where can i find this file.

This feature would touch a lot of files, mostly involving the Assignment model, along with related controllers and front-end components.

@ragesoss can I take this issue up?

@fillingtothemomo yes, but I think this is a fairly complicated issue that, and it may take a number of iterations to figure out exactly what the implementation should look like.

@ragesoss Can you suggest some newcomer friendly issues for me to work on?

@fillingtothemomo I think you should give #5489 a try. It looks like the other person isn't active on it anymore.

A few clarifications of this issue:

1. This should account for the possibility that the removed article is already present as an Available Article (and should simply remove the article, in that case).
2. This new behavior should only apply to courses that are using Available Articles in the first place, but we don't actually have a good way to detect that option right now. Basically, we want this new behavior only for a course where the instructor chose the 'Instructor prepares a list' option in the assignment wizard. I think a good way to address this would be to add choose_articles_from_list as a tag in the researchwrite/wizard.yml file so that the courses where this should apply will have the choose_articles_from_list Tag. Then the behavior can be controlled on the backend in the controller by determining whether the course has that tag.