feat: allow before_request and after_request handlers to accept a parent argument, to wrap or override the handler from an enclosing scope

Author: charles-dyfis-net

litestar/handlers/http_handlers/base.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import functools
+import inspect
 from enum import Enum
 from typing import TYPE_CHECKING, AnyStr, Mapping, Sequence, TypedDict, cast
 
@@ -62,6 +64,15 @@
 __all__ = ("HTTPRouteHandler", "route")
 
 
+def _wrap_layered_hooks(hooks: list[AsyncAnyCallable]) -> AsyncAnyCallable | None:
+    """Given a list of callables, starting from the end, set the parent= keyword argument of each to default to the preceding hook should any preceding hook exist and should that argument be accepted."""
+    if not hooks:
+        return None
+    if "parent" in inspect.signature(hooks[-1]).parameters:
+        return functools.partial(hooks[-1], parent=_wrap_layered_hooks(hooks[:-1]))
+    return hooks[-1]
+
+
 class ResponseHandlerMap(TypedDict):
     default_handler: Callable[[Any], Awaitable[ASGIApp]] | EmptyType
     response_type_handler: Callable[[Any], Awaitable[ASGIApp]] | EmptyType
@@ -260,9 +271,9 @@ def __init__(
         )
 
         self.after_request = ensure_async_callable(after_request) if after_request else None  # pyright: ignore
-        self.after_response = ensure_async_callable(after_response) if after_response else None
+        self.after_response = ensure_async_callable(after_response) if after_response else None  # pyright: ignore
         self.background = background
-        self.before_request = ensure_async_callable(before_request) if before_request else None
+        self.before_request = ensure_async_callable(before_request) if before_request else None  # pyright: ignore
         self.cache = cache
         self.cache_control = cache_control
         self.cache_key_builder = cache_key_builder
@@ -400,7 +411,7 @@ def resolve_before_request(self) -> AsyncAnyCallable | None:
         """
         if self._resolved_before_request is Empty:
             before_request_handlers = [layer.before_request for layer in self.ownership_layers if layer.before_request]
-            self._resolved_before_request = before_request_handlers[-1] if before_request_handlers else None
+            self._resolved_before_request = _wrap_layered_hooks(before_request_handlers)
         return cast("AsyncAnyCallable | None", self._resolved_before_request)
 
     def resolve_after_response(self) -> AsyncAnyCallable | None:
@@ -418,7 +429,7 @@ def resolve_after_response(self) -> AsyncAnyCallable | None:
                 for layer in self.ownership_layers
                 if layer.after_response
             ]
-            self._resolved_after_response = after_response_handlers[-1] if after_response_handlers else None
+            self._resolved_after_response = _wrap_layered_hooks(after_response_handlers)
 
         return cast("AsyncAnyCallable | None", self._resolved_after_response)
 

litestar/handlers/http_handlers/decorators.py

@@ -121,8 +121,9 @@ def __init__(
                 :class:`BackgroundTasks <.background_tasks.BackgroundTasks>` to execute after the response is finished.
                 Defaults to ``None``.
             before_request: A sync or async function called immediately before calling the route handler. Receives
-                the :class:`.connection.Request` instance and any non-``None`` return value is used for the response,
-                bypassing the route handler.
+                the :class:`.connection.Request` instance (and, if it accepts a keyword argument named `parent`, the
+                outer scope's before_request handler if any exists). Any non-``None`` return value is used for the
+                response, bypassing the route handler.
             cache: Enables response caching if configured on the application level. Valid values are ``True`` or a number
                 of seconds (e.g. ``120``) to cache the response.
             cache_control: A ``cache-control`` header of type

litestar/router.py

@@ -168,8 +168,8 @@ def __init__(
         """
 
         self.after_request = ensure_async_callable(after_request) if after_request else None  # pyright: ignore
-        self.after_response = ensure_async_callable(after_response) if after_response else None
-        self.before_request = ensure_async_callable(before_request) if before_request else None
+        self.after_response = ensure_async_callable(after_response) if after_response else None  # pyright: ignore
+        self.before_request = ensure_async_callable(before_request) if before_request else None  # pyright: ignore
         self.cache_control = cache_control
         self.dto = dto
         self.etag = etag

