Score flex-style completions according to match tightnessscratch/new-flex-completion-style

The new completion style needs to score completion matches so that we
can use it later on when sorting the completions.  This is because, in
the flex style, "foo" can now match "foobar", "frodo" and
"barfromsober" but we probably want "foobar" to appear at the top of
the completion list.

This change makes the new flex completion style add sort-order hints
under the completion string's `completion-style-sort-order' property.

* lisp/minibuffer.el (completion-pcm--hilit-commonality): Propertize
completion with 'completion-pcm-commonality-score.
(completion-flx-all-completions): Propertize completion with
completion-style-sort-order and completion-style-annotation.

1 files changed, 30 insertions, 7 deletions

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index cf626b3f32d..8ea70b14f12 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -3056,20 +3056,38 @@ PATTERN is as returned by `completion-pcm--string->pattern'."
          (let* ((pos (if point-idx (match-beginning point-idx) (match-end 0)))
                 (md (match-data))
                 (start (pop md))
-                (end (pop md)))
+                (end (pop md))
+                (len (length str))
+                (score-numerator 0)
+                (score-denominator 0)
+                (aux 0)
+                (update-score
+                 (lambda (a b)
+                   "Update score variables given match range (A B)."
+                   (setq
+                    score-numerator   (+ score-numerator (- b a))
+                    score-denominator (+ score-denominator (expt (- a aux) 1.5))
+                    aux              b))))
+           (funcall update-score 0 start)
            (while md
-             (put-text-property start (pop md)
+             (funcall update-score start (car md))
+             (put-text-property start
+                                (pop md)
                                 'font-lock-face 'completions-common-part
                                 str)
              (setq start (pop md)))
            (put-text-property start end
                               'font-lock-face 'completions-common-part
                               str)
+           (funcall update-score start end)
            (if (> (length str) pos)
                (put-text-property pos (1+ pos)
-                                  'font-lock-face 'completions-first-difference
-                                  str)))
-         str)
+                                  'font-lock-face 'completions-first-difference
+                                  str))
+           (put-text-property
+            0 1 'completion-pcm-commonality-score
+            (/ score-numerator (* len (1+ score-denominator)) 1.0) str))
+         str)
        completions))))
 
 (defun completion-pcm--find-all-completions (string table pred point
@@ -3440,8 +3458,13 @@ which is at the core of flex logic.  The extra
                 string table pred point
                 #'completion-flex--make-flex-pattern)))
     (when all
-      (nconc (completion-pcm--hilit-commonality pattern all)
-             (length prefix)))))
+      (let ((hilighted (completion-pcm--hilit-commonality pattern all)))
+        (mapc
+         (lambda (comp)
+           (let ((score (get-text-property 0 'completion-pcm-commonality-score comp)))
+             (put-text-property 0 1 'completion-style-sort-order (- score) comp)))
+         hilighted)
+        (nconc hilighted (length prefix))))))
 
 ;; Initials completion
 ;; Complete /ums to /usr/monnier/src or lch to list-command-history.