bug#53362: 29.0.50; [PATCH] Make Completions sorting a user option

[Protesilaos Stavrou <info@protesilaos.com>]

[-- Attachment #1: Type: text/plain, Size: 353 bytes --]

Dear maintainers,

I was wondering whether we could make the sorting of candidates in the
Completions' buffer subject to a user option.

See the attached patch for a possible implementation.  I have kept it
backward-compatible by making string-lessp the default sort function.

All the best,
Protesilaos

-- 
Protesilaos Stavrou
https://protesilaos.com

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-Make-Completions-sorting-a-user-option.patch --]
[-- Type: text/x-patch, Size: 3078 bytes --]

From e53bd2b2383f3dfa367f2af8d4ed43c6c42dd002 Mon Sep 17 00:00:00 2001
Message-Id: <e53bd2b2383f3dfa367f2af8d4ed43c6c42dd002.1642595067.git.info@protesilaos.com>
From: Protesilaos Stavrou <info@protesilaos.com>
Date: Wed, 19 Jan 2022 14:20:19 +0200
Subject: [PATCH] Make Completions sorting a user option

* etc/NEWS: Document the new user option.
* lisp/minibuffer.el (completions-sort): Add new user option.
(minibuffer-completion-help): Implement it for the Completions buffer.
---
 etc/NEWS           |  6 ++++++
 lisp/minibuffer.el | 19 ++++++++++++++++++-
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/etc/NEWS b/etc/NEWS
index 47dbfba9c0..c2d442833c 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -418,6 +418,12 @@ When non-nil, the commands 'next-completion' and 'previous-completion'
 automatically wrap around on reaching the beginning or the end of
 the *Completions* buffer.
 
+*** New user option 'completions-sort'.
+Controls the sorting of the completion candidates in the *Completions*
+buffer.  Available styles are no sorting, alphabetical, lexicographic
+(the default), or a custom sort function.  The function takes and
+returns a list of completion candidate strings.
+
 ** Isearch and Replace
 
 +++
diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index ab760a42d1..d64b0cbd24 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -1169,6 +1169,20 @@ (defcustom completion-cycle-threshold nil
   :version "24.1"
   :type completion--cycling-threshold-type)
 
+(defcustom completions-sort 'lexicographic
+  "Sort candidates in the *Completions* buffer.
+
+The value can be nil to disable sorting altogether,
+`alphabetical' for alphabetical sorting, `lexicographic' for
+lexicographic sorting, or a custom sorting function.  The sorting
+function takes and returns a list of completion candidate
+strings."
+  :type '(choice (const :tag "No sorting" nil)
+                 (const :tag "Alphabetical sorting" alphabetical)
+                 (const :tag "Lexicographic sorting" lexicographic)
+                 function :tag "Custom function")
+  :version "29.1")
+
 (defcustom completions-group nil
   "Enable grouping of completion candidates in the *Completions* buffer.
 See also `completions-group-format' and `completions-group-sort'."
@@ -2264,7 +2278,10 @@ (defun minibuffer-completion-help (&optional start end)
                       ;; same, but not always.
                       (setq completions (if sort-fun
                                             (funcall sort-fun completions)
-                                          (sort completions 'string-lessp)))
+                                          (pcase completions-sort
+                                            ('alphabetical (sort completions #'string-version-lessp))
+                                            ('lexicographic (sort completions #'string-lessp))
+                                            (_ completions))))
 
                       ;; After sorting, group the candidates using the
                       ;; `group-function'.
-- 
2.34.1