Exception handling for database commit operations

ref-test/app/models/test.py

@@ -3,6 +3,7 @@ from ..tools.forms import JsonEncodedDict
 from ..tools.logs import write
 
 from flask_login import current_user
+from sqlalchemy.exc import SQLAlchemyError
 
 from datetime import date, datetime
 import secrets
@@ -52,15 +53,25 @@ class Test(db.Model):
             errors.append('The expiry date cannot be before the start date.')
         if errors:
             return False, errors
-        db.session.add(self)
-        db.session.commit()
+        try:
+            db.session.add(self)
+            db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when creating test {self.get_code()}: {exception}')
+            return False, f'Database error: {exception}'
         write('system.log', f'Test with code {self.get_code()} created by {current_user.get_username()}.')
         return True, f'Test with code {self.get_code()} has been created.'
     
     def delete(self):
         if self.entries: return False, f'Cannot delete a test with submitted entries.'
         db.session.delete(self)
-        db.session.commit()
+        try:
+            db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when deleting test {self.get_code()}: {exception}')
+            return False, f'Database error: {exception}'
         write('system.log', f'Test with code {self.get_code()} has been deleted by {current_user.get_username()}.')
         return True, f'Test with code {self.get_code()} has been deleted.'
     
@@ -68,7 +79,12 @@ class Test(db.Model):
         now = datetime.now()
         if self.start_date.date() > now.date():
             self.start_date = now
-            db.session.commit()
+            try:
+                db.session.commit()
+            except SQLAlchemyError as exception:
+                db.session.rollback()
+                write('system.log', f'Database error when launching test {self.get_code()}: {exception}')
+                return False, f'Database error: {exception}'
             write('system.log', f'Test with code {self.get_code()} has been started by {current_user.get_username()}.')
             return True,  f'Test with code {self.get_code()} has been started.'
         return False, f'Test with code {self.get_code()} has already started.'
@@ -77,7 +93,12 @@ class Test(db.Model):
         now = datetime.now()
         if self.end_date >= now:
             self.end_date = now
-            db.session.commit()
+            try:
+                db.session.commit()
+            except SQLAlchemyError as exception:
+                db.session.rollback()
+                write('system.log', f'Database error when closing test {self.get_code()}: {exception}')
+                return False, f'Database error: {exception}'
             write('system.log', f'Test with code {self.get_code()} ended by {current_user.get_username()}.')
             return True, f'Test with code {self.get_code()} has been ended.'
         return False, f'Test with code {self.get_code()} has already ended.'
@@ -87,7 +108,12 @@ class Test(db.Model):
         code = secrets.token_hex(3).lower()
         adjustments[code] = time
         self.adjustments = adjustments
-        db.session.commit()
+        try:
+            db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when adding adjustment to test {self.get_code()}: {exception}')
+            return False, f'Database error: {exception}'
         write('system.log', f'Time adjustment for {time} minutes with code {code} added to test {self.get_code()} by {current_user.get_username()}.')
         return True, f'Time adjustment for {time} minutes added to test {self.get_code()}. This can be accessed using the user code {code.upper()}.'
 
@@ -95,7 +121,12 @@ class Test(db.Model):
         if not self.adjustments: return False, f'There are no adjustments configured for test {self.get_code()}.'
         self.adjustments.pop(code)
         if not self.adjustments: self.adjustments = None
-        db.session.commit()
+        try:
+            db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when deleting adjustment from test {self.get_code()}: {exception}')
+            return False, f'Database error: {exception}'
         write('system.log', f'Time adjustment for with code {code} has been removed from test {self.get_code()} by {current_user.get_username()}.')
         return True, f'Time adjustment for with code {code} has been removed from test {self.get_code()}.'
 
@@ -104,6 +135,11 @@ class Test(db.Model):
         if start_date: self.start_date = start_date
         if end_date: self.end_date = end_date
         if time_limit is not None: self.time_limit = time_limit
-        db.session.commit()
+        try:
+            db.session.commit()
+        except SQLAlchemyError as exception:
+            db.session.rollback()
+            write('system.log', f'Database error when updating test {self.get_code()}: {exception}')
+            return False, f'Database error: {exception}'
         write('system.log', f'Test with code {self.get_code()} has been updated by user {current_user.get_username()}.')
         return True, f'Test with code {self.get_code()} has been updated by.'