Exception handling for database queries

ref-test/app/tools/auth.py

@@ -1,18 +1,23 @@
 from .data import load
 from ..models import User
+from ..tools.logs import write
 
-from flask import abort, redirect
-from flask.helpers import flash, url_for
+from flask.helpers import abort, flash, redirect, url_for
 from flask_login import current_user
+from sqlalchemy.exc import SQLAlchemyError
 
 from functools import wraps
 
 def require_account_creation(function):
     @wraps(function)
     def wrapper(*args, **kwargs):
-        if User.query.count() == 0:
-            flash('Please register a user account.', 'alert')
-            return redirect(url_for('admin._register'))
+        try:
+            if User.query.count() == 0:
+                flash('Please register a user account.', 'alert')
+                return redirect(url_for('admin._register'))
+        except SQLAlchemyError as exception:
+            write('system.log', f'Database error when checking for existing accounts: {exception}')
+            return abort(500)
         return function(*args, **kwargs)
     return wrapper
 

ref-test/app/tools/data.py

@@ -1,8 +1,9 @@
 from ..models import Dataset
+from ..tools.logs import write
 
 from flask import current_app as app
-from flask import flash, redirect
-from flask.helpers import url_for
+from flask.helpers import abort, flash, redirect, url_for
+from sqlalchemy.exc import SQLAlchemyError
 
 import json
 from pathlib import Path
@@ -76,7 +77,10 @@ def get_tag_list(dataset:list):
 def check_dataset_exists(function):
     @wraps(function)
     def wrapper(*args, **kwargs):
-        datasets = Dataset.query.all()
+        try: datasets = Dataset.query.all()
+        except SQLAlchemyError as exception:
+            write('system.log', f'Database error when checking existing datasets: {exception}')
+            return abort(500)
         if not datasets:
             flash('There are no available question datasets. Please upload a question dataset first, or use the question editor to create a new dataset.', 'error')
             return redirect(url_for('admin._questions'))

ref-test/app/tools/forms.py

@@ -1,7 +1,9 @@
 
 from ..extensions import db
+from ..tools.logs import write
 
 from flask import jsonify
+from sqlalchemy.exc import SQLAlchemyError
 from wtforms.validators import ValidationError
 
 import json
@@ -47,7 +49,10 @@ def get_time_options():
 
 def get_dataset_choices():
     from ..models import Dataset
-    datasets = Dataset.query.all()
+    try: datasets = Dataset.query.all()
+    except SQLAlchemyError as exception:
+        write('system.log', f'Database error when fetching dataset lists: {exception}')
+        return []
     dataset_choices = []
     for dataset in datasets:
         label = dataset.get_name()

ref-test/app/tools/test.py

@@ -1,8 +1,10 @@
 from .data import randomise_list
 from ..models import Entry
+from ..tools.logs import write
 
-from flask import redirect, request, session
-from flask.helpers import url_for
+from flask import request, session
+from flask.helpers import abort, redirect, url_for
+from sqlalchemy.exc import SQLAlchemyError
 
 from functools import wraps
 
@@ -129,8 +131,11 @@ def redirect_if_started(function):
     @wraps(function)
     def wrapper(*args, **kwargs):
         id = session.get('id')
-        if request.method == 'GET' and id and Entry.query.filter_by(id=id).first():
-            return redirect(url_for('quiz._quiz'))
+        try:
+            if request.method == 'GET' and id and Entry.query.filter_by(id=id).first(): return redirect(url_for('quiz._quiz'))
+        except SQLAlchemyError as exception:
+            write('system.log', f'Database error when checking if test has been started: {exception}')
+            return abort(500)
         return function(*args, **kwargs)
     return wrapper