* lisp/subr.el (add-hook): Turn `append` into `depth` (bug#35508)

Make it possible to control the relative ordering of functions on hooks by
specifying `depth` in the same was as was possible with `add-function`.

* lisp/electric.el (electric--sort-post-self-insertion-hook):
Delete function.
(electric-indent-mode, electric-layout-mode, electric-quote-mode):
* lisp/elec-pair.el (electric-pair-mode): Use new `depth` arg instead of
electric--sort-post-self-insertion-hook.

* lisp/emacs-lisp/syntax.el (syntax-propertize, syntax-ppss):
Use new `depth` arg to make sure noone accidentally gets added
after syntax-ppss-flush-cache.

* doc/lispref/modes.texi (Setting Hooks): Document new `depth` arg.

* test/lisp/subr-tests.el (subr-tests-add-hook-depth): New test.

1 files changed, 6 insertions, 23 deletions

diff --git a/lisp/electric.el b/lisp/electric.el
index 07da2f1d9e7..53e53bd975c 100644
--- a/lisp/electric.el
+++ b/lisp/electric.el
@@ -190,17 +190,6 @@ Returns nil when we can't find this char."
                            (eq (char-before) last-command-event)))))
       pos)))
 
-(defun electric--sort-post-self-insertion-hook ()
-  "Ensure order of electric functions in `post-self-insertion-hook'.
-
-Hooks in this variable interact in non-trivial ways, so a
-relative order must be maintained within it."
-  (setq-default post-self-insert-hook
-                (sort (default-value 'post-self-insert-hook)
-                      #'(lambda (fn1 fn2)
-                          (< (or (if (symbolp fn1) (get fn1 'priority)) 0)
-                             (or (if (symbolp fn2) (get fn2 'priority)) 0))))))
-
 ;;; Electric indentation.
 
 ;; Autoloading variables is generally undesirable, but major modes
@@ -297,8 +286,6 @@ or comment."
                 (indent-according-to-mode)
               (error (throw 'indent-error nil)))))))))
 
-(put 'electric-indent-post-self-insert-function 'priority  60)
-
 (defun electric-indent-just-newline (arg)
   "Insert just a newline, without any auto-indentation."
   (interactive "*P")
@@ -341,8 +328,8 @@ use `electric-indent-local-mode'."
         (remove-hook 'post-self-insert-hook
                      #'electric-indent-post-self-insert-function))
     (add-hook 'post-self-insert-hook
-              #'electric-indent-post-self-insert-function)
-    (electric--sort-post-self-insertion-hook)))
+              #'electric-indent-post-self-insert-function
+              60)))
 
 ;;;###autoload
 (define-minor-mode electric-indent-local-mode
@@ -472,8 +459,6 @@ If multiple rules match, only first one is executed.")
               ('after-stay (save-excursion (funcall nl-after)))
               ('around (funcall nl-before) (funcall nl-after))))))))
 
-(put 'electric-layout-post-self-insert-function 'priority  40)
-
 ;;;###autoload
 (define-minor-mode electric-layout-mode
   "Automatically insert newlines around some chars.
@@ -482,8 +467,8 @@ The variable `electric-layout-rules' says when and how to insert newlines."
   :global t :group 'electricity
   (cond (electric-layout-mode
          (add-hook 'post-self-insert-hook
-                   #'electric-layout-post-self-insert-function)
-         (electric--sort-post-self-insertion-hook))
+                   #'electric-layout-post-self-insert-function
+                   40))
         (t
          (remove-hook 'post-self-insert-hook
                       #'electric-layout-post-self-insert-function))))
@@ -623,8 +608,6 @@ This requotes when a quoting key is typed."
                     (replace-match (string q>>))
                     (setq last-command-event q>>))))))))))
 
-(put 'electric-quote-post-self-insert-function 'priority 10)
-
 ;;;###autoload
 (define-minor-mode electric-quote-mode
   "Toggle on-the-fly requoting (Electric Quote mode).
@@ -651,8 +634,8 @@ use `electric-quote-local-mode'."
         (remove-hook 'post-self-insert-hook
                      #'electric-quote-post-self-insert-function))
     (add-hook 'post-self-insert-hook
-              #'electric-quote-post-self-insert-function)
-    (electric--sort-post-self-insertion-hook)))
+              #'electric-quote-post-self-insert-function
+              10)))
 
 ;;;###autoload
 (define-minor-mode electric-quote-local-mode