Maybe remove-hook should remove all trace of localness?

Maybe remove-hook should remove all trace of localness?

[Marshall, Simon]

I noticed a package that checks the value of a local hook to see if it
is nil, meaning empty.
Unfortunately that is wrong because, currently, a local hook is (t) if
it is empty.
Only a non-local hook is nil if it is empty.

To see this, try:

(let (gotcha)
  (add-hook 'gotcha 'foo nil t)
  (remove-hook 'gotcha 'foo t)
  gotcha)
=> (t)

One solution is to fix the package, but perhaps a cleaner solution all
round would be to make remove-hook behave in a less surprising way?  And
also behave consistently, in that an add-hook/remove-hook pair would
leave the hook in the same state when the add/remove is local, as it
currently does when the add/remove is non-local.

I think this would do it, though perhaps there should be a
kill-local-hook for completeness.
Is it better?  I think so.  Does it have nasty side-effects?  Not sure.

diff -c /rvcarma/marshals/ftp/emacs-21.1.90/lisp/subr.el.\~1\~
/rvcarma/marshals/ftp/emacs-21.1.90/lisp/subr.el
*** /rvcarma/marshals/ftp/emacs-21.1.90/lisp/subr.el.~1~	Thu Aug
9 15:52:27 2001
--- /rvcarma/marshals/ftp/emacs-21.1.90/lisp/subr.el	Mon Apr  8
14:11:28 2002
***************
*** 776,782 ****
      ;;	       (not (member (cons 'not function) hook-value)))
      ;;  (push (cons 'not function) hook-value))
      ;; Set the actual variable
!     (if local (set hook hook-value) (set-default hook hook-value))))
  
  (defun add-to-list (list-var element &optional append)
    "Add to the value of LIST-VAR the element ELEMENT if it isn't there
yet.
--- 776,786 ----
      ;;	       (not (member (cons 'not function) hook-value)))
      ;;  (push (cons 'not function) hook-value))
      ;; Set the actual variable
!     (if (not local)
! 	(set-default hook hook-value)
!       (if (equal hook-value '(t))
! 	  (kill-local-variable hook)
! 	(set hook hook-value)))))
  
  (defun add-to-list (list-var element &optional append)
    "Add to the value of LIST-VAR the element ELEMENT if it isn't there
yet.

Diff finished at Mon Apr  8 14:12:23

Re: Maybe remove-hook should remove all trace of localness?

[Richard Stallman]

I like your change.   Now that there is no longer a need
to call add-local-hook, we don't need a kill-local-hook,
and removing the (t) when it is temporarily unnecessary
cannot do any harm.

I will install it.