Model field relational attributes are None by default, not False

[Markus Holtermann]

The docs state that the relational attributes, such as many_to_many, one_to_many, etc should be False by default (​https://docs.djangoproject.com/en/1.8/ref/models/fields/#attributes-for-fields-with-relations). In practice they are None though.

According to Daniel on IRC they should be False not None (i.e. the documentation is correct).

[pirosb3]

yoongkang, are you doing this?

[Yoong Kang Lim]

pirosb3, sorry I think I must have mixed this up with a different issue. How do I assign it back to you?

[honya121]

It seems that the relational attributes are None only for non-relational fields (Field.is_relation=False). For relational fields these attributes are False or True. This is right behaviour according to the documentation (the values should only be meaningful if Field.is_relation=True), but it is possible, that I tested it badly. So there are 2 options:
a) keep default relational values in the non-relational fields None
b) set default relational values for ALL fields to False

For both options, it would be good to write what values are default even for fields with Field.is_relation=False, instead of writing that these fields will have unmeaningful values.

[Markus Holtermann]

Hi honya121, in my opinion you should go forward with option b. I don't understand what you mean with your last sentence.

[honya121]

Hi, ok, I'll do the b) option. The last sentence is about documentation. Sorry, I forgot to mention that. Anyway, in the documentation, there should be also mentioned, that the relational attributes will be False for non-relational fields.

[Tim Graham]

​PR

[Tim Graham]

I'd like to better understand the rationale for this change. In my mind, None for non-relational fields seems like it may make debugging easier, e.g. if you find a None value, then you'll know you forgot to check is_relation.

[Carl Meyer]

I agree with timgraham. It seems entirely sensible to me to have the relation-cardinality attributes be None (as in, neither True nor False because they are not even applicable in the first place) for non-relational fields. I don't see the rationale for changing them to False.

[Markus Holtermann]

Either way makes sense in my eyes. E.g. "Am I a one_to_many field?" -- "No" --> False. In that case I think we still need to update the docs.

[Tim Graham]

docs/ref/models/fields.txt

@@ -1883 +1883 @@
 
 These attributes are used to query for the cardinality and other details of a
 relation. These attribute are present on all fields; however, they will only
-have meaningful values if the field is a relation type
+have boolean values (rather than ``None``) if the field is a relation type
 (:attr:`Field.is_relation=True <Field.is_relation>`).
 
 .. attribute:: Field.many_to_many

[Tim Graham <timograham@…>]

In 2b08622:

Fixed #24665 -- Clarified model field flag defaults.

[Tim Graham <timograham@…>]

In afae8ff:

[1.8.x] Fixed #24665 -- Clarified model field flag defaults.

Backport of 2b086229a2a6c786e32da37b6b122c2cc894450f from master