExitStack as AsyncExitStack  # type: ignore
-    except ImportError:  # pragma: no cover
-        AsyncExitStack = None  # type: ignore
+_T = TypeVar("_T")
 
 
-@asynccontextmanager  # type: ignore
-async def contextmanager_in_threadpool(cm: Any) -> Any:
+@asynccontextmanager
+async def contextmanager_in_threadpool(
+    cm: ContextManager[_T],
+) -> AsyncGenerator[_T, None]:
     try:
         yield await run_in_threadpool(cm.__enter__)
     except Exception as e:

fastapi/dependencies/utils.py

@@ -20,7 +20,6 @@
 from fastapi import params
 from fastapi.concurrency import (
     AsyncExitStack,
-    _fake_asynccontextmanager,
     asynccontextmanager,
     contextmanager_in_threadpool,
 )
@@ -266,18 +265,6 @@ def get_typed_annotation(param: inspect.Parameter, globalns: Dict[str, Any]) ->
     return annotation
 
 
-async_contextmanager_dependencies_error = """
-FastAPI dependencies with yield require Python 3.7 or above,
-or the backports for Python 3.6, installed with:
-    pip install async-exit-stack async-generator
-"""
-
-
-def check_dependency_contextmanagers() -> None:
-    if AsyncExitStack is None or asynccontextmanager == _fake_asynccontextmanager:
-        raise RuntimeError(async_contextmanager_dependencies_error)  # pragma: no cover
-
-
 def get_dependant(
     *,
     path: str,
@@ -289,8 +276,6 @@ def get_dependant(
     path_param_names = get_path_param_names(path)
     endpoint_signature = get_typed_signature(call)
     signature_params = endpoint_signature.parameters
-    if is_gen_callable(call) or is_async_gen_callable(call):
-        check_dependency_contextmanagers()
     dependant = Dependant(call=call, name=name, path=path, use_cache=use_cache)
     for param_name, param in signature_params.items():
         if isinstance(param.default, params.Depends):
@@ -452,14 +437,6 @@ async def solve_generator(
     if is_gen_callable(call):
         cm = contextmanager_in_threadpool(contextmanager(call)(**sub_values))
     elif is_async_gen_callable(call):
-        if not inspect.isasyncgenfunction(call):
-            # asynccontextmanager from the async_generator backfill pre python3.7
-            # does not support callables that are not functions or methods.
-            # See https://github.com/python-trio/async_generator/issues/32
-            #
-            # Expand the callable class into its __call__ method before decorating it.
-            # This approach will work on newer python versions as well.
-            call = getattr(call, "__call__", None)
         cm = asynccontextmanager(call)(**sub_values)
     return await stack.enter_async_context(cm)
 
@@ -539,10 +516,7 @@ async def solve_dependencies(
             solved = dependency_cache[sub_dependant.cache_key]
         elif is_gen_callable(call) or is_async_gen_callable(call):
             stack = request.scope.get("fastapi_astack")
-            if stack is None:
-                raise RuntimeError(
-                    async_contextmanager_dependencies_error
-                )  # pragma: no cover
+            assert isinstance(stack, AsyncExitStack)
             solved = await solve_generator(
                 call=call, stack=stack, sub_values=sub_values
             )

pyproject.toml

@@ -58,8 +58,6 @@ test = [
     "databases[sqlite] >=0.3.2,<0.4.0",
     "orjson >=3.2.1,<4.0.0",
     "ujson >=4.0.1,<5.0.0",
-    "async_exit_stack >=1.0.1,<2.0.0",
-    "async_generator >=1.10,<2.0.0",
     "python-multipart >=0.0.5,<0.0.6",
     "flask >=1.1.2,<2.0.0"
 ]
@@ -90,8 +88,6 @@ all = [
     "orjson >=3.2.1,<4.0.0",
     "email_validator >=1.1.1,<2.0.0",
     "uvicorn[standard] >=0.12.0,<0.14.0",
-    "async_exit_stack >=1.0.1,<2.0.0",
-    "async_generator >=1.10,<2.0.0"
 ]
 
 [tool.isort]