Re: [PATCH v5 1/3] completion: add new __gitcompadd helper

[Felipe Contreras <felipe.contreras@gmail.com>]

On Wed, Oct 17, 2012 at 7:28 PM, SZEDER Gábor <szeder@ira.uka.de> wrote:
> On Sun, Oct 14, 2012 at 05:52:49PM +0200, Felipe Contreras wrote:

>> diff --git a/contrib/completion/git-completion.bash b/contrib/completion/git-completion.bash
>> index d743e56..01325de 100644
>> --- a/contrib/completion/git-completion.bash
>> +++ b/contrib/completion/git-completion.bash
>> @@ -225,6 +225,11 @@ _get_comp_words_by_ref ()
>>  fi
>>  fi
>>
>> +__gitcompadd ()
>> +{
>> +     COMPREPLY=($(compgen -W "$1" -P "$2" -S "$4" -- "$3"))
>> +}
>> +
>>  # Generates completion reply with compgen, appending a space to possible
>>  # completion words, if necessary.
>>  # It accepts 1 to 4 arguments:
>> @@ -238,13 +243,11 @@ __gitcomp ()
>>
>>       case "$cur_" in
>>       --*=)
>> -             COMPREPLY=()
>> +             __gitcompadd
>>               ;;
>>       *)
>>               local IFS=$'\n'
>> -             COMPREPLY=($(compgen -P "${2-}" \
>> -                     -W "$(__gitcomp_1 "${1-}" "${4-}")" \
>> -                     -- "$cur_"))
>> +             __gitcompadd "$(__gitcomp_1 "${1-}" "${4-}")" "${2-}" "$cur_" ""
>>               ;;
>>       esac
>>  }
>> @@ -261,7 +264,7 @@ __gitcomp ()
>>  __gitcomp_nl ()
>>  {
>>       local IFS=$'\n'
>> -     COMPREPLY=($(compgen -P "${2-}" -S "${4- }" -W "$1" -- "${3-$cur}"))
>> +     __gitcompadd "$1" "${2-}" "${3-$cur}" "${4- }"
>>  }
>
> I feel hesitant about this change.  One of the ways I'm exploring to
> fix the issues with shell metacharacters and expansion in compgen is
> to actually replace compgen.  We already iterate over all possible
> completion words in __gitcomp_1(), so it doesn't make much of a
> difference to do the filtering for the current word while we are at
> it.  However, the way __gitcompadd() encapsulates COMPREPLY=($(compgen
> ...)), and tha basic idea of never touching COMPREPLY directly make
> this basically impossible.

How is it impossible? You can still replace compgen, all you have to
do is modify __gitcompadd and replace that code with whatever custom
code you want. You can change the arguments and everything. The only
limitation is that it should be the only place where COMPREPLY is
modified, and all is good. Well, it doesn't have to be only _one_
place, but the less functions that do this, the better.

>>  __git_heads ()
>> @@ -486,7 +489,7 @@ __git_complete_remote_or_refspec ()
>>                       case "$cmd" in
>>                       push) no_complete_refspec=1 ;;
>>                       fetch)
>> -                             COMPREPLY=()
>> +                             __gitcompadd
>>                               return
>>                               ;;
>>                       *) ;;
>> @@ -502,7 +505,7 @@ __git_complete_remote_or_refspec ()
>>               return
>>       fi
>>       if [ $no_complete_refspec = 1 ]; then
>> -             COMPREPLY=()
>> +             __gitcompadd
>>               return
>>       fi
>>       [ "$remote" = "." ] && remote=
>> @@ -776,7 +779,7 @@ _git_am ()
>>                       "
>>               return
>>       esac
>> -     COMPREPLY=()
>> +     __gitcompadd
>
> These changes effectively run compgen in a subshell to generate an
> empty completion reply.  While it doesn't really matter on Linux,
> it'll add another half a tenth of a second delay in those cases on my
> Windows machine.  At least it should be conditional, i.e. $(compgen
> ...) shouldn't be executed when there are no possible completion
> words.
>
> However, I think those COMPREPLY=() assignments are pointless anyway.
> COMPREPLY is always empty when completion functions are invoked, so
> there is no need to explicitly set it to an empty array when we don't
> provide any words for completion.  Their only use is basically to
> explicitly tell us humans that in those cases we don't offer any words
> for completion.  But we don't do that consistently: there are several
> places without offering words for completion and without COMPREPLY=(),
> e.g. the '__git_has_doubledash && return' pattern.
>
> Perhaps it would be time to get rid of these COMPREPLY=() assignments?

I'm all for it, I never understood what was the purpose of that. I
believe zsh could benefit from this information to decide whether to
run the default completion (e.g. files) or not, but as you said, if
it's not used consistently for bash, there's no point in trying.

Cheers.

-- 
Felipe Contreras