fix(gnu-utils): reassign GNU utils on preexec (#10535)

The previous version rebound the `hash` and `rehash` builtins to
reassing GNU utils when they were called. This didn't take into
account that when `$PATH` changes, the commands are rehashed as
well.

This version adds a preexec hook to reassign the GNU utilities
before running any command, if and only if they aren't already
reassigned. This is checked by looking at the `whoami` command.

Fixes #10535

plugins/gnu-utils/gnu-utils.plugin.zsh

@@ -11,11 +11,8 @@ if [[ ! -x "${commands[gwhoami]}" ]]; then
 fi
 
 __gnu_utils() {
-  emulate -L zsh
+  local -a gcmds
-  local gcmds
   local gcmd
-  local cmd
-  local prefix
 
   # coreutils 
   gcmds=('g[' 'gbase64' 'gbasename' 'gcat' 'gchcon' 'gchgrp' 'gchmod'
@@ -43,36 +40,21 @@ __gnu_utils() {
     (( ${+commands[$gcmd]} )) || continue
     
     # This method allows for builtin commands to be primary but it's
-    # lost if hash -r or rehash -f is executed. Thus, those two 
+    # lost if hash -r or rehash is executed, or if $PATH is updated.
-    # functions have to be wrapped.
+    # Thus, a preexec hook is needed, which will only run if whoami
+    # is not already rehashed.
     #
     hash ${gcmd[2,-1]}=${commands[$gcmd]}
-
-    # This method generates wrapper functions.
-    # It will override shell builtins.
-    #
-    # eval "function $gcmd[2,-1]() { \"${prefix}/${gcmd//"["/"\\["}\" \"\$@\"; }"
-
-    # This method is inflexible since the aliases are at risk of being
-    # overridden resulting in the BSD coreutils being called.
-    #
-    # alias "$gcmd[2,-1]"="${prefix}/${gcmd//"["/"\\["}"
   done
 
   return 0
 }
-__gnu_utils
 
-function hash() {
+__gnu_utils_preexec() {
-  if [[ "$*" =~ "-(r|f)" ]]; then
+  # Run __gnu_utils when the whoami command is not already rehashed.
-    builtin hash "$@"
+  # This acts as a sign that we need to rehash all GNU utils.
-    __gnu_utils
+  [[ "${commands[whoami]}" = "${commands[gwhoami]}" ]] || __gnu_utils
-  else
-    builtin hash "$@"
-  fi
 }
 
-function rehash() {
+autoload -Uz add-zsh-hook
-  builtin rehash "$@"
+add-zsh-hook preexec __gnu_utils_preexec
-  __gnu_utils
-}