(define-derived-mode): Remove defvar for mode hook. (It conflicted

with defcustoms for some mode hooks.)  Use the `variable-documentation'
property to give the mode hook a docstring and expand that docstring.

1 files changed, 6 insertions, 1 deletions

diff --git a/lisp/emacs-lisp/derived.el b/lisp/emacs-lisp/derived.el
index 8e1f79f95ee..e595ff92a39 100644
--- a/lisp/emacs-lisp/derived.el
+++ b/lisp/emacs-lisp/derived.el
@@ -194,7 +194,12 @@ See Info node `(elisp)Derived Modes' for more details."
                      parent child docstring syntax abbrev))
 
     `(progn
-       (defvar ,hook nil ,(format "Hook run when entering %s mode." name))
+       (unless (get  ',hook 'variable-documentation)
+         (put ',hook 'variable-documentation
+              ,(format "Hook run when entering %s mode.
+No problems result if this variable is not bound.
+`add-hook' automatically binds it.  (This is true for all hook variables.)"
+                       name)))
        (defvar ,map (make-sparse-keymap))
        ,(if declare-syntax
             `(defvar ,syntax (make-syntax-table)))