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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 a build tool for Clojure designed to not set your hair on fire.

Installation

Put bin/lein on your $PATH and run: $ lein self-install

Usage

$ lein deps # install dependencies in lib/

$ lein test [PRED] # run the project's tests, optionally filtered on PRED

$ lein compile # ahead-of-time compile into classes/

$ lein repl # launch a REPL with the project classpath configured

$ lein clean # remove all build artifacts

$ lein jar # create a jar of the project

$ lein uberjar # create a standalone jar that contains all dependencies

$ lein swank [PORT] # launch swank server for Emacs to connect

TODO: install, new, help, deploy, pom

Configuration

Place a project.clj file in the project root that looks something like this:

(defproject leiningen "1.0-SNAPSHOT"
  :dependencies [[org.clojure clojure "1.1.0-alpha-SNAPSHOT"]
                 [org.clojure clojure-contrib "1.0-SNAPSHOT"]
                 [org.clojure lancet "1.0-SNAPSHOT"]
                 [org.apache.ant ant "1.7.1"]
                 [org.apache.ant ant-launcher "1.7.1"]
                 [org.apache.maven maven-ant-tasks "2.0.10"]])

Other keys you can set are :namespaces to compile if you don't want all of them AOT'd as well as a :main namespace for building executable jars.

FAQ

Q: How do you pronounce Leiningen?
A: It's LINE-ing-en. I think.

Q: What does this offer over Lancet?
A: Lancet is more of a library than a build tool. It doesn't predefine any tasks apart from what Ant itself offers, so there is nothing Clojure-specific in it. Leiningen builds on Lancet, but takes things further. In addition, it includes some Maven functionality for dependencies.

Q: But Maven is terrifying!
A: That's not a question. Anyway, Leiningen only uses the dependency resolution parts of Maven, which are quite tame. For the actual task execution cycles it uses Ant under the covers via Lancet.

Q: But Ant is terrifying!
A: That's true. Ant is an interpreter for a procedural language with a regrettable syntax. But if you're able to write it with a more pleasing syntax, it's not so bad.

Q: What happened to Corkscrew?
A: I tried, but I really couldn't make the wine metaphor work. That, and the Plexus Classworlds container was an ornery beast causing much frustration.

Q: What about Windows?
A: Patches welcome.

Hacking

Working on the Leiningen codebase has a few unique challenges since there's a bit of a chicken-and-egg bootstrap problem. To go from a clean checkout to a working environment, the following steps are necessary:

  1. Place bin/lein on your $PATH somewhere.
  2. Do a self-install of leiningen (from outside the checkout tree).
  3. Place ~/.leiningen.jar in lib.
  4. Invoke "lein compile" followed by "lein deps".
  5. Remove .leiningen.jar from lib.
  6. Invoke "lein uberjar", and place the jar in ~/.leiningen.jar for future use.

License

Copyright (C) 2009 Phil Hagelberg

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

Distributed under the Eclipse Public License, the same as Clojure uses. See the file COPYING.