Merge branch '308-sqlalchemy-cascades' into 'master'

Use SQLAlchemy cascades for deleting objects

Closes #308

See merge request zesje/zesje!160

tests/conftest.py

 import os
 
 import pytest
+from flask import Flask
+from zesje.api import api_bp
+from zesje.database import db
 
 
 # Adapted from https://stackoverflow.com/a/46062148/1062698
 @pytest.fixture
 def datadir():
     return os.path.join(os.path.dirname(os.path.abspath(__file__)), 'data')
+
+
+@pytest.fixture(scope="module")
+def app():
+    app = Flask(__name__, static_folder=None)
+
+    app.config.update(
+        SQLALCHEMY_DATABASE_URI='sqlite:///:memory:',
+        SQLALCHEMY_TRACK_MODIFICATIONS=False  # Suppress future deprecation warning
+    )
+    db.init_app(app)
+
+    with app.app_context():
+        db.create_all()
+
+    app.register_blueprint(api_bp, url_prefix='/api')
+
+    return app
+
+
+@pytest.fixture
+def empty_app(app):
+    with app.app_context():
+        db.drop_all()
+        db.create_all()
+
+    return app

tests/test_database.py

 import pytest
 from flask import Flask
 
-from zesje.database import db, Exam, _generate_exam_token
+from zesje.database import db, _generate_exam_token, Exam, Problem, ProblemWidget, Solution
+from zesje.database import Submission, Scan, Page, ExamWidget, FeedbackOption
 
 
 @pytest.mark.parametrize('duplicate_count', [
@@ -32,3 +33,141 @@ def test_exam_generate_token_length_uppercase(duplicate_count, monkeypatch):
         id = _generate_exam_token()
         assert len(id) == 12
         assert id.isupper()
+
+
+def test_cascades_exam(empty_app, exam, problem, submission, scan, exam_widget):
+    """Tests the cascades defined for an exam
+
+    Tests the cascades for the following relations:
+    - Exam -> Submission
+    - Exam -> Problem
+    - Exam -> Scan
+    - Exam -> ExamWidget
+    """
+    empty_app.app_context().push()
+    exam.problems = [problem]
+    exam.scans = [scan]
+    exam.submissions = [submission]
+    exam.widgets = [exam_widget]
+
+    db.session.add(exam)
+    db.session.commit()
+
+    assert problem in db.session
+    assert submission in db.session
+    assert scan in db.session
+    assert exam_widget in db.session
+
+    db.session.delete(exam)
+    db.session.commit()
+
+    assert problem not in db.session
+    assert submission not in db.session
+    assert scan not in db.session
+    assert exam_widget not in db.session
+
+
+def test_cascades_problem(empty_app, exam, problem, submission, solution, problem_widget, feedback_option):
+    """Tests the cascades defined for a problem
+
+    Tests the cascades for the following relations:
+    - Problem -> Solution
+    - Problem -> ProblemWidget
+    - Problem -> FeedbackOption
+    """
+    empty_app.app_context().push()
+
+    exam.problems = [problem]
+    exam.submissions = [submission]
+    solution.submission = submission
+    problem.widget = problem_widget
+    problem.solutions = [solution]
+    problem.feedback_options = [feedback_option]
+
+    db.session.add_all([exam, problem, submission])
+    db.session.commit()
+
+    assert solution in db.session
+    assert problem_widget in db.session
+    assert feedback_option in db.session
+
+    db.session.delete(problem)
+    db.session.commit()
+
+    assert solution not in db.session
+    assert problem_widget not in db.session
+    assert feedback_option not in db.session
+
+
+def test_cascades_submission(empty_app, exam, problem, submission, solution, page):
+    """Tests the cascades defined for a submission
+
+    Tests the cascades for the following relations:
+    - Submission -> Solution
+    - Submission -> Page
+    """
+    empty_app.app_context().push()
+
+    exam.problems = [problem]
+    exam.submissions = [submission]
+
+    solution.problem = problem
+    solution.submission = submission
+    page.submission = submission
+
+    db.session.add_all([exam, problem, submission])
+    db.session.commit()
+
+    assert solution in db.session
+    assert page in db.session
+
+    db.session.delete(submission)
+    db.session.commit()
+
+    assert solution not in db.session
+    assert page not in db.session
+
+
+@pytest.fixture
+def exam():
+    return Exam(name='')
+
+
+@pytest.fixture
+def problem():
+    return Problem(name='')
+
+
+@pytest.fixture
+def problem_widget():
+    return ProblemWidget(name='', page=0, x=0, y=0, width=0, height=0)
+
+
+@pytest.fixture
+def exam_widget():
+    return ExamWidget(name='', x=0, y=0)
+
+
+@pytest.fixture
+def submission():
+    return Submission(copy_number=0)
+
+
+@pytest.fixture
+def solution():
+    return Solution()
+
+
+@pytest.fixture
+def scan():
+    return Scan(name='', status='')
+
+
+@pytest.fixture
+def page():
+    return Page(path='', number=0)
+
+
+@pytest.fixture
+def feedback_option():
+    return FeedbackOption(text='')

