Make function erc-scrolltobottom-mode idempotent

* lisp/erc/erc-goodies.el (erc-scrolltobottom-mode)
(erc-scrolltobottom-enable): Always remove hook functions whose
membership hinges on the value of `erc-scrolltobottom-all'.  In ERC 5.6,
an init file's `setopt' form containing an `erc-modules' assignment
before an `erc-scrolltobottom-all' one would result in conflicting sets
of hook members come `erc-open'.  Having such option-dependent branching
in module setup, while difficult to maintain, is a long held ERC
practice, as seen in functions like `erc-nickserv-identify-mode'.
Making all new modules "local" may be the most manageable solution
because existing global modules can't be made to require prior
deactivation.

1 files changed, 5 insertions, 0 deletions

diff --git a/lisp/erc/erc-goodies.el b/lisp/erc/erc-goodies.el
index 24a3205e0cd..2a787f3e014 100644
--- a/lisp/erc/erc-goodies.el
+++ b/lisp/erc/erc-goodies.el
@@ -87,10 +87,15 @@ be experimental.  It currently only works with Emacs 28+."
    (unless erc--updating-modules-p (erc-buffer-do #'erc--scrolltobottom-setup))
    (if erc-scrolltobottom-all
        (progn
+         (remove-hook 'erc-insert-done-hook #'erc-possibly-scroll-to-bottom)
          (add-hook 'erc-insert-pre-hook #'erc--scrolltobottom-on-pre-insert 25)
          (add-hook 'erc-pre-send-functions #'erc--scrolltobottom-on-pre-insert)
          (add-hook 'erc-insert-done-hook #'erc--scrolltobottom-all)
          (add-hook 'erc-send-completed-hook #'erc--scrolltobottom-all))
+     (remove-hook 'erc-insert-pre-hook #'erc--scrolltobottom-on-pre-insert)
+     (remove-hook 'erc-pre-send-functions #'erc--scrolltobottom-on-pre-insert)
+     (remove-hook 'erc-insert-done-hook #'erc--scrolltobottom-all)
+     (remove-hook 'erc-send-completed-hook #'erc--scrolltobottom-all)
      (add-hook 'erc-insert-done-hook #'erc-possibly-scroll-to-bottom)))
   ((remove-hook 'erc-mode-hook #'erc--scrolltobottom-setup)
    (erc-buffer-do #'erc--scrolltobottom-setup)