corfu--recompute: Preserve selected candidate on further input

1 files changed, 18 insertions, 14 deletions

diff --git a/corfu.el b/corfu.el
index 97f47fe..637ef6b 100644
--- a/corfu.el
+++ b/corfu.el
@@ -643,7 +643,8 @@ FRAME is the existing frame."
                (completing-file (eq (corfu--metadata-get 'category) 'file))
                (`(,all . ,hl) (corfu--filter-completions str table pred pt corfu--metadata))
                (base (or (when-let ((z (last all))) (prog1 (cdr z) (setcdr z nil))) 0))
-               (corfu--base (substring str 0 base)))
+               (corfu--base (substring str 0 base))
+               (pre nil))
     ;; Filter the ignored file extensions. We cannot use modified predicate for
     ;; this filtering, since this breaks the special casing in the
     ;; `completion-file-name-table' for `file-exists-p' and `file-directory-p'.
@@ -661,21 +662,25 @@ FRAME is the existing frame."
           all (corfu--move-prefix-candidates-to-front field all))
     (when (and completing-file (not (string-suffix-p "/" field)))
       (setq all (corfu--move-to-front (concat field "/") all)))
-    (setq all (corfu--move-to-front field all))
+    (setq all (corfu--move-to-front field all)
+          pre (if (or (eq corfu-preselect 'prompt) (not all)
+                      (and completing-file (eq corfu-preselect 'directory)
+                           (= (length corfu--base) (length str))
+                           (test-completion str table pred))
+                      (and (eq corfu-preselect 'valid)
+                           (not (equal field (car all)))
+                           (not (and completing-file (equal (concat field "/") (car all))))
+                           (test-completion str table pred)))
+                  -1 0))
     `((corfu--base . ,corfu--base)
       (corfu--metadata . ,corfu--metadata)
       (corfu--candidates . ,all)
       (corfu--total . ,(length all))
       (corfu--hilit . ,(or hl #'identity))
-      (corfu--preselect . ,(if (or (eq corfu-preselect 'prompt) (not all)
-                                   (and completing-file (eq corfu-preselect 'directory)
-                                        (= (length corfu--base) (length str))
-                                        (test-completion str table pred))
-                                   (and (eq corfu-preselect 'valid)
-                                        (not (equal field (car all)))
-                                        (not (and completing-file (equal (concat field "/") (car all))))
-                                        (test-completion str table pred)))
-                               -1 0)))))
+      (corfu--preselect . ,pre)
+      (corfu--index . ,(or (and (>= corfu--index 0) (/= corfu--index corfu--preselect)
+                                (seq-position all (nth corfu--index corfu--candidates)))
+                           pre)))))
 
 (defun corfu--update (&optional interruptible)
   "Update state, optionally INTERRUPTIBLE."
@@ -702,9 +707,8 @@ FRAME is the existing frame."
                   t)))
         ('nil (keyboard-quit))
         ((and state (pred consp))
-         (dolist (s state) (set (car s) (cdr s)))
-         (setq corfu--input input
-               corfu--index corfu--preselect))))
+         (setq corfu--input input)
+         (dolist (s state) (set (car s) (cdr s))))))
     input))
 
 (defun corfu--match-symbol-p (pattern sym)