ruby-info: only run commands if the prompt needs the info

modules/ruby/functions/ruby-info

@@ -16,22 +16,23 @@ local version_formatted
 unset ruby_info
 typeset -gA ruby_info
 
+# Grab formatting for anything we might have to do
+zstyle -s ':prezto:module:ruby:info:version' format 'version_format'
+
+if [[ -n "$version_format" ]]; then
   if (( $+commands[rvm-prompt] )); then
     version="$(rvm-prompt)"
   elif (( $+commands[rbenv] )); then
     version="$(rbenv version-name)"
-  if [[ $version == "system" ]]; then
-    version=""
-  fi
   elif (( $+commands[ruby] )); then
     version="${${$(ruby --version)[(w)1,(w)2]}/ /-}"
   fi
 
   # Format version.
-if [[ -n "$version" ]]; then
+  if [[ -n "$version" && "$version" != "system" ]]; then
-  zstyle -s ':prezto:module:ruby:info:version' format 'version_format'
     zformat -f version_formatted "$version_format" "v:$version"
     ruby_info[version]="$version_formatted"
   fi
+fi
 
 # }