warning to install optional dependencies

[clot27]

closes #3391

[Bibo-Joshi]

The changes themself look got to me 👍

• pre-commit is complaining a bit. If you run pre-commit install locally, the pre-commit hooks will run before you can commit
• We'll need a test to ensure that the warning is issued as expected, i.e. the warning is there, the messages is the expected one and the warning points the user to the line where context.job_queue is accessed. You can e.g. have a look at TestJobQueue.test_run_daily for some inspiration on how that can be done :)

[harshil21]

Some stylistic suggestions below.

Also the more likely scenario is when user does application.job_queue.run_* and faces an error. Shouldn't we make that a property to raise this warning as well?

[Bibo-Joshi]

Also the more likely scenario is when user does application.job_queue.run_* and faces an error. Shouldn't we make that a property to raise this warning as well?

I guess it's hard to say if app.job_queue or context.job_queue is used more … but anyway, making Application.job_queue a property and having it issue a warning just like CallbackContext.job_queue sounds like a nice idea :)

[Bibo-Joshi]

Thanks for the updates!

• TestConversationHandler.test_no_running_job_queue_warning currently fails b/c it's trying to override app.job_queue. Maybe it's best to build a new Application instance in that test, i.e. something like

  if not jq:
      app = ApplicationBuilder().token(bot.token).job_queue(None)

• similar for TestConversationHandler.test_schedule_job_exception: here one would do AB().token(…).job_queue(DictJQ())

[harshil21]

okay I'm not sure why Github is not showing me the changes in conversationhandler.py in the files changed tab, but I think you should replace all instances of application.job_queue with application._job_queue to avoid unintentionally raising a warning in user code

[Bibo-Joshi]

I took the liberty to tie up the very last loose ends :) I'm happy now. If harshil is as well, we can merge.

[harshil21]

LGTM