[archive] Check unrar with commands array

“unrar-free returns the error code 1 when run without arguments, thus
failing the presence check.” as reported at sorin-ionescu/prezto#1383

Reformat code and use one-liners instead of if/then/fi. And we don’t
need to separate local definitions from assignments anymore starting
from zsh 5.2.

modules/archive/functions/archive

@@ -2,8 +2,6 @@
 # Creates archive files
 #
 
-local archive_name dir_to_archive
-
 if (( ${#} != 2 )); then
   print "usage: ${0} [archive_name.ext] [/path/to/include/in/archive]" >&2
   return 1
@@ -13,9 +11,9 @@ fi
 # so we don't need any argc check here.
 
 # strip the path, just in case one is provided for some reason
-archive_name="${1:t}"
+local archive_name="${1:t}"
 # use absolute paths, and follow symlinks
-dir_to_archive="${2}"
+local dir_to_archive="${2}"
 
 # if the directory doesn't exist, quit. Nothing to archive
 if [[ ! -e "${dir_to_archive}" ]]; then

modules/archive/functions/unarchive

@@ -2,8 +2,6 @@
 # Unarchives files
 #
 
-local archive_name
-
 if (( ${#} != 1 )); then
   print "usage: ${0} [archive.ext]" >&2
   return 1
@@ -15,7 +13,7 @@ if [[ ! -s ${1} ]]; then
 fi
 
 # strip the path, just in case one is provided for some reason
-archive_name="${1:t}"
+local archive_name="${1:t}"
 
 # using unpigz/pbunzip2 provides little to decompression time; the benefit is mainly in compression time.
 # setting it as an alias in the init.zsh file should be sufficient here.
@@ -34,8 +32,7 @@ case "${archive_name}" in
   (*.lzma) unlzma "${archive_name}" ;;
   (*.Z) uncompress "${archive_name}" ;;
   (*.zip) unzip "${archive_name}";;
-  (*.rar) unrar &> /dev/null \
-    && unrar x -ad "${archive_name}" \
+  (*.rar) (( $+{commands[unrar]} )) && unrar x -ad "${archive_name}" \
     || rar x -ad "${archive_name}" ;;
   (*.7z|*.001) 7za x "${archive_name}" ;;
   (*) print "${0}: unknown archive type: ${archive_name}" ;;

modules/archive/init.zsh

@@ -7,23 +7,11 @@
 #
 # pigz
 #
-
-if (( ${+commands[pigz]} )); then
-  alias gzip='pigz'
-fi
-
-if (( ${+commands[unpigz]} )); then
-  alias gunzip='unpigz'
-fi
+(( ${+commands[pigz]} )) && alias gzip='pigz'
+(( ${+commands[unpigz]} )) && alias gunzip='unpigz'
 
 #
 # pbzip2
 #
-
-if (( ${+commands[pbzip2]} )); then
-  alias bzip2='pbzip2'
-fi
-
-if (( ${+commands[pbunzip2]} )); then
-  alias bunzip2='pbunzip2'
-fi
+(( ${+commands[pbzip2]} )) && alias bzip2='pbzip2'
+(( ${+commands[pbunzip2]} )) && alias bunzip2='pbunzip2'