The logger method in Application interface terminates python

[OllieKampo]

According to the clingo api documentation 5.4 for python (https://potassco.org/clingo/python-api/5.4/) you can use the method:

def logger(self, code: MessageCode, message: str) -> None:

Within the Application interface to intercept messages normally printed to standard error.
I am trying to use this, but whenever my Application class implements this method python terminates almost immediately after any calls to control.ground(parts).

For example:

def logger(self, code: clingo.MessageCode, message: str) -> None:
        self._data.get_logger().add_log("TEST", message)

def main(self, control: clingo.Control, files: List[str]):
        self.__build_program(control)
        start_time: float = time.clock()
        self._data.get_logger().add_log("ASP_SYSTEM", "Grounder invoked")
        if self.is_planning_mode:
            control.ground([("base", []), ("planning_module", []), ("recorded_history", [])])
        else:
            control.ground([("base", []), ("diagnostics_module", []), ("recorded_history", [])])
        self._data.get_logger().add_log("ASP_SYSTEM", "Grounder returned (duration {0} seconds)".format(time.clock() - start_time))
        start_time = time.clock()
        self._data.get_logger().add_log("ASP_SYSTEM", "Solver invoked")
        handle: clingo.SolveHandle
        with control.solve(on_model = self.on_model, on_finish = self.on_finish, async_ = True) as handle:
            while not handle.wait(0.1):
                for cursor in '\\|/-':
                    sys.stdout.write('\r{0}'.format(cursor))
                    sys.stdout.flush()
            self._data.get_logger().add_log("ASP_SYSTEM",
                                            "Solver returned {0} with {1} (duration {2} seconds)".format(handle.get(),
                                                                                                         "OPTIMUM FOUND" if handle.get().exhausted else "OPTIMUM NOT FOUND",
                                                                                                         time.clock() - start_time))

def __build_program(self, control: clingo.Control) -> None:
        builder: clingo.ProgramBuilder
        with control.builder() as builder:
            part: ast.AST
            for part in self.__program:
                builder.add(part)

Will print [23:11:31] ASP_SYSTEM: Grounder invoked and then immediately terminate python.
I have tried surrounding the grounder call with a try/except block but this does not work.
I cannot understand the problem at all, it does not seem to throw any sort of error or exception, it just terminates python...

Note that if I comment out the logger method it runs exactly as expected, no errors.

Any ideas?

[rkaminsk]

Thanks for reporting. The problem is fixed in the wip branch. See the linked commit. The next release will still take a little because there are some further things I want to address.

[OllieKampo]

Excellent, thank you :)