Clojure Mode

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

A more thorough walkthrough is available at clojure-doc.org.

Installation

Available on both MELPA Stable and MELPA repos.

MELPA Stable is recommended as it has the latest stable version, but MELPA has a development snapshot for users who don't mind breakage but don't want to run from a git checkout.

If you're not already using MELPA Stable, add this to your ~/.emacs.d/init.el and load it with M-x eval-buffer.

(require 'package)
(add-to-list 'package-archives
             '("melpa-stable" . "http://melpa-stable.milkbox.net/packages/"))
(package-initialize)

If you're feeling adventurous and you'd like to use MELPA add this bit of code instead:

(require 'package)
(add-to-list 'package-archives
             '("melpa" . "http://melpa.milkbox.net/packages/") t)
(package-initialize)

And then you can install:

M-x package-refresh-contents

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)
  (package-install 'clojure-mode))

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

Characterizing the default indentation rules of clojure-mode 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. case, 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

Use M-x run-lisp to open a simple REPL subprocess using Leiningen. Once that has opened, you can use C-c C-r to evaluate the region or C-c C-l to load the whole file.

If you don't use Leiningen, you can set inferior-lisp-program to a different REPL command.

CIDER

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

Swank Clojure

SLIME is available via swank-clojure in clojure-mode 1.x. SLIME support was removed in version 2.x in favor of CIDER.

Clojure Test Mode

Deprecated

This source repository also includes clojure-test-mode.el, which provides support for running Clojure tests (using the clojure.test framework) via CIDER and seeing feedback in the test buffer about which tests failed or errored. The installation instructions above should work for clojure-test-mode as well.

Once you have a repl session active, you can run the tests in the current buffer with C-c C-,. Failing tests and errors will be highlighted using overlays. To clear the overlays, use C-c k.

The mode is deprecated (more details here) and will not be improved/maintained anymore. All clojure-test-mode users should start using CIDER 0.7+, which features built-in support for clojure.test.

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.