feat(_comp_compgen_{filedir,set}): define exit status

bash_completion

@@ -665,12 +665,14 @@ _comp_compgen()
 # caller _comp_compgen, the words are appended to the existing elements of the
 # array instead of replacing the existing elements.  This function ignores
 # ${cur-} or the prefix specified by `-v CUR`.
+# @return 0 if at least one completion is generated, or 1 otherwise.
 # @since 2.12
 _comp_compgen_set()
 {
     local _append=${_comp_compgen__append-}
     local _var=${_comp_compgen__var-COMPREPLY}
     eval -- "$_var${_append:++}=(\"\$@\")"
+    (($#))
 }
 
 # Simply split the text and generate completions.  This function should be used
@@ -1004,6 +1006,7 @@ _comp_quote_compgen()
 # @param $1  If `-d', complete only on directories.  Otherwise filter/pick only
 #            completions with `.$1' and the uppercase version of it as file
 #            extension.
+# @return 0 if at least one completion is generated, or 1 otherwise.
 #
 # @since 2.12
 _comp_compgen_filedir()