Swank Clojure is a server that allows SLIME (the Superior Lisp Interaction Mode for Emacs) to connect to Clojure projects.
The simplest way is to just "jack in" from an existing project using Leiningen:
clojure-modeeither from Marmalade or from git.
lein plugin install swank-clojure 1.4.0
- From an Emacs buffer inside a project, invoke
That's all it takes; there are no extra install steps beyond
clojure-mode on the Emacs side and the
swank-clojure plugin on the
Leiningen side. In particular be sure you don't have any other
versions of Slime installed; see "Troubleshooting" below.
Commonly-used SLIME commands:
- M-.: Jump to the definition of a var
- M-TAB or C-c TAB: Autocomplete symbol at point
- C-x C-e: Eval the form under the point
- C-c C-k: Compile the current buffer
- C-c C-l: Load current buffer and force required namespaces to reload
- C-M-x: Compile the whole top-level form under the point.
- C-c S-i: Inspect a value
- C-c C-m: Macroexpand the call under the point
- C-c C-d C-d: Look up documentation for a var
- C-c C-z: Switch from a Clojure buffer to the repl buffer
- C-c M-p: Switch the repl namespace to match the current buffer
- C-c C-w c: List all callers of a given function
Pressing "v" on a stack trace a debug buffer will jump to the file and line referenced by that frame if possible.
Note that SLIME was designed to work with Common Lisp, which has a
distinction between interpreted code and compiled code. Clojure has no
such distinction, so the load-file functionality is overloaded to add
There are other ways to use Swank for different specific circumstances. For each of these methods you will have to install the slime and slime-repl Emacs Lisp libraries manually as outlined in "Connecting with SLIME" below.
If you just want a standalone swank server with no third-party libraries, you can use the shell wrapper that Leiningen installs for you:
$ lein plugin install swank-clojure 1.4.0 $ ~/.lein/bin/swank-clojure M-x slime-connect
If you put
~/.lein/bin on your $PATH it's even more
Manual Swank in Project
You can also start a swank server by hand from inside your project.
You'll need to have installed using
lein plugin install, then launch the server from the shell:
$ lein swank # you can specify PORT and HOST optionally
If you're using Maven, add this to your pom.xml under the <dependencies> section:
<dependency> <groupId>swank-clojure</groupId> <artifactId>swank-clojure</artifactId> <version>1.3.4</version> </dependency>
Then you can launch a swank server like so:
$ mvn clojure:swank
Note that due to a bug in clojure-maven-plugin, you currently cannot include it as a test-scoped dependency; it must be compile-scoped. You also cannot change the port from Maven; it's hard-coded to 4005.
You can embed Swank Clojure in your project, start the server from within your own code, and connect via Emacs to that instance:
(ns my-app (:require [swank.swank])) (swank.swank/start-server) ;; optionally takes :host/:port keyword args
To make this work in production, swank-clojure needs to be in
:dependencies in project.clj in addition to being installed
as a user-level plugin. If you do this, you can also start the server
directly from the
java command-line launcher if you're using Clojure
1.3 or newer:
$ java -cp my-project-standalone-1.0.0.jar clojure.main -m swank.swank
Connecting with SLIME
If you're not using the
M-x clojure-jack-in method mentioned
above, you'll have to install SLIME yourself. The easiest way is to
use package.el. If you are using Emacs 24 or the
Emacs Starter Kit,
then you have it already. If not, get it
from Emacs's own repository.
Then add Marmalade as an archive source in your Emacs config:
(require 'package) (add-to-list 'package-archives '("marmalade" . "http://marmalade-repo.org/packages/") t) (package-initialize)
Evaluate that, then run M-x package-refresh-contents to pull in the latest source lists. Then you can do M-x package-install and choose slime-repl.
When you perform the installation, you will see warnings related to the byte-compilation of the packages. This is normal; the packages will work just fine even if there are problems byte-compiling it upon installation.
Then you should be able to connect to the swank server you launched:
It will prompt you for your host (usually localhost) and port. It may also warn you that your SLIME version doesn't match your Swank version; this should be OK.
To get syntax highlighting in your repl buffer, use this elisp:
(add-hook 'slime-repl-mode-hook (defun clojure-mode-slime-font-lock () (let (font-lock-mode) (clojure-mode-font-lock-setup))))
To get colors in stack traces, load the elisp in
src/swank/payload/slime-frame-colors.el inside Emacs and use
lein swank $PORT localhost :colors? true to launch the swank server.
