Hang when exception is raised in _quit_loop_by_signal

[The-Compiler]

I haven't investigated that closely yet, thought I'd open an issue before I forget.

When raising an exception in _quit_loop_by_signal:

diff --git a/pytestqt/wait_signal.py b/pytestqt/wait_signal.py
index c32a76c..7efc019 100644
--- a/pytestqt/wait_signal.py
+++ b/pytestqt/wait_signal.py
@@ -111,6 +111,7 @@ class SignalBlocker(_AbstractSignalBlocker):
         """
         quits the event loop and marks that we finished because of a signal.
         """
+        raise Exception
         self.signal_triggered = True
         self._loop.quit()
         self._cleanup()

Then pytest-qt's tests seem to hang:

$ tox -e py35-pyqt5 -- tests/test_wait_signal.py -v 
[...]
test_wait_signal.py::test_signal_blocker_exception PASSED
test_wait_signal.py::test_signal_triggered[200-None-True-wait_function0-True] 

[The-Compiler]

I think this is just happening because self._loop.quit() is never called, so we're stuck in the inner event loop, and handling the exception (which happened inside a virtual Qt function) will never be done.

I'm not sure there's anything good we can do about this (other than "don't raise an exception there" 😆), so if you can't think of anything either, I'm fine with closing this.

[nicoddemus]

Perhaps we can make the code more robust to errors by wrapping it into a try/finally:

         """
         quits the event loop and marks that we finished because of a signal.
         """
         try:
             self.signal_triggered = True
             self._cleanup()
         finally:
             self._loop.quit()

[The-Compiler]

I thought about that too and thought it wasn't necessary because I can't imagine there was a condition where self.signal_triggered = True raises.

That being said, I think it's good to have it there as a "reminder" so any future additions (which could maybe raise) are in the try block, so 👍.

[nicoddemus]

I think it's good to have it there as a "reminder" so any future additions

Yeah, that's exactly the intent, less for the current code and more as a reminder for future additions. Sorry for not being explicit. 😄