#29178: Mutable default in `Index` constructor
-------------------------------------+-------------------------------------
Reporter: Flavio | Owner: nobody
Curella |
Type: | Status: new
Cleanup/optimization |
Component: Database | Version: master
layer (models, ORM) |
Severity: Normal | Keywords:
Triage Stage: | Has patch: 0
Unreviewed |
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 1
UI/UX: 0 |
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the {{{__init__}}} method of the {{{Index}}} class has the following
signature
(https://github.com/django/django/blob/master/django/db/models/indexes.py#L15):
{{{
def __init__(self, *, fields=[], name=None, db_tablespace=None):
}}}
The {{{fields}}} argument is set to a mutable object, which is usually
considered bad practice as it can lead to unexpected results:
* http://effbot.org/zone/default-values.htm
* http://docs.python-guide.org/en/latest/writing/gotchas/
There are some valid uses of mutable defaults, but I can't see any code
taking advantage of the mutability by looking at the code of the
{{{Index}}} class.
If there's no good reason for the default to be mutable, it should be
changed to:
{{{
def __init__(self, *, fields=None, name=None, db_tablespace=None):
if fields is None:
fields = []
# ...rest of the code
}}}
If there's a good reason, I think we should document it in a comment.
--
Ticket URL: <https://code.djangoproject.com/ticket/29178>
Django <https://code.djangoproject.com/>
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