Fix async generator exception handling and add comprehensive tests

docs/instructions.md

@@ -119,56 +119,86 @@ For each task completed:
 
 ## TODO List:
 
-✅ **Task Completed Successfully**
+fix:
 
-### Issue Fixed: TypeError: 'async for' requires an object with **aiter** method
+INFO: 127.0.0.1:34916 - "POST /api/anime/search HTTP/1.1" 200
+INFO: 127.0.0.1:34916 - "POST /api/anime/add HTTP/1.1" 500
+ERROR: Exception in ASGI application
+Traceback (most recent call last):
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/anyio/streams/memory.py", line 98, in receive
+return self.receive_nowait()
+~~~~~~~~~~~~~~~~~~~^^
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/anyio/streams/memory.py", line 93, in receive_nowait
+raise WouldBlock
+anyio.WouldBlock
 
-**Problem:**
+During handling of the above exception, another exception occurred:
-The BackgroundLoaderService was crashing when trying to load series data with the error:
 
-```
+Traceback (most recent call last):
-TypeError: 'async for' requires an object with __aiter__ method, got _AsyncGeneratorContextManager
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/middleware/base.py", line 78, in call_next
-```
+message = await recv_stream.receive()
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/anyio/streams/memory.py", line 118, in receive
+raise EndOfStream
+anyio.EndOfStream
 
-This error occurred in `_load_series_data` method at line 282 of [background_loader_service.py](src/server/services/background_loader_service.py).
+During handling of the above exception, another exception occurred:
 
-**Root Cause:**
+Traceback (most recent call last):
-The code was incorrectly using `async for db in get_db_session():` to get a database session. However, `get_db_session()` is decorated with `@asynccontextmanager`, which returns an async context manager (not an async iterator). Async context managers must be used with `async with`, not `async for`.
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/uvicorn/protocols/http/httptools_impl.py", line 426, in run_asgi
-
+result = await app( # type: ignore[func-returns-value]
-**Solution:**
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-Changed the database session acquisition from:
+self.scope, self.receive, self.send
-
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-```python
+)
-async for db in get_db_session():
+^
-    # ... code ...
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/uvicorn/middleware/proxy_headers.py", line 84, in **call**
-    break  # Exit loop after first iteration
+return await self.app(scope, receive, send)
-```
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/fastapi/applications.py", line 1106, in **call**
-To the correct pattern:
+await super().**call**(scope, receive, send)
-
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/applications.py", line 122, in **call**
-```python
+await self.middleware_stack(scope, receive, send)
-async with get_db_session() as db:
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/middleware/errors.py", line 184, in **call**
-    # ... code ...
+raise exc
-```
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/middleware/errors.py", line 162, in **call**
-
+await self.app(scope, receive, \_send)
-**Files Modified:**
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/middleware/base.py", line 108, in **call**
-
+response = await self.dispatch_func(request, call_next)
-1. [src/server/services/background_loader_service.py](src/server/services/background_loader_service.py) - Fixed async context manager usage
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-2. [tests/unit/test_background_loader_session.py](tests/unit/test_background_loader_session.py) - Created comprehensive unit tests
+File "/home/lukas/Volume/repo/Aniworld/src/server/middleware/auth.py", line 209, in dispatch
-
+return await call_next(request)
-**Tests:**
+^^^^^^^^^^^^^^^^^^^^^^^^
-
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/middleware/base.py", line 84, in call_next
-- ✅ 5 new unit tests for background loader database session handling (all passing)
+raise app_exc
-- ✅ Tests verify proper async context manager usage
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/middleware/base.py", line 70, in coro
-- ✅ Tests verify error handling and progress tracking
+await self.app(scope, receive_or_disconnect, send_no_error)
-- ✅ Tests verify episode and NFO loading logic
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/middleware/base.py", line 108, in **call**
-- ✅ Includes test demonstrating the difference between `async with` and `async for`
+response = await self.dispatch_func(request, call_next)
-
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-**Verification:**
+File "/home/lukas/Volume/repo/Aniworld/src/server/middleware/setup_redirect.py", line 120, in dispatch
-The fix allows the background loader service to properly load series data including episodes, NFO files, logos, and images without crashing.
+return await call_next(request)
-
+^^^^^^^^^^^^^^^^^^^^^^^^
----
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/middleware/base.py", line 84, in call_next
-
+raise app_exc
-## Next Tasks:
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/middleware/base.py", line 70, in coro
-
+await self.app(scope, receive_or_disconnect, send_no_error)
-No pending tasks at this time.
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/middleware/cors.py", line 91, in **call**
+await self.simple_response(scope, receive, send, request_headers=headers)
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/middleware/cors.py", line 146, in simple_response
+await self.app(scope, receive, send)
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/middleware/exceptions.py", line 79, in **call**
+raise exc
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/middleware/exceptions.py", line 68, in **call**
+await self.app(scope, receive, sender)
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/fastapi/middleware/asyncexitstack.py", line 14, in **call**
+async with AsyncExitStack() as stack:
+~~~~~~~~~~~~~~^^
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/contextlib.py", line 768, in **aexit**
+raise exc
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/contextlib.py", line 751, in **aexit**
+cb_suppress = await cb(\*exc_details)
+^^^^^^^^^^^^^^^^^^^^^^
+File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/contextlib.py", line 271, in **aexit**
+raise RuntimeError("generator didn't stop after athrow()")
+RuntimeError: generator didn't stop after athrow()

src/server/utils/dependencies.py

@@ -170,12 +170,7 @@ async def get_optional_database_session() -> AsyncGenerator:
         from src.server.database import get_db_session
         
         async with get_db_session() as session:
-            try:
             yield session
-            except Exception:
-                # Re-raise the exception to let FastAPI handle it
-                # This prevents "generator didn't stop after athrow()" error
-                raise
     except (ImportError, RuntimeError):
         # Database not available - yield None
         yield None

tests/unit/test_dependencies.py

@@ -16,6 +16,7 @@ from src.server.utils.dependencies import (
     common_parameters,
     get_current_user,
     get_database_session,
+    get_optional_database_session,
     get_series_app,
     log_request_dependency,
     optional_auth,
@@ -291,6 +292,156 @@ class TestUtilityDependencies:
         # Assert - no exception should be raised
 
