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Fix async generator exception handling and add comprehensive tests

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Lukas
2026-01-19 20:34:06 +01:00
parent d6a82f4329
commit 6d40ddbfe5
3 changed files with 230 additions and 54 deletions
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126
docs/instructions.md
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@@ -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:**
The BackgroundLoaderService was crashing when trying to load series data with the error:
During handling of the above exception, another exception occurred:
```
TypeError: 'async for' requires an object with __aiter__ method, got _AsyncGeneratorContextManager
```
Traceback (most recent call last):
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:**
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`.
**Solution:**
Changed the database session acquisition from:
```python
async for db in get_db_session():
# ... code ...
break # Exit loop after first iteration
```
To the correct pattern:
```python
async with get_db_session() as db:
# ... code ...
```
**Files Modified:**
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
**Tests:**
- ✅ 5 new unit tests for background loader database session handling (all passing)
- ✅ Tests verify proper async context manager usage
- ✅ Tests verify error handling and progress tracking
- ✅ Tests verify episode and NFO loading logic
- ✅ Includes test demonstrating the difference between `async with` and `async for`
**Verification:**
The fix allows the background loader service to properly load series data including episodes, NFO files, logos, and images without crashing.
---
## Next Tasks:
No pending tasks at this time.
Traceback (most recent call last):
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]
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
self.scope, self.receive, self.send
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
)
^
File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/uvicorn/middleware/proxy_headers.py", line 84, in **call**
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**
await super().**call**(scope, receive, send)
File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/applications.py", line 122, in **call**
await self.middleware_stack(scope, receive, send)
File "/home/lukas/miniconda3/envs/AniWorld/lib/python3.13/site-packages/starlette/middleware/errors.py", line 184, in **call**
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)
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)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/lukas/Volume/repo/Aniworld/src/server/middleware/auth.py", line 209, in dispatch
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
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)
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)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/lukas/Volume/repo/Aniworld/src/server/middleware/setup_redirect.py", line 120, in dispatch
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
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)
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()

7
src/server/utils/dependencies.py
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@@ -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
yield session
except (ImportError, RuntimeError):
# Database not available - yield None
yield None

151
tests/unit/test_dependencies.py
View File

@@ -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."""