(customize-option): Refuse to customize

a variable that has no defcustom.  But if variable is autoloaded,
first try to load the library that defines it.

1 files changed, 22 insertions, 0 deletions

diff --git a/lisp/cus-edit.el b/lisp/cus-edit.el
index 4d4fc083553..77b946ece1a 100644
--- a/lisp/cus-edit.el
+++ b/lisp/cus-edit.el
@@ -868,6 +868,28 @@ are shown; the contents of those subgroups are initially hidden."
 (defun customize-option (symbol)
   "Customize SYMBOL, which must be a user option variable."
   (interactive (custom-variable-prompt))
+  ;; If we don't have SYMBOL's real definition loaded,
+  ;; try to load it.
+  (unless (get symbol 'custom-type)
+    (let ((loaddefs-file (locate-library "loaddefs.el" t))
+          file)
+      ;; See if it is autoloaded from some library.
+      (when loaddefs-file
+        (with-temp-buffer
+          (insert-file-contents loaddefs-file)
+          (when (re-search-forward (concat "^(defvar " (symbol-name symbol))
+                                   nil t)
+            (search-backward "\n;;; Generated autoloads from ")
+            (goto-char (match-end 0))
+            (setq file (buffer-substring (point)
+                                         (progn (end-of-line) (point)))))))
+      ;; If it is, load that library.
+      (when file
+        (when (string-match "\\.el\\'" file)
+          (setq file (substring file 0 (match-beginning 0))))
+        (load file))))
+  (unless (get symbol 'custom-type)
+    (error "Variable %s cannot be customized" symbol))
   (custom-buffer-create (list (list symbol 'custom-variable))
                         (format "*Customize Option: %s*"
                                 (custom-unlispify-tag-name symbol))))