zesje/api/exams.py

@@ -42,19 +42,7 @@ class Exams(Resource):
         elif Submission.query.filter(Submission.exam_id == exam.id).count():
             return dict(status=500, message='Exam is not finalized but already has submissions.'), 500
         else:
-            # Delete any scans that were wrongly uploaded to this exam
-            for scan in exam.scans:
-                db.session.delete(scan)
-
-            for widget in exam.widgets:
-                db.session.delete(widget)
-
-            for problem in exam.problems:
-                for fb_option in problem.feedback_options:
-                    db.session.delete(fb_option)
-                db.session.delete(problem.widget)
-                db.session.delete(problem)
-
+            # All corresponding solutions, scans and problems are automatically deleted
             db.session.delete(exam)
             db.session.commit()
 

zesje/api/problems.py

@@ -105,10 +105,7 @@ class Problems(Resource):
         if any([sol.graded_by is not None for sol in problem.solutions]):
             return dict(status=403, message=f'Problem has already been graded'), 403
         else:
-            # Delete all solutions associated with this problem
-            for sol in problem.solutions:
-                db.session.delete(sol)
-            db.session.delete(problem.widget)
+            # The widget and all associated solutions are automatically deleted
             db.session.delete(problem)
             db.session.commit()
             return dict(status=200, message="ok"), 200

zesje/database.py

@@ -62,10 +62,11 @@ class Exam(db.Model):
     id = Column(Integer, primary_key=True, autoincrement=True)
     name = Column(Text, nullable=False)
     token = Column(String(token_length), unique=True, default=_generate_exam_token)
-    submissions = db.relationship('Submission', backref='exam', lazy=True)
-    problems = db.relationship('Problem', backref='exam', order_by='Problem.id', lazy=True)
-    scans = db.relationship('Scan', backref='exam', lazy=True)
-    widgets = db.relationship('ExamWidget', backref='exam', order_by='ExamWidget.id', lazy=True)
+    submissions = db.relationship('Submission', backref='exam', cascade='all', lazy=True)
+    problems = db.relationship('Problem', backref='exam', cascade='all', order_by='Problem.id', lazy=True)
+    scans = db.relationship('Scan', backref='exam', cascade='all', lazy=True)
+    widgets = db.relationship('ExamWidget', backref='exam', cascade='all',
+                              order_by='ExamWidget.id', lazy=True)
     finalized = Column(Boolean, default=False, server_default='f')
 
 
@@ -75,8 +76,9 @@ class Submission(db.Model):
     id = Column(Integer, primary_key=True, autoincrement=True)
     copy_number = Column(Integer, nullable=False)
     exam_id = Column(Integer, ForeignKey('exam.id'), nullable=False)
-    solutions = db.relationship('Solution', backref='submission', order_by='Solution.problem_id', lazy=True)
-    pages = db.relationship('Page', backref='submission', lazy=True)
+    solutions = db.relationship('Solution', backref='submission', cascade='all',
+                                order_by='Solution.problem_id', lazy=True)
+    pages = db.relationship('Page', backref='submission', cascade='all', lazy=True)
     student_id = Column(Integer, ForeignKey('student.id'), nullable=True)
     signature_validated = Column(Boolean, default=False, server_default='f', nullable=False)
 
@@ -96,9 +98,10 @@ class Problem(db.Model):
     id = Column(Integer, primary_key=True, autoincrement=True)
     name = Column(Text, nullable=False)
     exam_id = Column(Integer, ForeignKey('exam.id'), nullable=False)
-    feedback_options = db.relationship('FeedbackOption', backref='problem', order_by='FeedbackOption.id', lazy=True)
-    solutions = db.relationship('Solution', backref='problem', lazy=True)
-    widget = db.relationship('ProblemWidget', backref='problem', uselist=False, lazy=True)
+    feedback_options = db.relationship('FeedbackOption', backref='problem', cascade='all',
+                                       order_by='FeedbackOption.id', lazy=True)
+    solutions = db.relationship('Solution', backref='problem', cascade='all', lazy=True)
+    widget = db.relationship('ProblemWidget', backref='problem', cascade='all', uselist=False, lazy=True)
 
 
 class FeedbackOption(db.Model):