Fix Linux pytest shutdown with explicit Julia signal handling

CHANGELOG.md

@@ -1,6 +1,7 @@
 # Changelog
 
 ## Unreleased
+* Bug fix: on Linux, coordinate pytest's diagnostic plugin with explicitly enabled Julia signal handling to prevent shutdown crashes.
 * Bug fix: avoid precompilation cache miss when `check_bounds` option set.
 * Bug fix: `juliacall` set the environment variable `JULIA_PYTHONCALL_EXECUTABLE`
   instead of `JULIA_PYTHONCALL_EXE`, so child Julia processes resolved a new

pyproject.toml

@@ -15,6 +15,9 @@ classifiers = [
 requires-python = ">=3.10, <4"
 dependencies = ["juliapkg >=0.1.26, <0.2"]
 
+[project.entry-points.pytest11]
+juliacall = "juliacall_pytest"
+
 [dependency-groups]
 dev = [
     "flake8>=5.0",
@@ -25,4 +28,4 @@ dev = [
 ]
 
 [tool.hatch.build.targets.wheel]
-packages = ["pysrc/juliacall"]
+packages = ["pysrc/juliacall", "pysrc/juliacall_pytest"]

pysrc/juliacall_pytest/__init__.py

@@ -0,0 +1,36 @@
+import os
+import sys
+
+import pytest
+
+
+@pytest.hookimpl(tryfirst=True)
+def pytest_load_initial_conftests(early_config):
+    handle_signals = sys._xoptions.get("juliacall-handle-signals")
+    if handle_signals is None:
+        handle_signals = os.environ.get("PYTHON_JULIACALL_HANDLE_SIGNALS")
+    if sys.platform != "linux" or handle_signals != "yes":
+        return
+    if not early_config.pluginmanager.hasplugin("faulthandler"):
+        return
+    try:
+        exit_on_timeout = early_config.getini("faulthandler_exit_on_timeout")
+    except ValueError as error:
+        if not isinstance(error.__cause__, KeyError) or error.__cause__.args != ("faulthandler_exit_on_timeout",):
+            raise
+        # Older pytest versions have no exit-on-timeout option.
+        exit_on_timeout = False
+    if exit_on_timeout and float(early_config.getini("faulthandler_timeout")) > 0:
+        raise pytest.UsageError(
+            "Julia signal handling conflicts with pytest's faulthandler_exit_on_timeout. "
+            "Use an external process timeout instead."
+        )
+    early_config.pluginmanager.set_blocked("faulthandler")
+    early_config.issue_config_time_warning(
+        pytest.PytestConfigWarning(
+            "Julia signal handling is enabled: disabling pytest's faulthandler plugin "
+            "and its timeout diagnostics to preserve Julia's signal handlers. "
+            "Julia fatal diagnostics remain enabled. Use -p no:juliacall to opt out."
+        ),
+        stacklevel=2,
+    )

pytest/test_signals.py

@@ -0,0 +1,67 @@
+import os
+import subprocess
+import sys
+
+import pytest
+
+
+@pytest.mark.skipif(sys.platform != "linux", reason="Linux signal handling")
+def test_pytest_shutdown(tmp_path):
+    test_file = tmp_path / "test_shutdown.py"
+    test_file.write_text('''
+import atexit
+from juliacall import Main as jl
+
+atexit.register(lambda: print("PYTHON_ATEXIT", flush=True))
+jl.seval("""
+atexit(() -> println("JULIA_ATEXIT"))
+const retained = Ref(0)
+finalizer(x -> println("JULIA_FINALIZER"), retained)
+""")
+
+def test_gc():
+    jl.seval("Threads.@threads for i in 1:100; zeros(10000); GC.gc(); end")
+''')
+    env = dict(os.environ, PYTHON_JULIACALL_HANDLE_SIGNALS="yes", PYTHON_JULIACALL_THREADS="6")
+    env.pop("PYTEST_ADDOPTS", None)
+    result = subprocess.run(
+        [sys.executable, "-m", "pytest", "-s", "-q", str(test_file)],
+        env=env, capture_output=True, text=True, timeout=120,
+    )
+    assert result.returncode == 0, result.stdout + result.stderr
+    for marker in ("PYTHON_ATEXIT", "JULIA_ATEXIT", "JULIA_FINALIZER"):
+        assert marker in result.stdout
+
+
+@pytest.mark.skipif(sys.platform != "linux", reason="Linux signal handling")
+@pytest.mark.parametrize("setting,xoption,plugins,enabled", [
+    (None, None, [], True),
+    ("no", None, [], True),
+    ("yes", None, [], False),
+    ("yes", "no", [], True),
+    ("no", "yes", [], False),
+    ("yes", "", [], True),
+    ("yes", "invalid", [], True),
+    ("yes", None, ["-p", "no:juliacall"], True),
+])
+def test_pytest_configuration(tmp_path, setting, xoption, plugins, enabled):
+    test_file = tmp_path / "test_configuration.py"
+    test_file.write_text(f'''
+import faulthandler
+import sys
+
+def test_configuration():
+    assert "juliacall" not in sys.modules
+    assert faulthandler.is_enabled() is {enabled!r}
+''')
+    env = dict(os.environ)
+    for name in ("PYTEST_ADDOPTS", "PYTHONFAULTHANDLER", "PYTHON_JULIACALL_HANDLE_SIGNALS"):
+        env.pop(name, None)
+    if setting is not None:
+        env["PYTHON_JULIACALL_HANDLE_SIGNALS"] = setting
+    command = [sys.executable]
+    if xoption is not None:
+        command += ["-X", "juliacall-handle-signals" + ("=" + xoption if xoption else "")]
+    command += ["-m", "pytest", "-q", *plugins, str(test_file)]
+    result = subprocess.run(command, env=env, capture_output=True, text=True, timeout=30)
+    assert result.returncode == 0, result.stdout + result.stderr