Use the association proxy instead of the hybrid property

portal/database/models.py

@@ -9,6 +9,7 @@ from typing import List
 
 from flask_sqlalchemy import BaseQuery
 from sqlalchemy import event
+from sqlalchemy.ext.associationproxy import association_proxy
 from sqlalchemy.ext.hybrid import hybrid_property
 from werkzeug.security import check_password_hash, generate_password_hash
 
@@ -888,20 +889,13 @@ class Submission(db.Model, EntityBase):
                              passive_deletes=True, uselist=False)
 
     async_task_id = db.Column(db.String(length=36))
+    course = association_proxy('project', 'course')
 
     @property
     def log_name(self):
         return f"{self.id} ({self.course.codename}/{self.project.codename} for " \
                f"{self.user.username})"
 
-    @hybrid_property
-    def course(self):
-        return self.project.course
-
-    @course.expression
-    def course(cls):
-        return Project.course
-
     def change_state(self, new_state):
         # open to extension (state transition validation, ...)
         self.state = new_state

tests/rest/test_submission.py

@@ -54,7 +54,7 @@ def test_list_all_avail_for_user(rest_service, client):
 
 def test_list_all_avail_for_course(rest_service, client):
     course = rest_service.find.course('testcourse1')
-    db_subm = Submission.query.filter(Submission.course == course.id).all()
+    db_subm = Submission.query.filter(Submission.course == course).all()
     response = utils.make_request(client, f'/submissions?course=testcourse1', method='get')
     assert response.status_code == 200
     assert response.mimetype == 'application/json'
@@ -62,6 +62,7 @@ def test_list_all_avail_for_course(rest_service, client):
     resp_submissions = utils.extract_data(response)
     num_of_submissions = len(resp_submissions)
     assert num_of_submissions == len(db_subm)
+    assert num_of_submissions == 4
 
 
 def test_list_all_avail_for_project(rest_service, client):