Some result candidates do not appear when using flx-rs

[Eason0210]

@jojojames and @jcs090218

When using the default backend flx, everthing is working well, but when the number of candidates is large (such as 10000 and more), it is slow. So I tried to use the faster backend flx-rs.

But Some result candidates do not appear when using flx-rs with M-x consult-imenu or M-x consult-line .

steps to reprodue:

1. create and empty file ~/.emacs.d/init.el
2. put the below minimal code in the init.el file

;;; init.el --- user-init-file                    -*- lexical-binding: t -*-

(require 'package)
(add-to-list 'package-archives '("melpa" . "https://melpa.org/packages/"))

(package-initialize)
(package-refresh-contents)

(eval-and-compile
  (setq use-package-enable-imenu-support t)
  (setq use-package-expand-minimally t)
    (require  'use-package))

(use-package flx-rs
  :load-path "~/src/packages/flx-rs/"
  :config
  (setq fussy-score-fn 'fussy-flx-rs-score)
  (flx-rs-load-dyn))

(use-package fussy
  :ensure t
  :custom
  (completion-styles '(fussy basic))
  (completion-category-defaults nil)
  (completion-category-overrides '((file (styles basic partial-completion))
                                   (eglot (styles fussy basic))))
  (fussy-score-fn 'fussy-flx-rs-score)
  (fussy-filter-fn 'fussy-filter-default)
  (fussy-use-cache t)
  :config
  (advice-add 'corfu--capf-wrapper :before 'fussy-wipe-cache)
  (add-hook 'corfu-mode-hook
            (lambda ()
              (setq-local fussy-max-candidate-limit 5000
                          fussy-default-regex-fn 'fussy-pattern-first-letter
                          fussy-prefer-prefix nil))))

(use-package vertico
  :ensure t
  :demand t
  :bind (:map vertico-map
              ([tab] . vertico-next)
              ([backtab] . vertico-previous))
  :custom (vertico-cycle t)
  :config (vertico-mode))

;; Example configuration for Consult
(use-package consult
  :ensure t
  :bind (;; C-c bindings in `mode-specific-map'
         ("C-c M-x" . consult-mode-command)
         ("C-c h" . consult-history)
         ("C-c k" . consult-kmacro)
         ("C-c m" . consult-man)
         ("C-c i" . consult-info)
         ([remap Info-search] . consult-info)
         ;; C-x bindings in `ctl-x-map'
         ("C-x M-:" . consult-complex-command)     ;; orig. repeat-complex-command
         ("C-x b" . consult-buffer)                ;; orig. switch-to-buffer
         ("C-x 4 b" . consult-buffer-other-window) ;; orig. switch-to-buffer-other-window
         ("C-x 5 b" . consult-buffer-other-frame)  ;; orig. switch-to-buffer-other-frame
         ("C-x t b" . consult-buffer-other-tab)    ;; orig. switch-to-buffer-other-tab
         ("C-x r b" . consult-bookmark)            ;; orig. bookmark-jump
         ("C-x p b" . consult-project-buffer)      ;; orig. project-switch-to-buffer
         ;; Custom M-# bindings for fast register access
         ("M-#" . consult-register-load)
         ("M-'" . consult-register-store)          ;; orig. abbrev-prefix-mark (unrelated)
         ("C-M-#" . consult-register)
         ;; Other custom bindings
         ("M-y" . consult-yank-pop)                ;; orig. yank-pop
         ;; M-g bindings in `goto-map'
         ("M-g e" . consult-compile-error)
         ("M-g f" . consult-flymake)               ;; Alternative: consult-flycheck
         ("M-g g" . consult-goto-line)             ;; orig. goto-line
         ("M-g M-g" . consult-goto-line)           ;; orig. goto-line
         ("M-g o" . consult-outline)               ;; Alternative: consult-org-heading
         ("M-g m" . consult-mark)
         ("M-g k" . consult-global-mark)
         ("M-g i" . consult-imenu)
         ("M-g I" . consult-imenu-multi)
         ;; M-s bindings in `search-map'
         ("M-s d" . consult-find)                  ;; Alternative: consult-fd
         ("M-s c" . consult-locate)
         ("M-s g" . consult-grep)
         ("M-s G" . consult-git-grep)
         ("M-s r" . consult-ripgrep)
         ("M-s l" . consult-line)
         ("M-s L" . consult-line-multi)
         ("M-s k" . consult-keep-lines)
         ("M-s u" . consult-focus-lines))

3. clone flx-rs to ~/src/packages/

git clone https://github.com/jcs-elpa/flx-rs.git ~/src/packages/flx-rs

4. start Emacs，it will install the related packages
5. open the init.el file by C-x C-f ~/.emacs.d/init.el
6. M-x consult-imenu you will see all the candidates as below, so far so good.

7. Then you type a character c in the minibuffer prompt, you will get no candiates. This is the issue.

if I disable the flx-rs and use flx, the result is as below:
I don't known why the "fussy" can match the c??

when input co, the result is expected:

[jcs090218]

I can reproduce this bug. I will need to dig into the source code to figure out this bug. 🤔 Thanks for the detailed steps to reproduce this bug!

Edit: How to reproduce this bug with Eask: (for future references)

# Create test project and navigate to the created project
$ mkdir test-fussy && cd test-fussy

# Create Eask-file (leave everything answers empty since it doesn't matter)
$ eask init

# Add sources
$ eask source add melpa      # For everything else
$ eask source add jcs-elpa   # For `flx-rs`

# Installed used packages/dependencies
$ eask install consult flx flx-rs fussy vertico

Then paste the above config to ./.eask/<emacs-version>/init.el

$ eask emacs  # Start Emacs with those packages installed

[oscarfv]

@jcs090218 : is this issue related to flx-rs?

I'm seeing a similar case, but it happens when using vertico + fussy + (flx-rs or plain flx). With ido + flx-ido + flx-rs there is no problem. So it seems that the culprit is not flx-rs itself.

[jcs090218]

I recently updated the flx-rs; maybe that solves the issue. 🤔 @Eason0210 Can you try with the latest version?

[Eason0210]

@jcs090218 I tried the latest commit of flx-rs, but the issue is still exist.

[oscarfv]

@jcs090218 : on the issue I've observed there is no difference from the current release of flx-rs to the previous one.

[oscarfv]

Upon further investigation, it seems that I'm misunderstanding what the fussy/emacs combo does.

I have

(setq completion-styles '(fussy))

When switching buffers with vertico (C-x b) as long as the input corresponds to the substring of some candidate, fussy-score is not invoked. Only when the input does not match any candidate as substring, fussy-score is invoked.

For instance, let's say I have these three buffers: parser.cpp parser.h prelude.cpp do-process.cpp. If the input is p, only those that start with that letter are listed, do-process.cpp is excluded. If the input is pr, only prelude.cpp is listed. If then the input is prc, then fussy-score is invoked and all the candidates are listed again.

I find this behavior very confusing. I've looked for some configuration that controls this, but found none. What I'm missing?

It seems that only happens in switch-buffer.

(I also realize that my problem is not the same as the the OP, so apologies to @Eason0210 for hijacking his report.)