 
+class TestOptionalDatabaseSession:
+    """Test cases for optional database session dependency."""
+
+    @pytest.mark.asyncio
+    async def test_optional_database_session_success(self):
+        """Test successful database session creation."""
+        from unittest.mock import AsyncMock
+
+        # Mock the database session
+        mock_session = AsyncMock()
+        mock_session.__aenter__ = AsyncMock(return_value=mock_session)
+        mock_session.__aexit__ = AsyncMock(return_value=None)
+        
+        mock_get_db = Mock(return_value=mock_session)
+
+        with patch('src.server.database.get_db_session', mock_get_db):
+            # Act
+            gen = get_optional_database_session()
+            session = await gen.__anext__()
+
+            # Assert
+            assert session is mock_session
+            mock_get_db.assert_called_once()
+
+            # Cleanup
+            try:
+                await gen.aclose()
+            except StopAsyncIteration:
+                pass
+
+    @pytest.mark.asyncio
+    async def test_optional_database_session_not_available(self):
+        """Test when database is not available (ImportError)."""
+        # Mock ImportError when trying to import get_db_session
+        with patch(
+            'src.server.database.get_db_session',
+            side_effect=ImportError("No module named 'database'")
+        ):
+            # Act
+            gen = get_optional_database_session()
+            session = await gen.__anext__()
+
+            # Assert - should return None when database not available
+            assert session is None
+
+            # Cleanup
+            try:
+                await gen.aclose()
+            except StopAsyncIteration:
+                pass
+
+    @pytest.mark.asyncio
+    async def test_optional_database_session_runtime_error(self):
+        """Test when database raises RuntimeError."""
+        # Mock RuntimeError when trying to get database session
+        with patch(
+            'src.server.database.get_db_session',
+            side_effect=RuntimeError("Database connection failed")
+        ):
+            # Act
+            gen = get_optional_database_session()
+            session = await gen.__anext__()
+
+            # Assert - should return None on RuntimeError
+            assert session is None
+
+            # Cleanup
+            try:
+                await gen.aclose()
+            except StopAsyncIteration:
+                pass
+
+    @pytest.mark.asyncio
+    async def test_optional_database_session_exception_during_use(self):
+        """
+        Test that exceptions during database operations are properly propagated.
+        
+        This test specifically addresses the "generator didn't stop after athrow()"
+        error that occurred when exceptions were caught and re-raised within the
+        yield block of an async context manager.
+        """
+        from unittest.mock import AsyncMock
+
+        # Create a mock session that will raise an exception when used
+        mock_session = AsyncMock()
+        mock_session.__aenter__ = AsyncMock(return_value=mock_session)
+        mock_session.__aexit__ = AsyncMock(return_value=None)
+        
+        # Mock the get_db_session to return our mock session
+        mock_get_db = Mock(return_value=mock_session)
+
+        with patch('src.server.database.get_db_session', mock_get_db):
+            # Act & Assert
+            gen = get_optional_database_session()
+            session = await gen.__anext__()
+            
+            assert session is mock_session
+            
+            # Simulate an exception being thrown into the generator
+            # This mimics what happens when an endpoint raises an exception
+            # after the dependency has yielded
+            test_exception = ValueError("Database operation failed")
+            
+            try:
+                # This should not cause "generator didn't stop after athrow()" error
+                await gen.athrow(test_exception)
+                # If we get here, the exception was swallowed (shouldn't happen)
+                pytest.fail("Exception should have been propagated")
+            except ValueError as e:
+                # Exception should be properly propagated
+                assert str(e) == "Database operation failed"
+            except StopAsyncIteration:
+                # Generator stopped normally after exception
+                pass
+
+    @pytest.mark.asyncio
+    async def test_optional_database_session_cleanup_on_exception(self):
+        """Test that database session is properly cleaned up when exception occurs."""
+        from unittest.mock import AsyncMock
+
+        # Track cleanup
+        cleanup_called = []
+        
+        async def mock_exit(*args):
+            cleanup_called.append(True)
+            return None
+
+        # Create a mock session with tracked cleanup
+        mock_session = AsyncMock()
+        mock_session.__aenter__ = AsyncMock(return_value=mock_session)
+        mock_session.__aexit__ = mock_exit
+        
+        mock_get_db = Mock(return_value=mock_session)
+
+        with patch('src.server.database.get_db_session', mock_get_db):
+            gen = get_optional_database_session()
+            session = await gen.__anext__()
+            
+            assert session is mock_session
+            
+            # Throw an exception to simulate endpoint failure
+            try:
+                await gen.athrow(RuntimeError("Simulated endpoint error"))
+            except (RuntimeError, StopAsyncIteration):
+                pass
+            
+            # Assert cleanup was called
+            assert len(cleanup_called) > 0, "Session cleanup should have been called"
+
+
 class TestIntegrationScenarios:
     """Integration test scenarios for dependency injection."""