Only re-enable fauthandler during unconfigure if it was enabled before

src/_pytest/faulthandler.py

@@ -12,6 +12,7 @@ from _pytest.store import StoreKey
 
 
 fault_handler_stderr_key = StoreKey[TextIO]()
+fault_handler_originally_enabled_key = StoreKey[bool]()
 
 
 def pytest_addoption(parser: Parser) -> None:
@@ -27,6 +28,7 @@ def pytest_configure(config: Config) -> None:
 
     stderr_fd_copy = os.dup(get_stderr_fileno())
     config._store[fault_handler_stderr_key] = open(stderr_fd_copy, "w")
+    config._store[fault_handler_originally_enabled_key] = faulthandler.is_enabled()
     faulthandler.enable(file=config._store[fault_handler_stderr_key])
 
 
@@ -38,10 +40,9 @@ def pytest_unconfigure(config: Config) -> None:
     if fault_handler_stderr_key in config._store:
         config._store[fault_handler_stderr_key].close()
         del config._store[fault_handler_stderr_key]
-    # Re-enable the faulthandler, attaching it to the default sys.stderr
-    # so we can see crashes after pytest has finished, usually during
-    # garbage collection during interpreter shutdown.
-    faulthandler.enable(file=get_stderr_fileno())
+    if config._store.get(fault_handler_originally_enabled_key, False):
+        # Re-enable the faulthandler if it was originally enabled.
+        faulthandler.enable(file=get_stderr_fileno())
 
 
 def get_stderr_fileno() -> int:

testing/test_faulthandler.py

@@ -19,22 +19,41 @@ def test_enabled(pytester: Pytester) -> None:
     assert result.ret != 0
 
 
-def test_crash_near_exit(pytester: Pytester) -> None:
-    """Test that fault handler displays crashes that happen even after
-    pytest is exiting (for example, when the interpreter is shutting down)."""
+def setup_crashing_test(pytester: Pytester) -> None:
     pytester.makepyfile(
         """
-    import faulthandler
-    import atexit
-    def test_ok():
-        atexit.register(faulthandler._sigabrt)
-    """
+        import faulthandler
+        import atexit
+        def test_ok():
+            atexit.register(faulthandler._sigabrt)
+        """
     )
-    result = pytester.runpytest_subprocess()
+
+
+def test_crash_during_shutdown_captured(pytester: Pytester) -> None:
+    """
+    Re-enable faulthandler if pytest encountered it enabled during configure.
+    We should be able to then see crashes during interpreter shutdown.
+    """
+    setup_crashing_test(pytester)
+    args = (sys.executable, "-Xfaulthandler", "-mpytest")
+    result = pytester.run(*args)
     result.stderr.fnmatch_lines(["*Fatal Python error*"])
     assert result.ret != 0
 
 
+def test_crash_during_shutdown_not_captured(pytester: Pytester) -> None:
+    """
+    Check that pytest leaves faulthandler disabled if it was not enabled during configure.
+    This prevents us from seeing crashes during interpreter shutdown (see #8260).
+    """
+    setup_crashing_test(pytester)
+    args = (sys.executable, "-mpytest")
+    result = pytester.run(*args)
+    result.stderr.no_fnmatch_line("*Fatal Python error*")
+    assert result.ret != 0
+
+
 def test_disabled(pytester: Pytester) -> None:
     """Test option to disable fault handler in the command line."""
     pytester.makepyfile(