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

On Wed, Oct 17, 2012 at 7:28 PM, SZEDER Gábor [off-list ref] wrote:

On Sun, Oct 14, 2012 at 05:52:49PM +0200, Felipe Contreras wrote:

quoted

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.

quoted

 __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