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-refresh-contents))

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.

Characterizing them is difficult to do in summary; this is one attempt:

1. Bodies of parenthesized forms are indented such that arguments are aligned to the start column of the first argument, except for a class of forms identified by the symbol in function position, the bodies of which are indented two spaces, regardless of the position of their first argument (this is called "defun" indentation, for historical reasons):
2. Known special forms (e.g. loop, try, etc)
3. Nearly all "core" macros that ship as part of Clojure itself
4. Userland macros (and any other form?) that are locally registered via put-clojure-indent, define-clojure-indent (helpers for adding mappings to clojure-indent-function).
5. 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.
6. The bodies of other forms (e.g. vector, map, and set literals) are indented such that each new line within the form is set just inside of the opening delimiter of the form.

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

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 functions 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.

• clj-refactor provides simple 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 © 2007-2014 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.