Bazel Mode is a GNU Emacs major mode for editing Bazel BUILD, WORKSPACE, and bzl files, which are written in the Starlark language.

To use Bazel Mode, add the following to your .emacs file after replacing "/path/to/bazel-mode/directory" with the location where you installed Bazel Mode:

(add-to-list 'load-path "/path/to/bazel-mode/directory")
(autoload 'bazel-mode "bazel-mode" "Major mode for Bazel BUILD files." t)
(add-to-list 'auto-mode-alist '("/BUILD\\(\\..*\\)?\\'" . bazel-mode))
(add-to-list 'auto-mode-alist '("/WORKSPACE\\'" . bazel-mode))
(add-to-list 'auto-mode-alist '("\\.\\(BUILD\\|WORKSPACE\\|bzl\\)\\'" . bazel-mode))

Bazel Mode supports reformatting BUILD files with buildifier. To use this feature, you'll need to download and install buildifier, which is part of Google's buildtools package:

git clone https://github.com/bazelbuild/buildtools.git
cd buildtools
bazel build //buildifier

and then install buildifier in some directory that's in your PATH shell environment variable.

Once buildifier is installed, you can use it in two different ways. First, Bazel Mode supports reformatting BUILD buffers by running bazel-format, which is bound to the key sequence C-c C-f. Additionally, you can configure Emacs to automatically format files with buildifier before saving them by adding the following to your .emacs file:

(add-hook 'bazel-mode-hook
          (lambda ()
            (add-hook 'before-save-hook #'bazel-format nil t)))