Inconsistent exception raising on DB integrity errors

[Ramiro Morales]

It seems we aren't capturing the <db api driver module>.IntegrityError exceptions raised when connection.commit() is executed in the same way we do in execute().

Found this while creating tests to verify FK constraint in sqlite (#14204). My assertRaises(django.db.[utils.]IntegrityError, ...) weren't being triggered and printing the exception type shows <class 'pysqlite2.dbapi2.IntegrityError'>. Same thing happens now with postgres (see below).

The DatabaseError and IntegrityError unification was introduced in r12352, if this is confirmed as an issue it wouldn't be a regression in 1.2, but a 1.2 feature introduced in an incomplete fashion.

The two files pasted at the end form a small test case. When run under postgres you see:

======================================================================
ERROR: Try to create a model instance that violates a FK constraint. Should fail
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/r/django/sqlite_fk2/tests/regressiontests/fk_constraints/tests.py", line 22, in test_integrity_checks_on_creation
    a.save()
  File "/home/r/django/sqlite_fk2/django/db/models/base.py", line 434, in save
    self.save_base(using=using, force_insert=force_insert, force_update=force_update)
  File "/home/r/django/sqlite_fk2/django/db/models/base.py", line 534, in save_base
    transaction.commit_unless_managed(using=using)
  File "/home/r/django/sqlite_fk2/django/db/transaction.py", line 175, in commit_unless_managed
    connection._commit()
  File "/home/r/django/sqlite_fk2/django/db/backends/__init__.py", line 32, in _commit
    return self.connection.commit()
IntegrityError: insert or update on table "fk_constraints_article" violates foreign key constraint "fk_constraints_article_reporter_id_fkey"
DETAIL:  Key (reporter_id)=(30) is not present in table "fk_constraints_reporter".

<class 'psycopg2.IntegrityError'>

# models.py
from django.db import models

class Reporter(models.Model):
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=30)
    email = models.EmailField()

    def __unicode__(self):
        return u"%s %s" % (self.first_name, self.last_name)

class Article(models.Model):
    headline = models.CharField(max_length=100)
    pub_date = models.DateField()
    reporter = models.ForeignKey(Reporter)

    def __unicode__(self):
        return self.headline

    class Meta:
        ordering = ('headline',)

# tests.py
from datetime import datetime

from django.db import utils
from django.test import TransactionTestCase

from models import Reporter, Article

import sys

class FkConstraintsTest(TransactionTestCase):

    def setUp(self):
        # Create a Reporter.
        self.r = Reporter.objects.create(first_name='John', last_name='Smith', email='john@example.com')
        #self.r2 = Reporterobjects.create(first_name='Paul', last_name='Jones', email='paul@example.com')

    def test_integrity_checks_on_creation(self):
        """Try to create a model instance that violates a FK constraint. Should fail"""
        a = Article(headline="This is a test", pub_date=datetime(2005, 7, 27), reporter_id=30)
        #self.assertRaises(utils.IntegrityError, a.save)
        try:
            a.save()
        except Exception, e:
            print >>sys.stderr, type(e)
            raise

    def test_integrity_checks_on_update(self):
        """Try to update a model instance introducing a FK constraint violation. Should fail"""
        # Create an Article.
        Article.objects.create(headline="Test article", pub_date=datetime(2010, 9, 4), reporter=self.r)
        # Retrive it from the DB
        a = Article.objects.get(headline="Test article")
        a.reporter_id = 30
        #self.assertRaises(utils.IntegrityError, a.save)
        try:
            a.save()
        except Exception, e:
            print >>sys.stderr, type(e)
            raise

[Alex Gaynor]

IMO we should capture and convert ALWAYS, it just seems like the sane thing to do.

[Ramiro Morales]

Patch for this issue, includes tests

[Ramiro Morales]

Enhanced patch, check for django.db.IntegrityError instead of django.db.utils IntegrityError in the tests, added a comment