biomejs-format.el

biomejs-format is a function that formats the current buffer using Biome. The package also exports a minor mode that applies (biomejs-format) on save.

This is forked from https://github.com/prettier/prettier-emacs and made for users who switched from Prettier to Biome, to replace that easily.

Configuration

Requirements

Ensure that the biome program is installed:

which biome

If biome is not installed already, please refer https://biomejs.dev/guides/getting-started/#installation .

Basic configuration

First require the package:

(require 'biomejs-format)

Then you can hook to your favorite javascript mode:

(add-hook 'js2-mode-hook 'biomejs-format-mode)
(add-hook 'web-mode-hook 'biomejs-format-mode)
...

Biome arguments

To adjust the CLI args used for the biome command, you can customize the biomejs-format-biome-args variable:

(setq biomejs-format-biome-args '(
  "format"
  "--trailing-comma" "all"
  "--bracket-spacing" "false"
))

Usage with web-mode

Web-mode is a popular mode for editing .js and .jsx files, but it is used to edit other template files too. If you want to hook biomejs-format to web-mode for .js and .jsx files only, you can define a helper function like this:

(defun enable-minor-mode (my-pair)
  "Enable minor mode if filename match the regexp.  MY-PAIR is a cons cell (regexp . minor-mode)."
  (if (buffer-file-name)
      (if (string-match (car my-pair) buffer-file-name)
      (funcall (cdr my-pair)))))

And then hook to web-mode like this:

(add-hook 'web-mode-hook #'(lambda ()
                            (enable-minor-mode
                             '("\\.jsx?\\'" . biomejs-format-mode))))

Installing on Windows

This package requires the diff tool which is already included on Unix platforms. The simplest way to install diff on Windows is to use Chocolatey. The steps are as follows:

1. Follow the Chocolatey install instructions: https://chocolatey.org/install
2. Open an Admin Powershell session
3. Install the diff program: choco install diffutils

You should now be able to open Emacs and successfully use this package.

Customization

This package is customizable via custom.el:

M-x customize-group biomejs-format

• biomejs-format-biome-command is the biome command
• biomejs-format-biome-args are the args passed to the biome command
• biomejs-format-show-errors customizes where to display the error output (buffer, echo or nil)
• biomejs-format-width-mode customizes the width when formatting buffer contents (window, fill or nil)

Using node_modules/.bin/biome

If you want to use your project's biome version you can rely on https://github.com/codesuki/add-node-modules-path

(eval-after-load 'web-mode
    '(progn
       (add-hook 'web-mode-hook #'add-node-modules-path)
       (add-hook 'web-mode-hook #'biomejs-format-mode)))

See also

• https://github.com/cxa/lsp-biome provides integration for lsp-mode with more features.
• https://github.com/purcell/emacs-reformatter provides smarter way to define reformatters.