# Creating failing webuser from flask still adds the user
**URL:** https://discuss.tryton.org/t/creating-failing-webuser-from-flask-still-adds-the-user/5275
**Category:** Developer
**Tags:** web-user, flask
**Created:** [May 18, 2022, 9:37pm UTC](https://discuss.tryton.org/t/creating-failing-webuser-from-flask-still-adds-the-user/5275 "2022-05-18T21:37:56Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@edbo](https://discuss.tryton.org/u/edbo)
#### Post date: [May 18, 2022, 9:37pm UTC](https://discuss.tryton.org/t/creating-failing-webuser-from-flask-still-adds-the-user/5275/1 "2022-05-18T21:37:56Z")
Using the `web_user` module, the email address has a SQL constraint to be unique. When adding a new web user from the desktop client with an email address already in the database it will fail and no new user is created. This is the right behavior.
Now I want to do the same from my webapp. The app sends an email address and password in JSON format to the backend which is Flask with the flask-tryton package. The backend then calls the `create` function on `web.user` to create the user. When using an email address which is already in the database I get an error back which is expected.
What is not expected, is that even an error is returned, the user is still created in the database.
My code:
```python
app.config['TRYTON_USER'] = 2 # normal user
WebUser = tryton.pool.get('web.user')
@app.route('/register_email', methods=['POST'])
@tryton.transaction()
def register_email():
data = request.get_json()
res = {}
if 'username' and 'password' in data:
try:
user = WebUser.create([{
'email': data['username'],
'password': data['password']
}])
res['result'] = []
except Exception as e:
# return error. This can be about unique email addresses
res['error'] = {'error': "{0}".format(str(e))}
else:
res['error'] = {'error': 'Wrong data entered.'}
return json.dumps(res)
```
So I get the error “`E-mail of active web user must be unique.`” back, but the user is still created in the database.
Python 3.9.6, flask-tryton 0.11.0 and trytond 6.4.0 with a sqlite database (will that be a problem?)
Do I need some extra checks to overcome this problem?
---
### Author:  [@ced](https://discuss.tryton.org/u/ced)
#### Post date: [May 18, 2022, 9:49pm UTC](https://discuss.tryton.org/t/creating-failing-webuser-from-flask-still-adds-the-user/5275/2 "2022-05-18T21:49:53Z")
If you do not raise an exception, `transaction` decorator does not know that it has to rollback the transaction.
The best is to use the `abort` function from Flask.
---
### Author:  [@edbo](https://discuss.tryton.org/u/edbo)
#### Post date: [May 18, 2022, 9:58pm UTC](https://discuss.tryton.org/t/creating-failing-webuser-from-flask-still-adds-the-user/5275/3 "2022-05-18T21:58:41Z")
Indeed, adding `abort` fixes this.
```python
try:
# ......
except Exception as e:
# return error. This can be about unique email addresses
res['error'] = {'error': "{0}".format(str(e))}
abort(400, json.dumps(res))
```
---
### Author:  [@system](https://discuss.tryton.org/u/system)
#### Post date: [June 17, 2022, 9:59pm UTC](https://discuss.tryton.org/t/creating-failing-webuser-from-flask-still-adds-the-user/5275/4 "2022-06-17T21:59:29Z")
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