Inject typed request state instance

fastapi/__init__.py

@@ -21,5 +21,6 @@ from .param_functions import Security as Security
 from .requests import Request as Request
 from .responses import Response as Response
 from .routing import APIRouter as APIRouter
+from .types import TypedState as TypedState
 from .websockets import WebSocket as WebSocket
 from .websockets import WebSocketDisconnect as WebSocketDisconnect

fastapi/dependencies/models.py

@@ -29,6 +29,7 @@ class Dependant:
     background_tasks_param_name: Optional[str] = None
     security_scopes_param_name: Optional[str] = None
     security_scopes: Optional[List[str]] = None
+    state_param_name: Optional[str] = None
     use_cache: bool = True
     path: Optional[str] = None
     cache_key: Tuple[Optional[Callable[..., Any]], Tuple[str, ...]] = field(init=False)

fastapi/dependencies/utils.py

@@ -56,6 +56,7 @@ from fastapi.logger import logger
 from fastapi.security.base import SecurityBase
 from fastapi.security.oauth2 import OAuth2, SecurityScopes
 from fastapi.security.open_id_connect_url import OpenIdConnect
+from fastapi.types import RequestState, TypedState
 from fastapi.utils import create_model_field, get_path_param_names
 from pydantic import BaseModel
 from pydantic.fields import FieldInfo
@@ -335,6 +336,9 @@ def add_non_field_param_to_dependency(
     elif lenient_issubclass(type_annotation, SecurityScopes):
         dependant.security_scopes_param_name = param_name
         return True
+    elif lenient_issubclass(type_annotation, RequestState):
+        dependant.state_param_name = param_name
+        return True
     return None
 
 
@@ -360,7 +364,10 @@ def analyze_param(
         use_annotation = annotation
         type_annotation = annotation
     # Extract Annotated info
-    if get_origin(use_annotation) is Annotated:
+    origin = get_origin(annotation)
+    if origin is TypedState:
+        type_annotation = RequestState
+    if origin is Annotated:
         annotated_args = get_args(annotation)
         type_annotation = annotated_args[0]
         fastapi_annotations = [
@@ -436,6 +443,7 @@ def analyze_param(
             Response,
             StarletteBackgroundTasks,
             SecurityScopes,
+            RequestState,
         ),
     ):
         assert depends is None, f"Cannot specify `Depends` for type {type_annotation!r}"
@@ -686,6 +694,8 @@ async def solve_dependencies(
         values[dependant.security_scopes_param_name] = SecurityScopes(
             scopes=dependant.security_scopes
         )
+    if dependant.state_param_name:
+        values[dependant.state_param_name] = TypedState(_state=request.state._state)
     return SolvedDependency(
         values=values,
         errors=errors,

fastapi/types.py

@@ -1,6 +1,6 @@
 import types
 from enum import Enum
-from typing import Any, Callable, Dict, Set, Type, TypeVar, Union
+from typing import Any, Callable, Dict, Generic, Set, Type, TypeVar, Union
 
 from pydantic import BaseModel
 
@@ -8,3 +8,32 @@ DecoratedCallable = TypeVar("DecoratedCallable", bound=Callable[..., Any])
 UnionType = getattr(types, "UnionType", Union)
 ModelNameMap = Dict[Union[Type[BaseModel], Type[Enum]], str]
 IncEx = Union[Set[int], Set[str], Dict[int, Any], Dict[str, Any]]
+
+
+StateType = TypeVar("StateType", bound=Dict[str, Any])
+
+
+class RequestState:
+    pass
+
+
+class TypedState(RequestState, Generic[StateType]):
+    def __init__(self, _state: StateType) -> None:
+        super().__init__()
+        self._state = _state
+
+    def __getattr__(self, item: str) -> Any:
+        if item.startswith("_"):
+            # TODO: Restrict overriding of the _state attribute
+            return object.__getattribute__(self, item)
+        if item in self._state:
+            return self._state[item]
+        raise AttributeError(
+            f"'{self.__class__.__name__}' object has no attribute '{item}'"
+        )
+
+    def __setattr__(self, key: str, value: Any) -> None:
+        if key.startswith("_"):
+            super().__setattr__(key, value)
+        else:
+            self._state[key] = value