refactor: Make command_scope optional

cq/_core/routing/di.py

@@ -2,11 +2,8 @@
 
 from abc import abstractmethod
 from collections.abc import Awaitable, Callable
-from contextlib import nullcontext
 from typing import TYPE_CHECKING, Any, Concatenate, Protocol, runtime_checkable
 
-from cq.middlewares.contextlib import AsyncContextManagerMiddleware
-
 if TYPE_CHECKING:  # pragma: no cover
     from cq import Command, CommandBus, EventBus, Middleware, QueryBus
 
@@ -23,8 +20,7 @@ class DIAdapter(Protocol):
 
     __slots__ = ()
 
-    @abstractmethod
-    def command_scope(self) -> Middleware[Concatenate[Command, ...], Any]:
+    def command_scope(self) -> Middleware[Concatenate[Command, ...], Any] | None:
         """
         Return a middleware that wraps each command dispatch.
 
@@ -39,7 +35,7 @@ def command_scope(self) -> Middleware[Concatenate[Command, ...], Any]:
         instead of writing the middleware by hand.
         """
 
-        raise NotImplementedError
+        return None
 
     @abstractmethod
     def lazy[T](self, tp: type[T]) -> Callable[[], Awaitable[T]]:
@@ -88,9 +84,6 @@ def wire[T](self, tp: type[T]) -> Callable[..., Awaitable[T]]:
 class NoDI(DIAdapter):
     __slots__ = ()
 
-    def command_scope(self) -> Middleware[Concatenate[Command, ...], Any]:
-        return AsyncContextManagerMiddleware(nullcontext())
-
     def lazy[T](self, tp: type[T], /) -> Callable[[], Awaitable[T]]:
         tp_str = getattr(tp, "__name__", str(tp))
         raise RuntimeError(

cq/_core/routing/router.py

@@ -56,7 +56,11 @@ def query_types(self) -> KeysView[type[Query]]:
 
     def new_command_bus(self) -> Bus[Command, Any]:
         bus = SimpleBus(self.__command_registry)
-        bus.add_middlewares(self.__di.command_scope())
+
+        command_scope_middleware = self.__di.command_scope()
+        if command_scope_middleware is not None:
+            bus.add_middlewares(command_scope_middleware)
+
         return bus
 
     def new_event_bus(self) -> Bus[Event, None]: