bug#41721: 28.0.50; "f is undefined" in list-packages buffer

[Basil L. Contovounesios]

tags 41721 + patch
found 41721 27.0.50
quit

Platon Pronko <platon7pronko@gmail.com> writes:

> 1. 'emacs -Q'
> 2. 'M-x list-packages'
> 3. 'f'
> 4. Observe message "f is undefined"

This is because Emacs 27 introduced new filtering commands under the '/'
prefix, so the old binding 'f' no longer exists:

Filter packages by name in list-packages. (Bug#36981)
f96b8fd27c 2019-10-08 19:24:12 +0200
https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=f96b8fd27c382a941c52c2938544b9b0e3a2fb0e

Here's the relevant etc/NEWS entry:

  *** New functions for filtering packages list.
  A new function has been added which allows users to filter the
  packages list by name: 'package-menu-filter-by-name'.  By default, it
  is bound to '/ n'.  Additionally, the function
  'package-menu-filter-by-keyword' has been renamed from
  'package-menu-filter'.  Its keybinding has also been changed to '/ k'
  (from 'f').  To clear any of the two filters, the user can now call
  the 'package-menu-clear-filter' function, bound to '/ /' by default.

> When I type "h", in the help popup "f" is reserved to mean
> "filter". Online documentation also mentions only "f" to filter the
> packages:
> https://www.gnu.org/software/emacs/manual/html_node/emacs/Package-Menu.html

The online manual has not yet been updated because Emacs 27 is still at
the pretest stage and not officially released.

> In describe-mode I see that filtering is done using "/" prefix key, not with 
> "f".

Indeed.

The problem with 'h' (package-menu-quick-help) is that it is both
overengineered and limited in what it can do.  What it does is take a
word such as 'filter' and highlight a single character to indicate the
corresponding key binding.  E.g. ("filter" . 1) would highlight the 'i',
and "/-filter" would highlight the '/'.  This naively assumes that the
key binding is a single character, which is no longer the case.

On emacs-27, I propose we either remove the mention of filtering from
the quick help altogether, or write "/-filter" and let the user figure
out that '/' is actually a prefix that can be inspected in the usual
ways, such as by following it with C-h or <f1>.  For example:

>From 2525ae19d7154abda896f0d2cad2fd57ee3e5c8c Mon Sep 17 00:00:00 2001
From: "Basil L. Contovounesios" <contovob@tcd.ie>
Date: Fri, 5 Jun 2020 14:02:41 +0100
Subject: [PATCH] Update package-menu-quick-help

* lisp/emacs-lisp/package.el (package--quick-help-keys): Filtering
is now bound to the prefix '/', not the key 'f' (bug#41721).
Advertise only the standard 'g' binding now that both it and 'r' are
bound to revert-buffer (bug#35504).
(package--prettify-quick-help-key): Avoid modifying string literals.
(package-menu-filter): Reintroduce as obsolete alias of
package-menu-filter-by-keyword for backward
compatibility (bug#36981).
---
 lisp/emacs-lisp/package.el | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/lisp/emacs-lisp/package.el b/lisp/emacs-lisp/package.el
index 7af40247f3..7d6be3cf4e 100644
--- a/lisp/emacs-lisp/package.el
+++ b/lisp/emacs-lisp/package.el
@@ -3279,7 +3279,7 @@ package--quick-help-keys
   '(("install," "delete," "unmark," ("execute" . 1))
     ("next," "previous")
     ("Hide-package," "(-toggle-hidden")
-    ("refresh-contents," "g-redisplay," "filter," "help")))
+    ("g-refresh-contents," "/-filter," "help")))
 
 (defun package--prettify-quick-help-key (desc)
   "Prettify DESC to be displayed as a help menu."
@@ -3287,7 +3287,7 @@ package--prettify-quick-help-key
       (if (listp (cdr desc))
           (mapconcat #'package--prettify-quick-help-key desc "   ")
         (let ((place (cdr desc))
-              (out (car desc)))
+              (out (copy-sequence (car desc))))
           (add-text-properties place (1+ place)
                                '(face (bold font-lock-warning-face))
                                out)
@@ -3719,6 +3719,9 @@ package-menu-filter-by-keyword
                                    (list keyword)
                                  keyword)))
 
+(define-obsolete-function-alias
+  'package-menu-filter #'package-menu-filter-by-keyword "27.1")
+
 (defun package-menu-filter-by-name (name)
   "Filter the \"*Packages*\" buffer by NAME.
 Show only those items whose name matches the regular expression
-- 
2.26.2

On master, we could change package-menu-quick-help to support arbitrary
key bindings.

WDYT?

-- 
Basil