Leiningen

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“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 offers a recent version of Leiningen, try that first as long as it has version 2.x.

Leiningen installs itself on the first run of the lein shell script; there is no separate install script. Follow these instructions to install Leiningen manually:

Make sure you have Java installed; OpenJDK version 8 is recommended at this time.
Download the lein script from the stable branch of this project.
Place it on your $PATH. (~/bin is a good choice if it is on your path.)
Set it to be executable. (chmod +x ~/bin/lein)
Run it.

Windows users can use the above script in the Linux subsystem or try the batch file or Powershell version instead.

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

$ lein deploy clojars # publish the project to Clojars as a library

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."
  :license "Eclipse Public License 1.0"
  :url "http://github.com/technomancy/myproject"
  :dependencies [[org.clojure/clojure "1.8.0"]]
  :plugins [[lein-tar "3.2.0"]])

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:

Usage

Development

Plugins

Leiningen supports plugins which may introduce new 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 lein-pprint) then it should be added to the :plugins list in the :user profile in ~/.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.

License

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