Python flask and custom client error messages

Question

I'm currently writing a REST API for an app I'm working on. The app is written in python using flask. I have the following:

try:
    _profile = profile(
        name=request.json['name'],
        password=profile.get_salted_password('blablabla'),
        email=request.json['email'],
        created_by=1,
        last_updated_by=1
    )
except AssertionError:
    abort(400)

session = DatabaseEngine.getSession()
session.add(_profile)
try:
    session.commit()
except IntegrityError:
    abort(400)

The error handler looks like this:

@app.errorhandler(400)
def not_found(error):
    return make_response(standard_response(None, 400, 'Bad request'), 400)

I'm using the error 400 to denote both a problem with a sqlalchemy model validator and a unique constraint when writing to the database and in both cases the following error is sent to the client:

{
  "data": null,
  "error": {
    "msg": "Bad request",
    "no": 400
  },
  "success": false
}

Is there a way to still use abort(400) but also set the error somehow so that the error handler can take care of adding additional information for the error object in the result?

I would like it to be more in line with:

{
  "data": null,
  "error": {
    "msg": "(IntegrityError) duplicate key value violates unique constraint profile_email_key",
    "no": 400
  },
  "success": false
}

codegeek · Accepted Answer · 2013-08-06 14:33:41Z

9

you can directly put a custom response in abort() function:

abort(make_response("Integrity Error", 400))

Alternatively, you can put it in the error handler function

@app.errorhandler(400)
def not_found(error):
resp = make_response("Integrity Error", 400)
return resp

edited Aug 6, 2013 at 14:33

answered Aug 6, 2013 at 14:05

codegeek

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3 Comments

Asken Over a year ago

It works to produce the output but it seems like the error 400 handler is not being called if I do this. Is there a way to still end up there since I was planning on doing some logging in the error handlers?

Asken Over a year ago

Yeah, that won't work since then I'm back where I started where all 400 will be Integrity Error instead of Bad Request. I need to make both custom error text and end up in the error handler. :)

Curtis Yallop Over a year ago

abort does not take a response in the current api. flask.pocoo.org/docs/api

Sean Vieira · Accepted Answer · 2013-10-18 01:33:33Z

8

errorhandler can take an exception type as well:

@app.errorhandler(AssertionError)
def handle_sqlalchemy_assertion_error(err):
    return make_response(standard_response(None, 400, err.message), 400)

edited Oct 18, 2013 at 1:33

answered Aug 6, 2013 at 16:37

Sean Vieira

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2 Comments

Asken Over a year ago

Yup, this was the one I was looking for. Is there a way to catch errors not bound to a handler like a "catch-all" so I can format and handle that to the client too?

Curtis Yallop Over a year ago

That make_response and standard_response doesn't work for me. But this does: "def handle_sqlalchemy_error(err): return err.message, 400"

haferje · Accepted Answer · 2014-04-08 02:50:53Z

0

i know am late to the game, but for anyone who wants another solution, mine is based on the answer by @codegeek.

i was able to accomplish something similar with the following in my ServerResponse.py module:

def duplicate(message=""):
    response = make_response()
    response.status_code = 409
    response.headers = {
        "X-Status-Reason" : message or "Duplicate entry"
    }
    abort(response)

then i can call

ServerResponse.duplicate('Duplicate submission. An article with a similar title already exists.')

this makes it easy in my AngularJS app to check for a response status and display the X-Status-Reason default or customized message

edited Apr 8, 2014 at 2:50

answered Apr 8, 2014 at 2:43

haferje

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