[PATCH 2 of 7 v3 flags] fancyopts: disallow true as a boolean flag default (API)

[Pierre-Yves David]

On 09/14/2016 06:37 PM, Yuya Nishihara wrote:
> On Wed, 14 Sep 2016 11:52:59 -0400, Augie Fackler wrote:
>>> On Sep 14, 2016, at 11:30, Yuya Nishihara <yuya at tcha.org> wrote:
>> Is the idea something like:
>>
>> fancyopts.py:
>>
>> unsetbool = object()
>>
>> in commands.py:
>>
>>  diffopts = [
>> -     ('a', 'text', None, _('treat all files as text')),
>> +     ('a', 'text', fancyopts.unsetbool, _('treat all files as text')),
>> -     ('g', 'git', None, _('use git extended diff format')),
>> +     ('g', 'git', fancyopts.unsetbool, _('use git extended diff format')),
>> -     ('', 'nodates', None, _('omit dates from diff headers'))
>> +     ('', 'nodates', fancyopts.unsetbool, _('omit dates from diff headers'))
>>  ]
>
> Yes.
>
>> And then we could synthesize negated versions only for booleans that have
>> fancyopts.unsetbool as the default?
>
> No. My idea is to not set 'git' at all.
>
>   default:  {}  # not {'git': None}
>   --git:    {'git': True}
>   --no-git: {'git': False}
>
> and falls back to ui.configbool if 'git' not in opts.
>
> My point is diffopts are special in that their defaults are configurable. Many
> other boolean options have no such feature, so they can simply be default=None
> (or False.)

So far, the option parsing logic have ensure options always exist and 
have some value in the 'opts' dictionary. Changing this would be a 
massive API breakage. I really don't think we should go this route.

-- 
Pierre-Yves David