204 lines
8.6 KiB
Markdown
204 lines
8.6 KiB
Markdown
# Leiningen
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> "Leiningen!" he shouted. "You're insane! They're not creatures you can
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> fight--they're an elemental--an 'act of God!' Ten miles long, two
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> miles wide--ants, nothing but ants! And every single one of them a
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> fiend from hell..."
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> -- from Leiningen Versus the Ants by Carl Stephenson
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Leiningen is a build tool for Clojure designed to not set your hair on fire.
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Building Clojure projects with tools designed for Java can be an
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exercise in frustration. If you use Ant, you end up copying around a
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lot of the same tasks around between XML files on all your projects;
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there's a lot of repetition. Maven avoids repetition, but provides
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very little transparency into what's really going on behind the scenes
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and forces you to become a Maven expert to script a nontrivial
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build. Either way you end up writing far more XML than is necessary.
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With Leiningen, your build is described using Clojure. You can put any
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code you like in your project.clj file; the only requirement is that
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it includes a call to defproject. You can define your own tasks in
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there if you need to, but the majority of projects should be able to
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get by on the tasks that are provided with Leiningen. If you do find a
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common task that you need to add, you can implement it as a plugin
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rather than copying and pasting among each of your projects.
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## Installation
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1. Download the script: http://github.com/technomancy/leiningen/raw/stable/bin/lein
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2. Place it on your path and chmod it to be executable.
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3. Run: <tt>lein self-install</tt>
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This only works with stable versions of Leiningen; for development
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versions see "Hacking" below.
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## Usage
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$ lein deps # install dependencies in lib/
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$ lein test [TESTS] # run the tests in the TESTS namespaces, or all tests
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$ lein compile # ahead-of-time compile into classes/
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$ lein repl # launch a REPL with the project classpath configured
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$ lein clean # remove all build artifacts
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$ lein jar # create a jar of the project
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$ lein uberjar # create a standalone jar that contains all dependencies
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$ lein pom # output a pom.xml file for interop with Maven
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$ lein install # install in local repository
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$ lein help [TASK] # show a list of tasks or help for a given TASK
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$ lein new NAME # generate a new project skeleton
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## Configuration
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Place a project.clj file in the project root that looks something like this:
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(defproject leiningen "0.5.0-SNAPSHOT"
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:description "A build tool designed not to set your hair on fire."
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:url "http://github.com/technomancy/leiningen"
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:dependencies [[org.clojure/clojure "1.1.0-alpha-SNAPSHOT"]
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[org.clojure/clojure-contrib "1.0-SNAPSHOT"]
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[ant/ant-launcher "1.6.2"]
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[org.apache.maven/maven-ant-tasks "2.0.10"]]
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:dev-dependencies [[org.clojure/swank-clojure "1.0"]])
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Other keys accepted:
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* :namespaces - if set, only AOT-compile namespaces listed here rather
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than all namespaces found in src/ directory.
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* :main - specify a namespace to use as main for an executable jar.
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* :repositories - additional maven repositories to search for dependencies.
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* :source-path, :compile-path, :library-path, :test-path, :resources-path -
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alternate paths for src/, classes/, lib/, resources/, and test/ directories.
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## FAQ
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**Q:** How do you pronounce Leiningen?
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**A:** It's LINE-ing-en. I think.
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**Q:** What does this offer over [Lancet](http://github.com/stuarthalloway/lancet)?
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**A:** Lancet is more of a library than a build tool. It doesn't predefine
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any tasks apart from what Ant itself offers, so there is nothing
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Clojure-specific in it. Leiningen builds on Lancet, but takes
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things further. In addition, it includes some Maven functionality
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for dependencies.
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**Q:** But Maven is terrifying!
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**A:** That's not a question. Anyway, Leiningen only uses the dependency
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resolution parts of Maven, which are quite tame. For the actual
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task execution cycles it uses Ant under the covers via Lancet.
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**Q:** But Ant is terrifying!
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**A:** That's [true](http://www.defmacro.org/ramblings/lisp.html). Ant is
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an interpreter for a [procedural language with a regrettable
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syntax](http://blogs.tedneward.com/2005/08/22/When+Do+You+Use+XML+Again.aspx).
