Document Widget.build_attrs() signature change in Django 1.11

[Melvyn Sopacua]

While build_attrs is undocumented (not sure why, since many widgets override render() and make use of build_attrs) and changed it's method signature in 1.11 by removing kwargs.

This isn't mentioned in the release notes.

A compatibility method could look something like this:

    def build_attrs(self, extra_attrs=None, **kwargs):
        # Django 1.11 changed method signature by removing kwargs
        if extra_attrs:
            kwargs.update(extra_attrs)
        return super().build_attrs(extra_attrs=kwargs)

An update of the release notes would be very welcome.

[brian houston morrow]

Created ​pull request documenting the removal of kwargs as well as Widget.build_attrs.

This is the first time Widget.build_attrs is documented. Does it make sense to document this in other stable branches as well? If so, would those be appropriate for this PR?

[Melvyn Sopacua]

I don't think it should be documented.

The apparent reason for making this backwards-incompatible change was that it was deemed internal (because it was not documented).
However - it is widely used in the field, as Widget.render() used to be abstract and widget implementors copied code from InputWidget and friends, which used build_attrs.

But because it is widely used and incompatible, it should be noted in the release notes.

Personally, I expect this method to be removed, as it's nothing more then a wrapper for dict.update(), with no added value (the fact that you could pass keyword arguments that would be added as attributes was it's added value, as that is much easier to type and read).

[brian houston morrow]

Okay, that makes sense.
I've removed that part of the commit and left the remaining changes to the 1.11 release note in this ​pull request.

[Tim Graham <timograham@…>]

In e86f478:

Fixed #28095 -- Doc'd Widget.build_attrs() signature change in Django 1.11.

[Tim Graham <timograham@…>]

In 4bdc832:

[1.11.x] Fixed #28095 -- Doc'd Widget.build_attrs() signature change in Django 1.11.

Backport of e86f4786a7f39b0ed833c0699addf0c27811d864 from master