Currently having multiple versions of swank-clojure on the classpath
can cause issues when running
lein swank or
lein jack-in. It's
recommended to not put swank-clojure in your
lein plugin install to have it installed globally for all
projects instead. This also means that people hacking on your project
won't have to pull it in if they are not Emacs users.
It's also possible for some packages to pull in old versions of
swank-clojure transitively, so check the
lib/ directory if
you are having issues. In particular, Incanter is known to exhibit
this problem. Judicious use of
:exclusions make it work:
:dependencies [[incanter "1.2.3" :exclusions [swank-clojure]]]
Since swank-clojure 1.3.4, having versions of clj-stacktrace older
than 0.2.1 in your project or user-level plugins will cause
Unable to resolve symbol: pst-elem-str errors. Keep in mind that user-level
~/.lein/plugins are uberjars in Leiningen 1.x, so it's
possible that one of your plugins (such as
version 1.3.7) contains an old clj-stacktrace even if it doesn't have
its own file there. Specifying a newer version should be enough if
you're having trouble:
:dependencies [[clj-stacktrace "0.2.4"]]
Having old versions of SLIME installed either manually or using a
system-wide package manager like apt-get may cause issues. Also the
official CVS version of SLIME is not supported; it often breaks
compatibility with Clojure. In addition, the
slime-clj packages are
incompatible with swank-clojure.
It's possible to have Emacs configured for both Common Lisp and Clojure if you defer loading of Slime until it's needed. This issue has details on how that is done. It's not possible to have a single instance of Emacs connect to both though.
Swank-clojure and SLIME are only tested with GNU Emacs; forks such as Aquamacs and XEmacs may work but are not officially supported.
On Mac OS X, Emacs sessions launched from the GUI don't always respect
your configured $PATH. If Emacs can't find
lein, you may need to
give it some help. The quickest way is probably to add this elisp to
(setenv "PATH" (shell-command-to-string "echo $PATH"))
clojure-jack-in, standard out for the Leiningen process
appears in the
*swank* buffer, but the
*out* var gets rebound to a
writer that is able to redirect to the
*slime-repl* buffer. So in
general most Clojure output will show up in your repl buffer just
fine, but for output coming from Java libraries you may need to check
If you are running Emacs from Cygwin, you'll need to add the following to your .emacs.d/init.el file:
(defun cyg-slime-to-lisp-translation (filename) (replace-regexp-in-string "\n" "" (shell-command-to-string (format "cygpath.exe --windows %s" filename)))) (defun cyg-lisp-to-slime-translation (filename) (replace-regexp-in-string "\n" "" (shell-command-to-string (format "cygpath.exe --unix %s filename")))) (setq slime-to-lisp-filename-function #'cyg-slime-to-lisp-translation) (setq lisp-to-slime-filename-function #'cyg-lisp-to-slime-translation)
This is required because the jvm runs as a normal Windows exe and uses Windows style paths rather than Cygwin unix style paths.
How it Works
Swank Clojure is simply a server that communicates over the Slime
protocol with an Emacs process. As such it runs in a JVM process,
usually launched by Leiningen. Slime is a client that runs within
Emacs to communicate with Swank. You can start the two of them
separately as explained in "Connecting with SLIME" above, but
M-x clojure-jack-in will send the elisp code for Slime to the Emacs
process to ensure that it uses a version of Slime that is compatible
with that version of Swank. Once the Swank server is finished loading,
it sends a signal to Emacs to connect to it.
You can set repl-aware breakpoints using
For now, see
Hugo Duncan's blog
for an explanation of this excellent feature.
CDT (included in Swank Clojure since 1.4.0) is a more comprehensive debugging tool that includes support for stepping, seting breakpoints, catching exceptions, and eval clojure expressions in the context of the current lexical scope.
Note that the CDT does not work with
extra manual configuration.
- unmap-ns command
- show method argument names in slime inspector (theoretically possible?)
- show better metadata on functions in inspector
- offer restarts for class/var not found exceptions (slamhound integration?)
- add elisp payload for cdt commands
- suppress false "warning: unabled to add tools.jar to classpath" message
The swank-clojure mailing list and clojure channel on Freenode are the best places to bring up questions/issues.
Contributions are preferred as either Github pull requests or using "git format-patch". Please use standard indentation with no tabs, trailing whitespace, or lines longer than 80 columns. See this post on submitting good patches for some tips. If you've got some time on your hands, reading this style guide wouldn't hurt either.
Copyright © 2008-2012 Jeffrey Chu, Phil Hagelberg, Hugo Duncan, and contributors
Licensed under the EPL. (See the file COPYING.)