fix(_comp_compgen_*): avoid conflicts with "-v var"

[akinomyoga]

To avoid conflicts between local variables and variable names specified by _comp_compgen -v var, the local variables basically need to have the name _foo.

Handling of conflicts with internal generator calls

When a generator needs to call other generators to store results in a local variable, the local variable name cannot have the name _foo because it is rejected by the internal generator calls. In such a case, we first declare the variable without the underscore (e.g. foo), call the internal generator to store the result to foo, move the results to an underscored variable (_foo), and remove the local variable foo by _comp_unlocal foo. The current version of the PR uses this approach.

However, maybe this is too complicated. Another possibility is to add a new option _comp_compgen -U foo to internally perform _comp_unlocal foo immediately before storing the results.

[akinomyoga]

Another possibility is to add a new option _comp_compgen -U foo to internally perform _comp_unlocal foo immediately before storing the results.

This is an example implementation for this direction.

diff --git a/bash_completion b/bash_completion
index 98c67eb0..0799824e 100644
--- a/bash_completion
+++ b/bash_completion
@@ -512,6 +512,7 @@ _comp_compgen()
     local _dir=""
     local _ifs=$' \t\n' _has_ifs=""
     local _icmd="" _xcmd=""
+    local -a _upvars=()

     local _old_nocasematch=""
     if shopt -q nocasematch; then
@@ -519,7 +520,7 @@ _comp_compgen()
         shopt -u nocasematch
     fi
     local OPTIND=1 OPTARG="" OPTERR=0 _opt
-    while getopts ':av:Rc:C:lF:i:x:' _opt "$@"; do
+    while getopts ':av:U:Rc:C:lF:i:x:' _opt "$@"; do
         case $_opt in
             a) _append=set ;;
             v)
@@ -529,6 +530,16 @@ _comp_compgen()
                 fi
                 _var=$OPTARG
                 ;;
+            U)
+                if [[ $OPTARG == @(*[^_a-zA-Z0-9]*|[0-9]*|'') ]]; then
+                    printf 'bash_completion: %s: -U: invalid variable name `%s'\''\n' "$FUNCNAME" "$OPTARG" >&2
+                    return 2
+                else if [[ $OPTARG == @(_*|IFS|OPTIND|OPTARG|OPTERR) ]]; then
+                    printf 'bash_completion: %s: -U: `%s'\'' unneccessary to mark upvar\n' "$FUNCNAME" "$OPTARG" >&2
+                    return 2
+                fi
+                _upvars+=("$OPTARG")
+                ;;
             c) _cur=$OPTARG ;;
             R) _cur="" ;;
             C)
@@ -573,6 +584,9 @@ _comp_compgen()
         if [[ $_has_ifs ]]; then
             printf 'bash_completion: %s: `-l'\'' and `-F sep'\'' are not supported for generators\n' "$FUNCNAME" >&2
             return 2
+        elif ((${#_upvars[@]})); then
+            printf 'bash_completion: %s: `-U var'\'' is not supported for generator calls\n' "$FUNCNAME" >&2
+            return 2
         fi

         local -a _generator
@@ -653,6 +664,7 @@ _comp_compgen()
         return
     }

+    ((${#_upvars[@]})) && _comp_unlocal "${_upvars[@]}"
     _comp_split -l ${_append:+-a} "$_var" "$_result"
 }

[akinomyoga]

I decided to use the approach of the previous reply #1028 (comment).

[akinomyoga]

Rebased & resolved conflicts.

[akinomyoga]

Added fixes mentioned in #1026.

[scop]

Slowly getting started with this, got some trivial bits merged out of the way.

[akinomyoga]

Rebased.

[scop]

I think it will take me quite some time to become comfortable with this, but I do see the point and think I even understand some parts of this stuff :) So let's go with this, thanks!

[akinomyoga]

Thanks