The state file is not updated as expected when not using Watson from the CLI

[jnsebgosselin]

From my understanding, the Watson class is instantiated every time a command is called from the CLI, so that the state of the private attributes of Watson._current and Watson._old_state are reinitialized to None after each command.

The problem occurs when using the same instance of Watson to start and stop a task in an event loop or a script. Because the Watson._old_state is never reinitialized to None between commands, its value is never updated. This prevents the update of the sate file in the save method. Below I present a MWE that illustrates this :

import os.path as osp
import os
from watson.watson import Watson

watson = Watson()

# We remove the state file if it exists:

if osp.exists(watson.state_file):
    os.remove(watson.state_file)

print('Watson is started =', watson.is_started)
print(watson._old_state, watson._current, end='\n\n')

# When starting Watson, the content of the state file is updated to
# that of Watson._current:

print('Starting Watson.')
watson.start('test')
print("Saving 'sate' file =", watson._old_state != watson._current)
print(watson._old_state, watson._current)
watson.save()
print(watson._load_json_file(watson.state_file), end='\n\n')

# When stopping, the content of the state file is not updated because
# both Watson._old_state and Watson._current equal {}:

print('Stoping Watson.')
watson.stop()
print("Saving 'sate' file =", watson._old_state != watson._current)
print(watson._old_state, watson._current)
watson.save()
print(watson._load_json_file(watson.state_file), end='\n\n')

# So when we re-initialized Watson, the Watson._current is initialized from the
# content of the state file. Therefore Watson.is_started return True, but it should
# return False:

print('Reinitializing Watson.')
watson = Watson()
print('Watson is started =', watson.is_started)
print(watson._old_state, watson._current)

This results in :

Watson is started = False
{} {}

Starting Watson.
Saving 'sate' file = True
{} {'project': 'test', 'start': <Arrow [2018-07-13T14:50:19.818903-04:00]>, 'tags': [], 'message': None}
{'project': 'test', 'start': 1531507819, 'tags': [], 'message': None}

Stoping Watson.
Saving 'sate' file = False
{} {}
{'project': 'test', 'start': 1531507819, 'tags': [], 'message': None}

Reinitializing Watson.
Watson is started = True
{'project': 'test', 'start': <Arrow [2018-07-13T14:50:19-04:00]>, 'tags': [], 'message': None} {'project': 'test', 'start': <Arrow [2018-07-13T14:50:19-04:00]>, 'tags': [], 'message': None}

Maybe a solution would be to update the value of Watson._old_state every time the state file is saved in the save method here, something like:

safe_save(self.state_file, make_json_writer(lambda: current))
self._old_state = current

[jmaupetit]

Thanks for the report @jnsebgosselin ❤️ I didn't know about your qwatson project, it looks awesome! Can you propose a PR to review for your suggestion?

[jnsebgosselin]

@jmaupetit Sure thing, I can also add a test to cover that corner case if you want.

Also, tyvm for your interest in my current little pet project :)