Fix issue 324 (#329)

Author: Shigerman

cadwyn/applications.py

@@ -260,11 +260,16 @@ async def __call__(self, scope: Any, receive: Any, send: Any) -> None:
         await self.__call__(scope, receive, send)
 
     def _cadwyn_initialize(self) -> None:
-        generated_routers = generate_versioned_routers(
-            self._latest_version_router,
-            webhooks=self.webhooks,
-            versions=self.versions,
-        )
+        try:
+            generated_routers = generate_versioned_routers(
+                self._latest_version_router,
+                webhooks=self.webhooks,
+                versions=self.versions,
+            )
+        except RecursionError as e:
+            raise ImportError(
+                "You are likely missing an import from typing such as typing.Literal which causes RecursionError"
+            ) from e
         for version, router in generated_routers.endpoints.items():
             self._add_versioned_routers(router, version=version)
 

tests/test_router_generation_missing_import.py

@@ -0,0 +1,55 @@
+"""The test is kept in a separate file to avoid accidental importing of Literal"""
+
+from __future__ import annotations
+
+from typing import Annotated  # Note: _no_ import of Literal. This triggers the bug!
+
+import fastapi
+import pytest
+from fastapi import Depends
+from fastapi.testclient import TestClient
+from pydantic import BaseModel, Field
+
+import cadwyn
+from cadwyn import current_dependency_solver
+from cadwyn.applications import Cadwyn
+from cadwyn.route_generation import VersionedAPIRouter
+from cadwyn.structure.schemas import schema
+from cadwyn.structure.versions import Version, VersionBundle, VersionChange
+
+
+def test__missing_an_import_used_in_annotations_with_from_future_import_annotations():
+    """Regression test for https://github.com/zmievsa/cadwyn/issues/324"""
+
+    class MySchema(BaseModel):
+        foo: str = Field(coerce_numbers_to_str=True)
+
+    class MyVersionChange(VersionChange):
+        description = "Hello"
+        instructions_to_migrate_to_previous_version = (
+            schema(MySchema).field("foo").had(type=int),
+            schema(MySchema).field("foo").didnt_have("coerce_numbers_to_str"),
+        )
+
+    app = Cadwyn(versions=VersionBundle(Version("2001-01-01", MyVersionChange), Version("2000-01-01")))
+    router = VersionedAPIRouter()
+
+    async def dep_with_solver(
+        dependency_solver: Annotated[Literal[fastapi, cadwyn], Depends(current_dependency_solver)],  # noqa: F821  # pyright: ignore[reportUndefinedVariable]
+    ):
+        pass
+
+    @router.post(
+        "/test",
+        dependencies=[Depends(dep_with_solver)],
+    )
+    async def route_with_inner_schema_forwardref(dep: MySchema) -> MySchema:
+        return dep
+
+    app.generate_and_include_versioned_routers(router)
+    client_2000 = TestClient(app, headers={app.router.api_version_parameter_name: "2000-01-01"})
+    with pytest.raises(
+        ImportError,
+        match="You are likely missing an import from typing such as typing.Literal which causes RecursionError",
+    ):
+        assert client_2000.post("/test", json={"foo": 1}).json() == {"foo": 1}