Fixing any_unfulfilled_milestones in mobile course_enrollments API

[iamjazzar]

Description

In User Course Enrollments List, if we enabled Entrance Exam from Schedule & Details section and then re-desabling it, thecourseware_access field in the API will keep preventing the student from showing the course on the mobile apps.

            "courseware_access": {
                "has_access": false,
                "error_code": "unfulfilled_milestones",
                "developer_message": "User has unfulfilled milestones",
                "user_message": "User has unfulfilled milestones."
            },

This problem is happening because the get_course_milestones_fulfillment_paths method in the milestones API is returning an empty dictionary {} if the course doesn't have any milestones, after enabling Entrance Exam it returns a complex dict-of-dicts like this:

{
  "course-v1:org+course+run.entrance_exams.Completed Course Entrance Exam": {
     "content": [
          "block-v1:org+course+run+type@chapter+block@cd5f1b8bef874bcdad80b2857f5aeffd"
     ]
  }
}

While redoubling the entrance exam causes the method to return the previously-enabled prerequisites with an empty dictionary like this:

{"course-v1:org+course+run.entrance_exams.Completed Course Entrance Exam": {}}

The method any_unfulfilled_milestones is not addressing this scenario, so what I did is checking that every value in the dict returned from get_course_milestones_fulfillment_paths, if any value has a non-empty dictionary then the student is still having unfulfilled milestones and we are returning True, if the dictionary is empty or the student have fulfilled the milestones then we are returning False.

Notes

1. This solution won't affect the result if the learner completed the prerequisites since the get_course_milestones_fulfillment_paths will return an empty dictionary if the Entrance Exam fulfilled.
2. EdX PR: #14758

Update

Another issue arised as if the instructor enabled and disabled the Prerequisite Course in Studio's Requirements section, the course became inaccessible for learner in the dashboard and the API views.
This happens because selecting None from the dropdown list in Studio has no functionality in the code.

[Salomari1987]

I think this calls for an OSPR, please contribute it to edX and cherry pick

[Salomari1987]

Just one comment, why not use the function in this file: get_course_milestones_fulfillment_paths ?
I see in some functions the milestones_api.get_course_..... is being used, and only in one function the get_course_milestones_fulfillment_paths in the file is being used. I do not see the difference in the result on one hand, and I do not see why from milestones import api as milestones_api has to be used many times?

[iamjazzar]

The other methods are using the API gateway, so I prefer keeping it like this. In the same hand, the get_course_milestones_fulfillment_paths function is rechecking the feature flag again, a reason that tells not call it.

Let's wait for edX's review and see. But we still need to know the status of the changes if we need had to merge this before edX do.

[Salomari1987]

@AhmedAljazzar ping

[iamjazzar]

@Salomari1987 pong.

[Salomari1987]

@AhmedAljazzar this works fine as expected, however when tried for course prerequisites, the has_access field will become false for the nonsuperuser. Please fix it also for course prerequisites.

[Salomari1987]

and rebase

[iamjazzar]

@Salomari1987 Done :)

[iamjazzar]

@Salomari1987, @halawa : This needs approval if you have time.

[OmarIthawi]

I'll take it!

[iamjazzar]

Great!

[OmarIthawi]

Smoke tested it and it works. The code looks fine although I haven't tested it rigorously.