hotjar.py

from functools import wraps


def log(utf8_string, tags):
    # do some logging
    pass


def log_on_exception(*tags):
    """Decorate a function to log any exception it raises.

    This decorator provides functionality to log a message
    when an exception is raised from within the decorated
    function.

    :param tags: a sequence of tags
    :return: the result of the function it wraps
    """

    def func_decor(func):

        @wraps(func)
        def wrapper(*args, **kwargs):

            try:
                func_result = func(*args, **kwargs)

            except Exception as e:
                error_msg = getattr(e, 'message', repr(e))
                log(error_msg, tags)

                # re-raise exception
                raise

            return func_result

        return wrapper

    return func_decor

test_hotjar.py

import unittest

from hotjar import log_on_exception


@log_on_exception('tag1', 'tag2')
def raising_func():

    raise NotImplementedError


def normal_func():

    return 'random value'


class HotjarTestCase(unittest.TestCase):

    def test_log_on_exception_raise(self):

        with self.assertRaises(NotImplementedError):
            raising_func()

    def test_log_on_exception_return_value(self):
        """Ensure that the decorator's return value is
        that of the function assuming no error is raised."""

        undecorated_func_result = normal_func()

        decorated_func_result = log_on_exception('tag1', 'tag2')(normal_func)()

        self.assertEqual(undecorated_func_result, decorated_func_result)


if __name__ == '__main__':
    unittest.main()