Leiningen

"Leiningen!" he shouted. "You're insane! They're not creatures you can fight—they're an elemental—an 'act of God!' Ten miles long, two miles wide—ants, nothing but ants! And every single one of them a fiend from hell..."

from Leiningen Versus the Ants by Carl Stephenson

Leiningen is for automating Clojure projects without setting your hair on fire.

Installation

If your preferred package manager has a relatively recent version of Leiningen, try that first. Otherwise you can install by hand:

Leiningen bootstraps itself using the lein shell script; there is no separate install script. It installs its dependencies upon the first run on unix, so the first run will take longer.

Download the script.
Place it on your $PATH. (I like to use ~/bin)
Set it to be executable. (chmod 755 ~/bin/lein)

The link above will get you the 2.x preview release. There is still a lot of extant material on the Web concerning the older Leiningen 1.x version, which is still available if you need to work on older projects that aren't compatible with 2.x yet. The upgrade guide has instructions on migrating to version 2.

On Windows most users can get the batch file. If you have wget.exe or curl.exe already installed and in PATH, you can just run lein self-install, otherwise get the standalone jar from the downloads page. If you have Cygwin you should be able to use the shell script above rather than the batch file.

Basic Usage

The tutorial has a detailed walk-through of the steps involved in creating a new project, but here are the commonly-used tasks:

$ lein new [TEMPLATE] NAME # generate a new project skeleton

$ lein test [TESTS] # run the tests in the TESTS namespaces, or all tests

$ lein repl # launch an interactive REPL session

$ lein run -m my.namespace # run the -main function of a namespace

$ lein uberjar # package the project and dependencies as standalone jar

Use lein help to see a complete list. lein help $TASK shows the usage for a specific task.

You can also chain tasks together in a single command by using the do task with comma-separated tasks:

$ lein do clean, test foo.test-core, jar

Most tasks need to be run from somewhere inside a project directory to work, but some (new, help, search, version, and repl) may run from anywhere.

Configuration

The project.clj file in the project root should look like this:

(defproject myproject "0.5.0-SNAPSHOT"
  :description "A project for doing things."
  :url "http://github.com/technomancy/myproject"
  :dependencies [[org.clojure/clojure "1.4.0"]]
  :plugins [[lein-ring "0.4.5"]])

The lein new task generates a project skeleton with an appropriate starting point from which you can work. See the sample.project.clj file (also available via lein help sample) for a detailed listing of configuration options.

The project.clj file can be customized further with the use of profiles.

Documentation

Leiningen documentation is organized as a number of guides:

Plugins

Leiningen supports plugins which may contain both new tasks and hooks that modify behaivour of existing tasks. See the plugins wiki page for a full list. If a plugin is needed for successful test or build runs, (such as lein-tar) then it should be added to :plugins in project.clj, but if it's for your own convenience (such as swank-clojure) then it should be added to the :plugins list in the :user profile from ~/.lein/profiles.clj. See the profiles guide for details on how to add to your user profile. The plugin guide explains how to write plugins.

Contributing

Please report issues on the GitHub issue tracker or the mailing list. To join the mailing list, email leiningen@librelist.org; your first message to that address will subscribe you without being posted. Personal email addresses are not appropriate for bug reports. See the readme for the leiningen-core library and doc/PLUGINS.md for more details on how Leiningen's codebase is structured. Design discussions also occur in the #leiningen channel on Freenode.

Patches are preferred as GitHub pull requests, though patches from git format-patch are also welcome on the mailing list. Please use topic branches when sending pull requests rather than committing directly to master in order to minimize unnecessary merge commit clutter.

Contributors who have had a single patch accepted may request commit rights on the mailing list or in IRC. Please use your judgment regarding potentially-destabilizing work and branches. Other contributors will usually be glad to review topic branches before merging if you ask on IRC or the mailing list.

Contributors are also welcome to request a free Leiningen sticker by asking on the mailing list and mailing a self-addressed, stamped envelope.

Leiningen is mirrored at Gitorious and tested on Travis.

Building

You don't need to "build" Leiningen per se, but when you're using a checkout you will need to get its dependencies in place.

For the master branch, use Leiningen 1 to run lein install in the leiningen-core subproject directory. Alternately you can run mvn dependency:copy-dependencies in the same directory followed by cp -r target/dependency lib.

Once you've done that, symlink bin/lein to somewhere on your $PATH. Usually you'll want to rename your existing installation to keep them from interfering.

When the dependencies change you will also have to do rm .lein-classpath in the project root.

Using bin/lein alone from the master branch without a full checkout is not supported. If you want to just grab a shell script to work with, use the preview branch.

License

Thanks to Stuart Halloway for Lancet and Tim Dysinger for convincing me that good builds are important.

pingles/leiningen