litestar/types/callable_types.py

@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from typing import TYPE_CHECKING, Any, AsyncGenerator, Awaitable, Callable, Generator, TypeVar
+from typing import TYPE_CHECKING, Any, AsyncGenerator, Awaitable, Callable, Generator, Protocol, TypeVar
 
 if TYPE_CHECKING:
     from typing_extensions import TypeAlias
@@ -23,12 +23,29 @@
 AfterRequestHookHandler: TypeAlias = (
     "Callable[[ASGIApp], SyncOrAsyncUnion[ASGIApp]] | Callable[[Response], SyncOrAsyncUnion[Response]]"
 )
-AfterResponseHookHandler: TypeAlias = "Callable[[Request], SyncOrAsyncUnion[None]]"
+
+AfterResponseHookHandlerSimple: TypeAlias = "Callable[[Request], SyncOrAsyncUnion[None]]"
+
+
+class AfterResponseHookHandlerWithParent(Protocol):
+    async def __call__(self, request: Request, /, *, parent: AfterResponseHookHandler | None = None) -> None: ...
+
+
+AfterResponseHookHandler: TypeAlias = "AfterResponseHookHandlerSimple | AfterResponseHookHandlerWithParent"
+
 AsyncAnyCallable: TypeAlias = Callable[..., Awaitable[Any]]
 AnyCallable: TypeAlias = Callable[..., Any]
 AnyGenerator: TypeAlias = "Generator[Any, Any, Any] | AsyncGenerator[Any, Any]"
 BeforeMessageSendHookHandler: TypeAlias = "Callable[[Message, Scope], SyncOrAsyncUnion[None]]"
-BeforeRequestHookHandler: TypeAlias = "Callable[[Request], Any | Awaitable[Any]]"
+
+
+class BeforeRequestHookHandlerWithParent(Protocol):
+    async def __call__(self, request: Request, /, *, parent: BeforeRequestHookHandler | None = None) -> Any: ...
+
+
+BeforeRequestHookHandlerSimple: TypeAlias = "Callable[[Request], Any | Awaitable[Any]]"
+BeforeRequestHookHandler: TypeAlias = "BeforeRequestHookHandlerSimple | BeforeRequestHookHandlerWithParent"
+
 CacheKeyBuilder: TypeAlias = "Callable[[Request], str]"
 ExceptionHandler: TypeAlias = "Callable[[Request, ExceptionT], Response]"
 ExceptionLoggingHandler: TypeAlias = "Callable[[Logger, Scope, list[str]], None]"

tests/e2e/test_life_cycle_hooks/test_before_request.py

@@ -1,4 +1,5 @@
-from typing import Any, Dict, Optional
+import logging
+from typing import Any, Dict, Optional, Union
 
 import pytest
 
@@ -7,6 +8,18 @@
 from litestar.testing import create_test_client
 from litestar.types import AnyCallable, BeforeRequestHookHandler
 
+logger = logging.getLogger(__name__)
+
+
+async def async_before_request_handler_with_parent(
+    request: Request[Any, Any, State], /, *, parent: Optional[BeforeRequestHookHandler] = None
+) -> Optional[Dict[str, Union[str, int]]]:
+    assert isinstance(request, Request)
+    retval: Dict[str, Union[str, int]] = (None if parent is None else await parent(request)) or {}
+    retval.setdefault("amended_count", 0)
+    retval["amended_count"] += 1  # type: ignore
+    return retval
+
 
 def sync_before_request_handler_with_return_value(request: Request[Any, Any, State]) -> Dict[str, str]:
     assert isinstance(request, Request)
@@ -88,6 +101,27 @@ def handler() -> Dict[str, str]:
             {"hello": "world"},
         ],
         [None, None, None, async_before_request_handler_without_return_value, {"hello": "world"}],
+        [
+            sync_before_request_handler_with_return_value,
+            None,
+            None,
+            async_before_request_handler_with_parent,
+            {"hello": "moon", "amended_count": 1},
+        ],
+        [
+            sync_before_request_handler_with_return_value,
+            None,
+            async_before_request_handler_with_parent,
+            async_before_request_handler_with_parent,
+            {"hello": "moon", "amended_count": 2},
+        ],
+        [
+            sync_before_request_handler_with_return_value,
+            async_before_request_handler_with_parent,
+            async_before_request_handler_with_parent,
+            async_before_request_handler_with_parent,
+            {"hello": "moon", "amended_count": 3},
+        ],
     ],
 )
 def test_before_request_handler_resolution(