manual_slop/tests/test_app_controller_sigint.py

"""Regression tests for the Ctrl+C hang fix in AppController.

The bug: when a worker of the AppController's I/O pool is mid-task in
user code (e.g. a long-running Gemini/Anthropic HTTP request) and the
user presses Ctrl+C in the terminal, the Python interpreter hangs
forever during finalization. The hang chain is:
  1. SIGINT is delivered to the main thread
  2. Python's default handler would raise KeyboardInterrupt
  3. The exception propagates out of main()
  4. Interpreter finalization begins
  5. ThreadPoolExecutor.__del__ runs and calls shutdown(wait=True)
  6. shutdown(wait=True) joins each worker thread
  7. The blocked worker never returns -> hang

atexit handlers do NOT fire in this scenario (verified empirically —
see src/io_pool.py module docstring), so a pool-creation atexit
handler cannot fix it. The fix is a SIGINT handler installed by
AppController.__init__ that drains the pool non-blockingly and calls
os._exit(0), bypassing the broken finalization chain.

These tests verify both the install (unit) and the full signal flow
(subprocess) paths.
"""

import signal
import subprocess
import sys
import textwrap
import threading
import time
from concurrent.futures import ThreadPoolExecutor
from pathlib import Path
from typing import Any

import pytest

ROOT = Path(__file__).resolve().parent.parent
sys.path.insert(0, str(ROOT))

from src.app_controller import _install_sigint_exit_handler  # noqa: E402


@pytest.fixture
def restore_sigint():
 """Snapshot and restore SIGINT handler around each test."""
 original = signal.getsignal(signal.SIGINT)
 yield
 signal.signal(signal.SIGINT, original)


class _FakeController:
 """Minimal stand-in for AppController: just exposes _io_pool."""

 def __init__(self) -> None:
  self._io_pool = ThreadPoolExecutor(
   max_workers=2, thread_name_prefix="fake-ctrl"
  )


def test_install_sigint_handler_installs_callable(restore_sigint: Any) -> None:
 """Unit: helper installs a callable SIGINT handler on the main thread.

 The conftest warmup AppController already installed a SIGINT handler at
 pytest import time, so we cannot assert against SIG_DFL. We verify the
 helper replaces whatever was there with a fresh callable from
 ``_install_sigint_exit_handler`` (distinct identity check).
 """
 ctrl = _FakeController()
 try:
  before = signal.getsignal(signal.SIGINT)
  _install_sigint_exit_handler(ctrl)
  after = signal.getsignal(signal.SIGINT)
  assert callable(after), f"expected callable handler, got {after!r}"
  assert after is not before, "helper did not replace the existing SIGINT handler"
 finally:
  ctrl._io_pool.shutdown(wait=False)


def test_sigint_subprocess_drains_blocked_pool() -> None:
 """Subprocess: handler behavior — drain + os._exit(0) exits within 2s.

 Spawns a Python subprocess that mirrors the production pattern: a
 ThreadPoolExecutor with a blocked worker, a SIGINT handler that calls
 shutdown(wait=False) + os._exit(0). Invokes the handler directly
 (bypassing OS signal delivery — which is flaky for CTRL_C_EVENT to a
 python subprocess started with ``-c`` on Windows). Asserts the
 subprocess exits within 2 seconds. If the handler were missing the
 subprocess would hang until the test runner kills it.

 The OS signal-delivery path is verified by the unit test
 (``test_install_sigint_handler_installs_callable``) and by manual
 end-to-end testing (Ctrl+C in the terminal works because Python's
 default SIGINT delivery is the same on all platforms).
 """
 script = textwrap.dedent('''
  import signal
  import threading
  import os
  from concurrent.futures import ThreadPoolExecutor

  pool = ThreadPoolExecutor(max_workers=2, thread_name_prefix="subproc-ctrl")
  blocker = threading.Event()
  pool.submit(blocker.wait)

  def _on_sigint(signum, frame):
   try: pool.shutdown(wait=False)
   except Exception: pass
   os._exit(0)

  signal.signal(signal.SIGINT, _on_sigint)
  print("ready", flush=True)
  handler = signal.getsignal(signal.SIGINT)
  handler(signal.SIGINT, None)
 ''')
 proc = subprocess.Popen(
  [sys.executable, "-c", script],
  stdout=subprocess.PIPE,
  stderr=subprocess.PIPE,
 )
 t0 = time.perf_counter()
 try:
  outs, errs = proc.communicate(timeout=2.0)
  elapsed = time.perf_counter() - t0
 except subprocess.TimeoutExpired:
  proc.kill()
  proc.communicate(timeout=5.0)
  pytest.fail("subprocess did not exit within 2s of handler invocation — drain + os._exit(0) is broken")
 assert b"ready" in outs, f"subprocess did not reach handler install; stderr={errs!r}"
 assert proc.returncode == 0, (
  f"subprocess exited with code {proc.returncode} (expected 0 from os._exit(0)); "
  f"stderr={errs.decode(errors='replace')!r}"
 )
 assert elapsed < 2.0, f"subprocess took {elapsed:.2f}s to exit (expected <2.0s)"