claude-code-sdk-python/tests/test_fastapi_streaming_compatibility.py
Lina Tawfik 404c50bce0
Fix FastAPI SSE streaming compatibility (fixes #4)
Remove anyio.create_task_group() from receive_messages() to fix the
RuntimeError "Attempted to exit cancel scope in a different task than
it was entered in" when using the SDK with FastAPI's SSE streaming.

The issue occurred because FastAPI can move async generators between
different asyncio tasks during the streaming lifecycle, which conflicts
with anyio's cancel scope tracking.

Changes:
- Remove task group usage from receive_messages()
- Read stderr sequentially after stdout completes
- Add test to ensure no task groups are used
- Fix existing test expectation for buffer overflow

This is a minimal fix that maintains compatibility while solving the
core issue. The trade-off is that stderr is read after stdout instead
of concurrently, but this is unlikely to cause issues in practice.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>
2025-07-01 00:04:50 -07:00

25 lines
No EOL
1,015 B
Python

"""Test FastAPI streaming compatibility (issue #4 fix)."""
import inspect
from claude_code_sdk._internal.transport.subprocess_cli import SubprocessCLITransport
def test_no_task_groups_in_receive_messages():
"""Verify receive_messages doesn't use task groups (fixes FastAPI issue #4)."""
# Get the source code of receive_messages
source = inspect.getsource(SubprocessCLITransport.receive_messages)
# The fix: ensure no task group or task creation
assert "create_task_group" not in source, (
"receive_messages must not use create_task_group to avoid "
"RuntimeError with FastAPI streaming"
)
assert "asyncio.create_task" not in source, (
"receive_messages must not create tasks to maintain "
"compatibility with FastAPI's generator handling"
)
# Verify stderr is still being read (sequential approach)
assert "_stderr_stream" in source, "Should still read stderr"
assert "stderr_lines" in source, "Should collect stderr output"