On Fri, Oct 14, 2022 at 11:11 AM Junio C Hamano <gitster@xxxxxxxxx> wrote:
>
> Tao Klerks <tao@xxxxxxxxxx> writes:
>
> > 1. Why add an OPT_CALLBACK_F arg handler, rather than keeping a simple
> > OPT_BOOL arg type?
> > Because OPT_BOOL always overwrites with either true or false, so in
> > order to have use_gui_tool retain its "_BY_CONFIG" value in the
> > absence of an arg, the explicit arg handler function is required.
>
> That is exactly why you want to initialize the variable to something
> other than 0 or 1 (say "-1") and use that as "not explicitly
> specified from the command line" aka _BY_CONFIG value, isn't it?
>
> And once you do so, you do not need callback and you do not need
> enum. The original "int" can take tri-state, (unspecified = -1,
> false = 0, true = 1).
>
> Am I missing something?
Heh, I guess one of us must be, and it's probably me :)
My understanding, from ad-hoc testing, is that using OPT_BOOL causes
the target variable ("use_gui_tool" in this case) to *always* be set
to either "1" or "0", regardless of whether the user sets the main
flag, the --no form of the flag, or sets nothing at all. As far as I
can tell, OPT_BOOL never leaves the original value, so it cannot be
used to track tri-state "true, false or not specified" logic. Maybe I
made a mistake somewhere, and that's not really or always how it
behaves.
I can re-test, and/or try to dig into the option parsing logic to
understand how it works - the time I tried, I got hopelessly lost and
was relieved to find that OPT_CALLBACK_F existed and seemed to be used
for exactly these kinds of use cases.
