python - How to return "already exists" error in Flask-restless? -

i handler exception. i'm using combination of flask-restless , sqlalchemy in python.

my problem:

when send request api object exists in db, sqlalchemy shows exception:

integrityerror: (integrityerror) column <column_name> not unique u'insert ... 

so have tried add attribute validation_exceptions create_api method:

manager.create_api( ... , validation_exceptions=[integrityerror]) 

but response json contains:

{     "validation_errors": "could not determine specific validation errors" }  

and server api shows exception :

traceback (most recent call last):   file "c:\python27\lib\site-packages\flask_restless\views.py", line 797, in _extract_error_messages     left, right = str(exception).rsplit(':', 1) valueerror: need more 1 value unpack 

exception validation in flask-restless doesn't work type of exception (integrityerror)

what should do? possible create handler exception , return own error message in json?

the documentation (v0.17.0 date of posting) states:

currently, flask-restless expects instance of specified validation error have errors attribute, dictionary mapping field name error description (note: 1 error per field).

so change content of validation_errors exception needs errors attribute contains dictionary. content of dictionary appear in servers response validation_errors.

from flask-restless/tests/test_validation.py:

class testsimplevalidation(managertestbase): """tests validation errors raised sqlalchemy's simple built-in validation. more information functionality, see documentation :func:`sqlalchemy.orm.validates`. """  def setup(self):     """create apis validated models."""     super(testsimplevalidation, self).setup()      class person(self.base):         __tablename__ = 'person'         id = column(integer, primary_key=true)         age = column(integer, nullable=false)          @validates('age')         def validate_age(self, key, number):             if not 0 <= number <= 150:                 exception = coolvalidationerror()                 exception.errors = dict(age='must between 0 , 150')                 raise exception             return number          @validates('articles')         def validate_articles(self, key, article):             if article.title not none , len(article.title) == 0:                 exception = coolvalidationerror()                 exception.errors = {'articles': 'empty title not allowed'}                 raise exception             return article      class article(self.base):         __tablename__ = 'article'         id = column(integer, primary_key=true)         title = column(unicode)         author_id = column(integer, foreignkey('person.id'))         author = relationship('person', backref=backref('articles'))      self.article = article     self.person = person     self.base.metadata.create_all()     self.manager.create_api(article)     self.manager.create_api(person, methods=['post', 'patch'],                             validation_exceptions=[coolvalidationerror]) 

request:

data = dict(data=dict(type='person', age=-1)) response = self.app.post('/api/person', data=dumps(data)) 

response:

http/1.1 400 bad request  { "validation_errors":     {       "age": "must between 0 , 150",     } }