master ba85251: Don't mess up grouping in completion-all-sorted-completions

[João Távora]

branch: master
commit ba852512f23fdab674086e35d4207e3970dd0912
Author: João Távora <joaotavora@gmail.com>
Commit: João Távora <joaotavora@gmail.com>

    Don't mess up grouping in completion-all-sorted-completions
    
    The default sorting order will mess up the naturally grouped order of
    the candidates in the table that specified the group-function.
    
    As seen in xref.el when
    
       (setq xref-show-definitions-function
             'xref-show-definitions-completing-read)
       (setq completions-group t)
       M-x fido-mode
    
    Also partially seen with C-x 8 RET (M-x insert-char) with
    
       (setq read-char-by-name-sort 'code)
    
    bug#48545
    
    * lisp/minibuffer.el (completion-all-sorted-completions): Don't
    use default sort if there's a group-function in the table.
---
 lisp/minibuffer.el | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index ffcd5d8..89d3a2a 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -1496,7 +1496,8 @@ Remove completion BASE prefix string from history 
elements."
                                            base-size md
                                            minibuffer-completion-table
                                            minibuffer-completion-predicate))
-             (sort-fun (completion-metadata-get all-md 'cycle-sort-function)))
+             (sort-fun (completion-metadata-get all-md 'cycle-sort-function))
+             (group-fun (completion-metadata-get all-md 'group-function)))
         (when last
           (setcdr last nil)
 
@@ -1506,17 +1507,25 @@ Remove completion BASE prefix string from history 
elements."
           (setq all (delete-dups all))
           (setq last (last all))
 
-          (if sort-fun
-              (setq all (funcall sort-fun all))
-            ;; Sort first by length and alphabetically.
+          (cond
+           (sort-fun (setq all (funcall sort-fun all)))
+           ((and completions-group group-fun)
+            ;; TODO: experiment with re-grouping here.  Might be slow
+            ;; if the group-fun (given by the table and out of our
+            ;; control) is slow and/or allocates too much.
+            )
+           (t
+            ;; If the table doesn't stipulate a sorting function or a
+            ;; group function, sort first by length and
+            ;; alphabetically.
             (setq all (minibuffer--sort-by-length-alpha all))
-            ;; Sort by history position, put the default, if it
+            ;; Then sort by history position, and put the default, if it
             ;; exists, on top.
             (when (minibufferp)
               (setq all (minibuffer--sort-by-position
                          (minibuffer--sort-preprocess-history
                           (substring string 0 base-size))
-                         all))))
+                         all)))))
 
           ;; Cache the result.  This is not just for speed, but also so that
           ;; repeated calls to minibuffer-force-complete can cycle through