(define-obsolete-variable-alias): Doc fix.

Maybe copy some custom properties from old to new name.  (Bug#4706)

2 files changed, 24 insertions, 15 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index d48b95612b3..883285b20c5 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2009-10-16  Glenn Morris  <rgm@gnu.org>
+
+        * emacs-lisp/byte-run.el (define-obsolete-variable-alias): Doc fix.
+        Maybe copy some custom properties from old to new name.  (Bug#4706)
+
 2009-10-16  Juanma Barranquero  <lekktu@gmail.com>
 
         * subr.el (error, sit-for, start-process-shell-command)
diff --git a/lisp/emacs-lisp/byte-run.el b/lisp/emacs-lisp/byte-run.el
index 5c4eeae0cde..7b0faec655c 100644
--- a/lisp/emacs-lisp/byte-run.el
+++ b/lisp/emacs-lisp/byte-run.el
@@ -175,28 +175,32 @@ was first made obsolete, for example a date or a release number."
 (defmacro define-obsolete-variable-alias (obsolete-name current-name
                                                  &optional when docstring)
   "Make OBSOLETE-NAME a variable alias for CURRENT-NAME and mark it obsolete.
-
-\(define-obsolete-variable-alias 'old-var 'new-var \"22.1\" \"old-var's doc.\")
-
-is equivalent to the following two lines of code:
-
-\(defvaralias 'old-var 'new-var \"old-var's doc.\")
-\(make-obsolete-variable 'old-var 'new-var \"22.1\")
+This uses `defvaralias' and `make-obsolete-variable' (which see).
+See the Info node `(elisp)Variable Aliases' for more details.
 
 If CURRENT-NAME is a defcustom (more generally, any variable
 where OBSOLETE-NAME may be set, e.g. in a .emacs file, before the
 alias is defined), then the define-obsolete-variable-alias
-statement should be placed before the defcustom.  This is so that
-any user customizations are applied before the defcustom tries to
-initialize the variable (this is due to the way `defvaralias' works).
-Exceptions to this rule occur for define-obsolete-variable-alias
-statements that are autoloaded, or in files dumped with Emacs.
-
-See the docstrings of `defvaralias' and `make-obsolete-variable' or
-Info node `(elisp)Variable Aliases' for more details."
+statement should be evaluated before the defcustom, if user
+customizations are to be respected.  The simplest way to achieve
+this is to place the alias statement before the defcustom (this
+is not necessary for aliases that are autoloaded, or in files
+dumped with Emacs).  This is so that any user customizations are
+applied before the defcustom tries to initialize the
+variable (this is due to the way `defvaralias' works).
+
+For the benefit of `custom-set-variables', if OBSOLETE-NAME has
+any of the following properties, they are copied to
+CURRENT-NAME, if it does not already have them:
+'saved-value, 'saved-variable-comment."
   (declare (doc-string 4))
   `(progn
      (defvaralias ,obsolete-name ,current-name ,docstring)
+     ;; See Bug#4706.
+     (mapc (lambda (prop) (or (get ,current-name prop)
+                              (put ,current-name prop
+                                   (get ,obsolete-name prop))))
+           '(saved-value saved-variable-comment))
      (make-obsolete-variable ,obsolete-name ,current-name ,when)))
 (set-advertised-calling-convention
  ;; New code should always provide the `when' argument.