id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
26540	"Can't run tests without ""default"" connection set"	Marcin Nowak	nobody	"According to use cases described in #19775 and #16752 I'm using project with explicit db routing and no ""default"" connection.  

When I'm trying to run tests with empty 'default' connection, I'm getting:

{{{
Traceback (most recent call last):
  File ""/home/marcin/myproject/eggs/Django-1.8.6-py2.7.egg/django/test/testcases.py"", line 946, in setUpClass
    if not connections_support_transactions():
  File ""/home/marcin/myproject/eggs/Django-1.8.6-py2.7.egg/django/test/testcases.py"", line 911, in connections_support_transactions
    for conn in connections.all())
  File ""/home/marcin/myproject/eggs/Django-1.8.6-py2.7.egg/django/test/testcases.py"", line 911, in <genexpr>
    for conn in connections.all())
  File ""/home/marcin/myproject/eggs/Django-1.8.6-py2.7.egg/django/utils/functional.py"", line 59, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File ""/home/marcin/myproject/eggs/Django-1.8.6-py2.7.egg/django/db/backends/base/features.py"", line 216, in supports_transactions
    with self.connection.cursor() as cursor:
  File ""/home/marcin/myproject/eggs/Django-1.8.6-py2.7.egg/django/db/backends/base/base.py"", line 164, in cursor
    cursor = self.make_cursor(self._cursor())
  File ""/home/marcin/myproject/eggs/Django-1.8.6-py2.7.egg/django/db/backends/dummy/base.py"", line 21, in complain
    raise ImproperlyConfigured(""settings.DATABASES is improperly configured. ""
ImproperlyConfigured: settings.DATABASES is improperly configured. Please supply the ENGINE value. Check settings documentation for more details.

}}}

When running without ""default"" key configured, I'm getting an error probably on the first attempt to get specific connection (not the ""default"" one):

{{{
[...]
  File ""/home/marcin/myproject/etl/analysis/etltoolkit.py"", line 1098, in dimension_factory
    sequencer = sequencer or SurrogateKeySequencer(dwhmodel)
  File ""/home/marcin/myproject/etl/analysis/etltoolkit.py"", line 739, in __init__
    self.connection = connection or connections['etlstg']
  File ""/home/marcin/myproject/eggs/Django-1.8.6-py2.7.egg/django/db/utils.py"", line 237, in __getitem__
    self.ensure_defaults(alias)
  File ""/home/marcin/myproject/eggs/Django-1.8.6-py2.7.egg/django/db/utils.py"", line 168, in ensure_defaults
    conn = self.databases[alias]
  File ""/home/marcin/myproject/eggs/Django-1.8.6-py2.7.egg/django/utils/functional.py"", line 59, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File ""/home/marcin/myproject/eggs/Django-1.8.6-py2.7.egg/django/db/utils.py"", line 159, in databases
    raise ImproperlyConfigured(""You must define a '%s' database"" % DEFAULT_DB_ALIAS)
django.core.exceptions.ImproperlyConfigured: You must define a 'default' database
}}} 

The bug lies in `ConnectionHandler.databases()`:

{{{
    def databases(self):
        if self._databases is None:
            self._databases = settings.DATABASES
        if self._databases == {}:
            self._databases = {
                DEFAULT_DB_ALIAS: {
                    'ENGINE': 'django.db.backends.dummy',
                },
            }
        if DEFAULT_DB_ALIAS not in self._databases:
            raise ImproperlyConfigured(""You must define a '%s' database"" % DEFAULT_DB_ALIAS)
        return self._databases
}}}

When `ensure_defaults()` asks for specified connection (in my case - ""etlstg"" alias), the `databases()` is called as a property getter  and checks existence of DEFAULT_DB_ALIAS.

Please do not force us to use DEFAULT_DB_ALIAS if you won't allow to rename it in settings (#26197).

"	Bug	closed	Database layer (models, ORM)	1.8	Normal	duplicate			Unreviewed	0	0	0	0	0	0