feat: validate async endpoints

dmr/validation/controller.py

@@ -1,3 +1,4 @@
+import inspect
 import types
 from typing import TYPE_CHECKING
 
@@ -19,12 +20,30 @@ def __call__(
         controller: type['Controller[BaseSerializer]'],
     ) -> bool | None:
         """Run the validation."""
+        self._validate_async_generator_endpoints(controller)
         is_async = self._validate_endpoints_color(controller)
         self._validate_error_handlers(controller, is_async=is_async)
         self._validate_meta_mixins(controller)
         self._validate_non_endpoints(controller)
         return is_async
 
+    def _validate_async_generator_endpoints(
+        self,
+        controller: type['Controller[BaseSerializer]'],
+    ) -> None:
+        for method_name in controller.allowed_http_methods:
+            method = getattr(controller, method_name, None)
+            if isinstance(
+                method,
+                types.FunctionType,
+            ) and inspect.isasyncgenfunction(method):
+                raise EndpointMetadataError(
+                    f'{controller!r}.{method_name} is an async generator. '
+                    'HTTP endpoints cannot use `yield` in method body. '
+                    'Return an iterator object instead, '
+                    'for example: `return self._events()`',
+                )
+
     def _validate_endpoints_color(
         self,
         controller: type['Controller[BaseSerializer]'],

tests/test_unit/test_controllers/test_controller_validation.py

@@ -1,3 +1,4 @@
+from collections.abc import AsyncIterator
 from http import HTTPStatus
 from typing import Any
 
@@ -9,6 +10,7 @@
 from dmr.exceptions import EndpointMetadataError
 from dmr.options_mixins import AsyncMetaMixin, MetaMixin
 from dmr.plugins.pydantic import PydanticSerializer
+from dmr.plugins.pydantic.serializer import PydanticEndpointOptimizer
 
 
 def test_controller_either_sync_or_async() -> None:
@@ -174,3 +176,25 @@ def handle_error(
             exc: Exception,
         ) -> Any:
             raise NotImplementedError
+
+
+def test_endpoint_rejects_async_gen() -> None:
+    """Ensure endpoints cannot be async generators."""
+
+    class _NoOpOptimizer(PydanticEndpointOptimizer):
+        @override
+        @classmethod
+        def optimize_endpoint(cls, metadata: Any) -> None:  # noqa: WPS324
+            return None  # noqa: WPS324
+
+    class _NoOpPydanticSerializer(PydanticSerializer):
+        optimizer = _NoOpOptimizer
+
+    with pytest.raises(
+        EndpointMetadataError,
+        match='is an async generator',
+    ):
+
+        class _BadController(Controller[_NoOpPydanticSerializer]):
+            async def get(self) -> AsyncIterator[int]:
+                yield 1  # pragma: no cover

tests/test_unit/test_plugins/test_msgspec/test_validation.py

@@ -1,4 +1,5 @@
 import json
+from collections.abc import AsyncIterator
 from http import HTTPMethod, HTTPStatus
 from typing import final
 
@@ -14,6 +15,7 @@
 from inline_snapshot import snapshot
 
 from dmr import Body, Controller, ResponseSpec, modify, validate
+from dmr.exceptions import EndpointMetadataError
 from dmr.plugins.msgspec import MsgspecSerializer
 from dmr.test import DMRRequestFactory
 
@@ -206,3 +208,15 @@ def test_msgspec_struct_renames_work(
     assert response.status_code == HTTPStatus.CREATED, response.content
     assert response.headers == {'Content-Type': 'application/json'}
     assert json.loads(response.content) == request_data
+
+
+def test_msgspec_rejects_async_gen() -> None:
+    """Ensure msgspec controllers cannot define async generator endpoints."""
+    with pytest.raises(
+        EndpointMetadataError,
+        match='is an async generator',
+    ):
+
+        class _BadController(Controller[MsgspecSerializer]):
+            async def get(self) -> AsyncIterator[int]:
+                yield 1  # pragma: no cover

tests/test_unit/test_streaming/test_sse/test_sync_sse_dev_usage.py

@@ -155,6 +155,9 @@ def test_sync_sse_prod_from_sync_method(
 
 class _SSEWithClose(SSEController[PydanticSerializer]):
     async def get(self) -> AsyncIterator[SSEvent[str | bytes | int]]:
+        return self._events()
+
+    async def _events(self) -> AsyncIterator[SSEvent[str | bytes | int]]:
         yield SSEvent(b'event', serialize=False)
         yield SSEvent(b'second', serialize=False)
         raise StreamingCloseError
@@ -168,7 +171,9 @@ def test_sync_sse_dev_with_close(
     settings.DEBUG = True
     request = dmr_rf.get('/whatever/')
 
-    response = _SSEWithClose.as_view()(request)
+    response: StreamingResponse = async_to_sync(
+        _SSEWithClose.as_view(),  # type: ignore[arg-type]
+    )(request)
 
     assert isinstance(response, StreamingResponse)
     assert response.streaming