search

minad / affe

:monkey: affe.el - Asynchronous Fuzzy Finder for Emacs
GNU General Public License v3.0
225 stars 9 forks source link

readme

+title: affe.el - Asynchronous Fuzzy Finder for Emacs

+author: Daniel Mendler

+language: en

+export_file_name: affe.texi

+texinfo_dir_category: Emacs misc features

+texinfo_dir_title: Affe: (affe).

+texinfo_dir_desc: Asynchronous Fuzzy Finder for Emacs.

+html: GNU Emacs

+html: MELPA

+html: MELPA Stable

+html:

This package provides an asynchronous fuzzy finder similar to the [[https://github.com/junegunn/fzf][fzf command-line fuzzy finder]], written in pure Elisp. A producer process is started in the background, e.g., ~find~ or ~grep~. The output produced by this process is filtered by an external asynchronous Emacs process. The Emacs UI always stays responsive since the work is off-loaded to other processes. The results are presented in the minibuffer using [[https://github.com/minad/consult][Consult]], which allows to quickly select from the available items. Note that Affe is an experimental package and a demonstrator of asynchronous processing outside of Emacs in a separate process. Generally I recommend to use =consult-grep= or =consult-ripgrep=, since these commands will perform better for large projects. The Consult package itself is more mature.

+toc: headlines 8

The package is available on MELPA and can be installed using the Emacs package manager. If files should not be automatically previewed, a manual preview key should be set for ~affe-grep~.

+begin_src emacs-lisp

(use-package affe :config ;; Manual preview key for `affe-grep' (consult-customize affe-grep :preview-key "M-."))

+end_src

The default regular expression transformation of Consult is limited. It is recommended to configure [[https://github.com/oantolin/orderless][Orderless]] as =affe-regexp-compiler= in Consult.

+begin_src emacs-lisp

(defun affe-orderless-regexp-compiler (input _type _ignorecase) (setq input (cdr (orderless-compile input))) (cons input (apply-partially #'orderless--highlight input t))) (setq affe-regexp-compiler #'affe-orderless-regexp-compiler)

+end_src

Affe requires the ~rg~ ("ripgrep") command line program to be available. The producer processes can be customized by adjusting the variables ~affe-find-command~ and ~affe-grep-command~.

Affe depends on Consult and works best with the Vertico and the Mct completion UIs.

The Affe frontend transforms the input string to a list of regular expressions by calling the ~affe-regexp-function~. The regular expressions are passed to the Affe backend via the ~emacsclient~ protocol. The backend controls a producer process, which generates lines of text. The lines are filtered using the regular expressions submitted by the frontend. For performance reasons, ~all-completions~ is used for the filtering. The backend returns only a limited amount of matching candidates, hopefully the most plausible ones. The frontend calls the ~affe-highlight-function~ on the returned matches, to highlight the input pattern.

Affe uses a more primitive matching technique than ~fzf~, which uses the [[https://en.wikipedia.org/wiki/Smith%E2%80%93Waterman_algorithm][Smith-Waterman algorithm]]. Affe does not perform any ranking or sorting; it matches the lines in the order returned by the producer process against a list of regular expressions. On the upside, this allows plugging Affe together with the [[https://github.com/oantolin/orderless][Orderless]] completion style, which can give a consistent fuzzy filtering experience across all Emacs commands, including synchronous and asynchronous commands.

As possible enhancement of Affe, one could implement alphabetical and sorting by length in the backend. By using a bucket sorting technique the sorting complexity will stay sufficiently linear such that the performance impact should be acceptable. However implementing a scoring-based sorting is probably not feasible since this requires heavier computations in Elisp. But maybe nativecomp Emacs is a game changer here?