Clojure Mode

Provides Emacs font-lock, indentation, and navigation for the Clojure programming language.

More thorough walkthroughs are available at clojure-doc.org and Clojure for the Brave and the True.

Installation

Available on all major package.el community maintained repos - MELPA Stable, MELPA and Marmalade repos.

MELPA Stable and Marmalade are recommended as they have the latest stable version. MELPA has a development snapshot for users who don't mind breakage but don't want to run from a git checkout.

You can install clojure-mode using the following command:

M-x package-install [RET] clojure-mode [RET]

or if you'd rather keep it in your dotfiles:

(unless (package-installed-p 'clojure-mode)
  (package-install 'clojure-mode))

If the installation doesn't work try refreshing the package list:

M-x package-refresh-contents

Extra font-locking

Prior to version 3.0 clojure-mode bundled unreliable font-locking for some built-in vars. In 3.0 this was extracted from clojure-mode and moved to a separate package - clojure-mode-extra-font-locking.

Configuration

To see a list of available configuration options do M-x customize-group RET clojure.

Indentation options

The default indentation rules in clojure-mode are derived from the community Clojure Style Guide. Please, refer to the guide for the general Clojure indentation rules.

The indentation of special forms and macros with bodies is controlled via put-clojure-indent, define-clojure-indent and clojure-backtracking-indent. Nearly all special forms and built-in macros with bodies have special indentation settings in clojure-mode. You can add/alter the indentation settings in your personal config. Let's assume you want to indent ->> and -> like this:

(->> something
  ala
  bala
  portokala)

You can do so by putting the following in your config:

(put-clojure-indent '-> 1)
(put-clojure-indent '->> 1)

You can also specify different indentation settings for symbols prefixed with some ns (or ns alias):

(put-clojure-indent 'do 0)
(put-clojure-indent 'my-ns/do 1)

This means that the body of the ->/->> is after the first argument.

A more compact way to do the same thing is:

(define-clojure-indent
  (-> 1)
  (->> 1))

The bodies of certain more complicated macros and special forms (e.g. letfn, deftype, extend-protocol, etc) are indented using a contextual backtracking indentation method, controlled by clojure-backtracking-indent. Here's some example config code:

(put 'implement 'clojure-backtracking-indent '(4 (2)))
(put 'letfn 'clojure-backtracking-indent '((2) 2))
(put 'proxy 'clojure-backtracking-indent '(4 4 (2)))
(put 'reify 'clojure-backtracking-indent '((2)))
(put 'deftype 'clojure-backtracking-indent '(4 4 (2)))
(put 'defrecord 'clojure-backtracking-indent '(4 4 (2)))
(put 'defprotocol 'clojure-backtracking-indent '(4 (2)))
(put 'extend-type 'clojure-backtracking-indent '(4 (2)))
(put 'extend-protocol 'clojure-backtracking-indent '(4 (2)))
(put 'specify 'clojure-backtracking-indent '(4 (2)))
(put 'specify! 'clojure-backtracking-indent '(4 (2)))

Don't use special indentation settings for forms with names that are not unique, as clojure-mode's indentation engine is not namespace-aware and you might end up getting strange indentation in unexpected places.

Please, see the docstrings of the Emacs Lisp functions/vars noted above for information about customizing this indentation behavior.

Related packages

• clojure-mode-extra-font-locking provides additional font-locking for built-in methods and macros. The font-locking is pretty imprecise, because it doesn't take namespaces into account and it won't font-lock a function at all possible positions in a sexp, but if you don't mind its imperfections you can easily enable it:

(require 'clojure-mode-extra-font-locking)

The code in clojure-mode-font-locking used to be bundled with clojure-mode before version 3.0.

You can also use the code in this package as a basis for extending the font-locking further (e.g. functions/macros from more namespaces). Generally you should avoid adding special font-locking for things that don't have fairly unique names, as this will result in plenty of incorrect font-locking.

• clj-refactor provides refactoring support.

• Enabling CamelCase support for editing commands(like forward-word, backward-word, etc) in clojure-mode is quite useful since we often have to deal with Java class and method names. The built-in Emacs minor mode subword-mode provides such functionality:

(add-hook 'clojure-mode-hook #'subword-mode)

• The use of paredit when editing Clojure (or any other Lisp) code is highly recommended. It helps ensure the structure of your forms is not compromised and offers a number of operations that work on code structure at a higher level than just characters and words. To enable it for Clojure buffers:

(add-hook 'clojure-mode-hook #'paredit-mode)

• smartparens is an excellent (newer) alternative to paredit. Many Clojure hackers have adopted it recently and you might want to give it a try as well. To enable smartparens use the following code:

(add-hook 'clojure-mode-hook #'smartparens-strict-mode)

• RainbowDelimiters is a minor mode which highlights parentheses, brackets, and braces according to their depth. Each successive level is highlighted in a different color. This makes it easy to spot matching delimiters, orient yourself in the code, and tell which statements are at a given depth. Assuming you've already installed RainbowDelimiters you can enable it like this:

(add-hook 'clojure-mode-hook #'rainbow-delimiters-mode)

REPL Interaction

A number of options exist for connecting to a running Clojure process and evaluating code interactively.

Basic REPL

Install inf-clojure for basic interaction with a REPL process.

CIDER

You can also use Leiningen to start an enhanced REPL via CIDER.

Changelog

An extensive changelog is available here.

License

Copyright © 2007-2015 Jeffrey Chu, Lennart Staflin, Phil Hagelberg, Bozhidar Batsov and contributors.

Distributed under the GNU General Public License; type C-h C-c to view it.