Let a course nobody is assigned to be graded

[vikrantwiz02]

Symptom

Uploading a grade sheet for PR3003 — Optional Project answers:

No students are registered in the selected section for this course.

while the very same screen lists the student as Registered — because that preview table is built client-side from the CSV, so it shows a roster the server has already rejected.

Cause

The course has no offering at all, and every one of its registrations therefore carries none:

reg: PR3003  sem=6  Regular  session='2025-26'  Even Semester
     course_instructor=None  section=None
offerings for PR3003: 0
registrations of PR3003: 86 | without an offering: 86

The roster in UploadGradesProfAPI narrows by section like this:

my_sections = {o.section_label for o in my_offerings}   # empty: no offerings exist
if programme_type == "UG" and None not in my_sections:
    regs = regs.filter(
        Q(course_instructor_id__in=my_offering_ids)                                     # empty
        | (Q(course_instructor__isnull=True) & Q(student_id__section__in=my_sections))   # empty
    )

Its own comment says a no-section (elective) offering owns all registrants — the None in my_sections case. But an empty set also satisfies None not in my_sections, so for a course with no offering the filter runs with two empty sets, matches nothing, and reports the roster as empty.

Fix

Require that a section actually exists before narrowing:

if programme_type == "UG" and my_sections and None not in my_sections:

A course with no offering now behaves like a no-section elective and owns all of its registrants. Sectioned courses are untouched, their set of sections being non-empty.

Verified through the real endpoint with the actual grade sheet: POST /examination/api/upload_grades_prof/ for PR3003, 2025-26 Even, returns 200 where it returned 400. The grade row that test wrote was removed afterwards; PR3003 is back to its 57 historical rows with none for 2025-26.

manage.py check clean, no migrations.

Worth a separate look

This is also a data condition: 86 students are registered in a course with no instructor assigned, so nothing in Course Instructors records who owns it. Grading works now regardless, but on the faculty side a professor with no offering still gets "Access denied: you are not assigned to teach this course this term" — correct by the letter, confusing for whoever actually supervises those projects.