Re: parse-options does not recognize "unspecified" behavior

From: Eric Sunshine <sunshine@sunshineco.com>
Date: Mar 16, 2016, 21:37 UTC
Message-ID: <CAPig+cRKyaUefz0qj6unkaiPg25=Xi2WorQE4Fm46CCf00UbHQ@mail.gmail.com>
In-Reply-To: <20160316212308.GA4538@sigill.intra.peff.net>

On Wed, Mar 16, 2016 at 5:23 PM, Jeff King <peff@peff.net> wrote:

Show 19 quoted lines

> On Thu, Mar 17, 2016 at 02:36:51AM +0530, Pranit Bauva wrote:
>> I agree to you on the point that parse-options should not care about
>> the value passed to it. But I think plainly incrementing the value of
>> the variable is not a very nice way. I have an another approach to it.
>> The parse-options will first store a temporary structure. If there is
>> some changes (not the "--no-" ones) then it sets the respective
>> variable in temporary structure to the set value. If "--no-" is passed
>> then it writes the "reset" value to the respective variable in
>> temporary structure. If nothing about that options is specified then
>> it copies the respective variable from original to temporary. After
>> completing the entire process, it can copy temporary structure to the
>> original structure.
>>
>> What are your opinions about this?
>
> I don't think that would produce the wrong behavior, but it seems like a
> very complicated solution to a problem that can easily be solved by just
> following the usual conventions (that verbose starts at 0, options make
> it go up or down, and "--no-" resets it to zero).

I agree that this is overly complicated.

> Perhaps it would make more sense if I understood what your goal was in
> setting verbose to -1 in the first place.

The goal comes from his GSoC microproject. Specifically, Pranit wants an "unspecified" value. The reason is that he is adding a commit.verbose=<level> config variable to back the existing git-commit --verbose option. Any use of --verbose (one or more times) or --no-verbose should override the config.verbose value altogether, so he wants a way to know if --verbose or --no-verbose was used; hence the "unspecified" value. And, really, this issue isn't necessarily specific to git-commit. It could apply to any command that understands verbosity levels and wants to be able to get them from both a config variable and a command-line option.

A much easier solution would be to update OPT_VERBOSE() to understand that negative values are "unspecified", and then --verbose would (pseudocode):

    if (value < 0)
        value = 0
    value++;

and --no-verbose would:

    value = 0

That should be compatible with existing clients of OPT__VERBOSE() which initialize the value to 0, and should satisfy Pranit's case; he can initialize it to -1, and if it is still -1 when option parsing is done, then he knows that neither --verbose nor --no-verbose was seen.