get_or_create should preserve the original traceback.

[Dougal Matthews]

(more context in #15117)

get_or_create in django.db.models.query re-raises the last exception as below. This modifies the traceback and the exception should preserve this.

            except IntegrityError, e:
                transaction.savepoint_rollback(sid, using=self.db)
                try:
                    return self.get(**lookup), False
                except self.model.DoesNotExist:
                    raise e

this can be fixed with

                exc_info = sys.exc_info()
                try:
                    return self.get(**lookup), False
                except self.model.DoesNotExist:
                    raise exc_info[1], None, exc_info[2]

[Dougal Matthews]

Added a patch that preserves the original traceback with a test. The test isn't ideal since we need to check the contents of a traceback, but it looks for the save call since this is where the IntegrityError comes from (in other words its the safest thing we can bet on being there.)

[Dougal Matthews]

For reference. This patch changes a traceback like this:

Traceback (most recent call last):
  File "/vagrant/tests/modeltests/get_or_create/tests.py", line 60, in test_get_or_create
    ManualPrimaryKeyTest.objects.get_or_create(id=1, data="Different")
  File "/vagrant/django/db/models/manager.py", line 135, in get_or_create
    return self.get_query_set().get_or_create(**kwargs)
  File "/vagrant/django/db/models/query.py", line 396, in get_or_create
    raise e
IntegrityError: PRIMARY KEY must be unique

to show the original full exception traceback:

Traceback (most recent call last):
  File "/vagrant/tests/modeltests/get_or_create/tests.py", line 60, in test_get_or_create
    ManualPrimaryKeyTest.objects.get_or_create(id=1, data="Different")
  File "/vagrant/django/db/models/manager.py", line 135, in get_or_create
    return self.get_query_set().get_or_create(**kwargs)
  File "/vagrant/django/db/models/query.py", line 386, in get_or_create
    obj.save(force_insert=True, using=self.db)
  File "/vagrant/django/db/models/base.py", line 463, in save
    self.save_base(using=using, force_insert=force_insert, force_update=force_update)
  File "/vagrant/django/db/models/base.py", line 556, in save_base
    result = manager._insert(values, return_id=update_pk, using=using)
  File "/vagrant/django/db/models/manager.py", line 198, in _insert
    return insert_query(self.model, values, **kwargs)
  File "/vagrant/django/db/models/query.py", line 1459, in insert_query
    return query.get_compiler(using=using).execute_sql(return_id)
  File "/vagrant/django/db/models/sql/compiler.py", line 810, in execute_sql
    cursor = super(SQLInsertCompiler, self).execute_sql(None)
  File "/vagrant/django/db/models/sql/compiler.py", line 754, in execute_sql
    cursor.execute(sql, params)
  File "/vagrant/django/db/backends/sqlite3/base.py", line 226, in execute
    return Database.Cursor.execute(self, query, params)
IntegrityError: PRIMARY KEY must be unique

[Jonas Obrist]

Updated the patch to apply to trunk.

Also made use of the new unittest2 features (namely assertIn).

​https://github.com/ojii/django/compare/django:master...ojii:16340

[Jonas Obrist]

new patch (same as ​https://github.com/ojii/django/compare/django:master...ojii:16340)

[Julien Phalip]

In [17333]:

Fixed #16340 -- Made get_or_create() re-raise any IntegrityError with its original traceback. Thanks to d0ugal and Jonas Obrist.