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But if you treat it as a standard library of build-related
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functions and are able to write it with a more pleasing syntax, it's
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not bad.
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**Q:** What if my project depends on jars that aren't in any repository?
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**A:** Open-source jars can be uploaded to Clojars (see "Publishing"
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below), though be sure to use the groupId of "org.clojars.$USERNAME"
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in order to avoid conflicts and to allow the original authors to
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claim it in the future once they get around to uploading.
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Alternatively you can install into your local repository in ~/.m2
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with Maven for Java libs or "lein install" for Clojure libs.
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**Q:** Is it possible to exclude indirect dependencies?
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**A:** Yes. Some libraries, such as log4j, depend on projects that are
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not included in public repositories and unnecessary for basic
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functionality. Projects listed as :dependencies may exclude
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any of their dependencies by using the :exclusions key, as demonstrated here:
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[log4j "1.2.15" :exclusions [javax.mail/mail
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javax.jms/jms
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com.sun.jdmk/jmxtools
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com.sun.jmx/jmxri]]
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**Q:** How should I pick my version numbers?
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**A:** Use [semantic versioning](http://semver.org).
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**Q:** What happened to [Corkscrew](http://github.com/technomancy/corkscrew)?
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**A:** I tried, but I really couldn't make the wine metaphor work. That,
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and the Plexus Classworlds container was an ornery beast causing
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much frustration. The maven-ant-tasks API is much more manageable.
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**Q:** What about Windows?
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**A:** Patches welcome.
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## Publishing
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If your project is a library and you would like others to be able to
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use it as a dependency in their projects, you will need to get it into
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a public repository. While it's possible to maintain your own or get
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it into Maven central, the easiest way is to publish it at
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[Clojars](http://clojars.org), which is a Clojure-specific repository
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for open-source code. Once you have created an account there,
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publishing is easy:
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$ lein pom
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$ scp pom.xml $PROJECT.jar clojars@clojars.org:
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Once that succeeds it will be available for other projects to depend
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on. Leiningen adds Clojars and [the Clojure nightly build
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snapshots](http://build.clojure.org) to the default repositories.
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## Known Issues
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* The repl task will use the version of Clojure and Contrib that
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Leiningen uses, not the one specified by your project.
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* Projects that use Clojure 1.0 are supported, but the test task does
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not support clojure.contrib.test-is. This may be added with a plugin
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later.
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* Due to a bug in contrib's build, the swank plugin may not work with
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projects that use Clojure 1.0 and contrib together.
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## Hacking
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You'll need to bootstrap using a stable release before you can hack on
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Leiningen. Grab the stable bin script (linked under "Installation"
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above), put it on your $PATH as "lein-stable", and do "lein-stable
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self-install". Then run "lein-stable deps" in your checkout. When that
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finishes, symlink bin/lein from your checkout to your path. This will
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make "lein" run from your checkout while "lein-stable" uses the jar
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self-installed in ~/.m2.
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The [mailing list](http://groups.google.com/group/clojure) and the
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leiningen or clojure channels on Freenode are the best places to
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bring up questions or suggestions. If you're planning on adding a
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feature or fixing a nontrivial bug, please discuss it first to avoid
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duplicating effort. If you haven't discussed it on the mailing list,
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please include in your pull request details of what problem your patch
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intendeds to solve as well as the approach you took.
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Contributions are preferred as either Github pull requests or using
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"git format-patch" and the mailing list as is requested [for
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contributing to Clojure itself](http://clojure.org/patches). Please
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use standard indentation with no tabs, trailing whitespace, or lines
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longer than 80 columns. If you've got some time on your hands, reading
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this [style guide](http://mumble.net/~campbell/scheme/style.txt)
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wouldn't hurt either.
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Leiningen is extensible; you can define new tasks in plugins. Add your
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plugin as a dev-dependency of your project, and you'll be able to call
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"lein $YOUR_COMMAND". See the lein-swank directory for an example of a
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plugin.
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## License
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Copyright (C) 2009 Phil Hagelberg, Alex Osborne, and Dan Larkin
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Thanks to Stuart Halloway for Lancet and Tim Dysinger for convincing
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me that good builds are important.
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Distributed under the Eclipse Public License, the same as Clojure
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uses. See the file COPYING.
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