dbshell crashes on Postgres backend with empty database name

[Ilya Semenov]

Django database backend postgresql_psycopg2 works perfectly fine without specifying database NAME (falling back to the user name for the database name) until you run manage.py dbshell, when it crashes.

Please see the test case below.

root@3a46382913a8:/# /app/src/manage.py shell
>>> from django.conf import settings
>>> pprint(settings.DATABASES['default'])
{'ATOMIC_REQUESTS': False,
 'AUTOCOMMIT': True,
 'CONN_MAX_AGE': 0,
 'ENGINE': 'django.db.backends.postgresql_psycopg2',
 'HOST': '172.17.0.3',
 'NAME': None,
 'OPTIONS': {},
 'PASSWORD': 'xxx',
 'PORT': '5432',
 'TEST': {'CHARSET': None, 'COLLATION': None, 'MIRROR': None, 'NAME': None},
 'TIME_ZONE': None,
 'USER': 'postgres'}
>>> from django.db import connection
>>> c=connection.cursor(); c.execute("SELECT 1"); print(c.fetchone())
(1,)

but:

root@3a46382913a8:/# /app/src/manage.py dbshell
Traceback (most recent call last):
  File "/app/src/manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "/usr/local/lib/python3.5/dist-packages/django/core/management/__init__.py", line 353, in execute_from_command_line
    utility.execute()
  File "/usr/local/lib/python3.5/dist-packages/django/core/management/__init__.py", line 345, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 348, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/usr/local/lib/python3.5/dist-packages/django/core/management/base.py", line 399, in execute
    output = self.handle(*args, **options)
  File "/usr/local/lib/python3.5/dist-packages/django/core/management/commands/dbshell.py", line 19, in handle
    connection.client.runshell()
  File "/usr/local/lib/python3.5/dist-packages/django/db/backends/postgresql/client.py", line 66, in runshell
    DatabaseClient.runshell_db(self.connection.settings_dict)
  File "/usr/local/lib/python3.5/dist-packages/django/db/backends/postgresql/client.py", line 46, in runshell_db
    _escape_pgpass(name) or '*',
  File "/usr/local/lib/python3.5/dist-packages/django/db/backends/postgresql/client.py", line 13, in _escape_pgpass
    return txt.replace('\\', '\\\\').replace(':', '\\:')
AttributeError: 'NoneType' object has no attribute 'replace'

[Claude Paroz]

Most probably a regression in 1.9 introduced by b64c0d4d613b5cabedbc9b847682fe14877537de

[mieciu]

It's something related to postgresql's DatabaseClient class and temporary .pgpass file creation.

IMO omitting such a vital parameter database name is a crucial mistake in configuration and nobody should rely here on any fallback mechanism...

[Claude Paroz]

If we want Django refusing the default database name with Postgres, that should be the subject of a separate ticket (and maybe a discussion on the django-developers mailing list). But clearly, the _escape_pgpass should not crash when receiving a None value.

[mieciu]

I totally agree.

However, I've found a way to actually have the fallback mechanism working for dbshell, so at least we're consistent here :)

PR is already waiting.

[Philip James]

Should a test be added to account for the case where 'NAME' == None?

[Tim Graham]

I don't see an easy way to add a regression test for this since the current tests bypass DatabaseClient.runshell() which is what's changed to fix the issue.

[Tim Graham <timograham@…>]

In 19ff5068:

Fixed #26698 -- Fixed PostgreSQL dbshell crash on an empty database name.

[Tim Graham <timograham@…>]

In 9a204fc:

[1.10.x] Fixed #26698 -- Fixed PostgreSQL dbshell crash on an empty database name.

Backport of 19ff506878071ac93de684fe01328707e75e2b3a from master

[Tim Graham <timograham@…>]

In 5d60eb8b:

[1.9.x] Fixed #26698 -- Fixed PostgreSQL dbshell crash on an empty database name.

Backport of 19ff506878071ac93de684fe01328707e75e2b3a from master