(describe-variable-custom-version-info): New function to return

variable's version or package version note.
(describe-variable): Use it, display result.

diff --git a/lisp/help-fns.el b/lisp/help-fns.el
index f62fadc22b53b571042a04ab228c2fdf2f8a4abb..bf57824dcf0faaa68a47a9ec0fd778ea3f101600 100644 (file)
--- a/lisp/help-fns.el
+++ b/lisp/help-fns.el
@@ -456,6 +456,28 @@ If ANY-SYMBOL is non-nil, don't insist the symbol be bound."
              (and (or any-symbol (boundp sym)) sym)))))
       0))
 
+(defun describe-variable-custom-version-info (variable)
+  (let ((custom-version (get variable 'custom-version))
+       (cpv (get variable 'custom-package-version))
+       (output nil))
+    (if custom-version
+       (setq output
+             (format "This variable was introduced, or its default value was changed, in\nversion %s of Emacs.\n"
+                     custom-version))
+      (when cpv
+       (let* ((package (car-safe cpv))
+              (version (car (cdr-safe cpv)))
+              (pkg-versions (assq package customize-package-emacs-version-alist))
+              (emacsv (cdr (assoc version pkg-versions))))
+         (if (and package version)
+             (setq output
+                   (format (concat "This variable was introduced, or its default value was changed, in\nversion %s of the %s package"
+                                   (if emacsv
+                                       (format " that is part of Emacs %s" emacsv))
+                                   ".\n")
+                           version package))))))
+    output))
+
 ;;;###autoload
 (defun describe-variable (variable &optional buffer frame)
   "Display the full documentation of VARIABLE (a symbol).
@@ -646,16 +668,23 @@ it is displayed along with the global value."
              (with-current-buffer standard-output
                (insert (or doc "Not documented as a variable."))))
            ;; Make a link to customize if this variable can be customized.
-           (if (custom-variable-p variable)
-               (let ((customize-label "customize"))
+           (when (custom-variable-p variable)
+             (let ((customize-label "customize"))
+               (terpri)
+               (terpri)
+               (princ (concat "You can " customize-label " this variable."))
+               (with-current-buffer standard-output
+                 (save-excursion
+                   (re-search-backward
+                    (concat "\\(" customize-label "\\)") nil t)
+                   (help-xref-button 1 'help-customize-variable variable))))
+             ;; Note variable's version or package version
+             (let ((output (describe-variable-custom-version-info variable)))
+               (when output
                  (terpri)
                  (terpri)
-                 (princ (concat "You can " customize-label " this variable."))
-                 (with-current-buffer standard-output
-                   (save-excursion
-                     (re-search-backward
-                      (concat "\\(" customize-label "\\)") nil t)
-                     (help-xref-button 1 'help-customize-variable variable)))))
+                 (princ output))))
+
            (print-help-return-message)
            (save-excursion
              (set-buffer standard-output)