Hide obsolete options in most customize commands

* lisp/cus-edit.el (custom--filter-obsolete-variables): New defun.
* lisp/cus-edit.el (customize-changed-options)
(customize-apropos, custom-group-value-create): Hide obsolete user
options.  (Bug#44598)
* test/lisp/cus-edit-tests.el: New file.

etc/NEWS

@@ -712,6 +712,16 @@ This file was a compatibility kludge which is no longer needed.
 To revert to the previous behavior,
 '(setq lisp-indent-function 'lisp-indent-function)' from 'lisp-mode-hook'.
 
+** Customize
+
+*** Most customize commands now hide obsolete user options.
+Obsolete user options are no longer shown in the listings produced by
+the commands `customize', `customize-group', `customize-apropos' and
+`customize-changed-options'.
+
+To customize obsolete user options, use `customize-option' or
+`customize-saved'.
+
 ** Edebug
 
 +++

lisp/cus-edit.el

@@ -1298,7 +1298,8 @@ that were added or redefined since that version."
 	       (if (custom-facep symbol)
 		   (push (list symbol 'custom-face) found)))))))
     (if found
-	(custom-buffer-create (custom-sort-items found t 'first)
+        (custom-buffer-create (custom--filter-obsolete-variables
+                               (custom-sort-items found t 'first))
 			      "*Customize Changed Options*")
       (user-error "No user option defaults have been changed since Emacs %s"
                   since-version))))
@@ -1504,7 +1505,8 @@ If TYPE is `groups', include only groups."
 						(symbol-name type))
 	     pattern))
     (custom-buffer-create
-     (custom-sort-items found t custom-buffer-order-groups)
+     (custom--filter-obsolete-variables
+      (custom-sort-items found t custom-buffer-order-groups))
      "*Customize Apropos*")))
 
 ;;;###autoload
@@ -4232,6 +4234,13 @@ and so forth.  The remaining group tags are shown with `custom-group-tag'."
 	(insert "--------")))
   (widget-default-create widget))
 
+(defun custom--filter-obsolete-variables (items)
+  "Filter obsolete variables from ITEMS."
+  (seq-remove (lambda (item)
+                (and (eq (nth 1 item) 'custom-variable)
+                     (get (nth 0 item) 'byte-obsolete-variable)))
+              items))
+
 (defun custom-group-members (symbol groups-only)
   "Return SYMBOL's custom group members.
 If GROUPS-ONLY is non-nil, return only those members that are groups."
@@ -4437,12 +4446,13 @@ This works for both graphical and text displays."
 					     ?\s))
 	   ;; Members.
 	   (message "Creating group...")
-	   (let* ((members (custom-sort-items
-			    members
-			    ;; Never sort the top-level custom group.
-			    (unless (eq symbol 'emacs)
-			      custom-buffer-sort-alphabetically)
-			    custom-buffer-order-groups))
+           (let* ((members (custom--filter-obsolete-variables
+                            (custom-sort-items
+                             members
+                             ;; Never sort the top-level custom group.
+                             (unless (eq symbol 'emacs)
+                               custom-buffer-sort-alphabetically)
+                             custom-buffer-order-groups)))
 		  (prefixes (widget-get widget :custom-prefixes))
 		  (custom-prefix-list (custom-prefix-add symbol prefixes))
 		  (have-subtitle (and (not (eq symbol 'emacs))

test/lisp/cus-edit-tests.el

@@ -0,0 +1,80 @@
+;;; cus-edit-tests.el --- Tests for cus-edit.el  -*- lexical-binding: t -*-
+
+;; Copyright (C) 2020 Free Software Foundation, Inc.
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software: you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;;; Code:
+
+(require 'ert)
+(require 'ert-x)
+(require 'cus-edit)
+
+(defmacro with-cus-edit-test (buffer &rest body)
+  (declare (indent 1))
+  `(save-window-excursion
+     (unwind-protect
+         (progn ,@body)
+       (when-let ((buf (get-buffer ,buffer)))
+         (kill-buffer buf)))))
+
+
+;;;; showing/hiding obsolete options
+
+(defgroup cus-edit-tests nil "test"
+  :group 'test-group)
+
+(defcustom cus-edit-tests--obsolete-option-tag nil
+  "This should never be removed; it is obsolete for testing purposes."
+  :type 'boolean
+  :version "917.10") ; a super high version number
+(make-obsolete-variable 'cus-edit-tests--obsolete-option-tag nil "X.X-test")
+(defconst cus-edit-tests--obsolete-option-tag
+  (custom-unlispify-tag-name 'cus-edit-tests--obsolete-option-tag))
+
+(ert-deftest cus-edit-tests-customize-apropos/hide-obsolete ()
+  (with-cus-edit-test "*Customize Apropos*"
+    (customize-apropos "cus-edit-tests")
+    (should-not (search-forward cus-edit-tests--obsolete-option-tag nil t))))
+
+(ert-deftest cus-edit-tests-customize-changed-options/hide-obsolete ()
+  (with-cus-edit-test "*Customize Changed Options*"
+    (customize-changed-options "917.2") ; some future version
+    (should-not (search-forward cus-edit-tests--obsolete-option-tag nil t))))
+
+(ert-deftest cus-edit-tests-customize-group/hide-obsolete ()
+  "Check that obsolete variables do not show up."
+  (with-cus-edit-test "*Customize Group: Cus Edit Tests*"
+    (customize-group 'cus-edit-tests)
+    (should-not (search-forward cus-edit-tests--obsolete-option-tag nil t))))
+
+(ert-deftest cus-edit-tests-customize-option/show-obsolete ()
+  (with-cus-edit-test "*Customize Option: Cus Edit Tests Obsolete Option Tag*"
+    (customize-option 'cus-edit-tests--obsolete-option-tag)
+    (goto-char (point-min))
+    (should (search-forward cus-edit-tests--obsolete-option-tag nil t))))
+
+(ert-deftest cus-edit-tests-customize-saved/show-obsolete ()
+  ;; FIXME: How to test for saved options?
+  :expected-result :failed
+  (with-cus-edit-test "*Customize Saved*"
+    (customize-saved)
+    (should (search-forward cus-edit-tests--obsolete-option-tag nil t))))
+
+(provide 'cus-edit-tests)
+;;; cus-edit-tests.el ends here