lein-oneoff

Dealing with dependencies and the classpath can be a pain. Leiningen takes most of the pain away, but creating a new leiningen project for a simple one-off script may sometimes feel like overkill. This is where lein-oneoff comes in.

With the help of lein-oneoff you can open a file, declare dependencies at the top, and write the rest of the code as usually. lein-oneoff will let you run the file or open a repl session while taking care of fetching dependencies and constructing the classpath automatically.

You might find lein-oneoff useful when you want to play with a brand new alpha release of clojure, but would rather not dowload the jar manually, when you think you know the answer to a question about a particular library posted to the clojure mailing list, but would rather test your idea out in the repl before posting the answer, or when you quickly want to analyse and plot some data using Incanter.

Usage

lein-oneoff scripts usually consist of a single file. Dependencies should be stated at the top using the defdeps form. You may optionally prefix the defdeps form with the #_ reader macro (ignore next form). Here's an example:

#_(defdeps
    [[org.clojure/clojure "1.2.0"]
     [compojure "0.5.2"]
     [ring/ring-jetty-adapter "0.3.3"]])

(ns example
  (:use [compojure.core :only [defroutes GET]]
        [ring.adapter.jetty :only [run-jetty]]))

(defroutes routes
  (GET "/" [] "Hello world!"))

(def server
  (run-jetty routes {:port 8080 :join? false}))

Save this file as example.clj, then run it with:

$ lein oneoff example.clj

This command will resolve the specified dependencies and install them into the local maven repository (~/.m2/repository) unless already installed, and then run example.clj with the classpath properly set.

The defdeps form

The defdeps form must be the first form in the file. It has the following signature:

(defdeps dependencies additional-entries?)

where dependencies should be specified as a vector using the same syntax as inside regular leiningen defproject form under the :dependencies key. The second argument is an optional map of additional standard defproject entries. Please note that not all of the available leinigen options make sense for a one-off script and might not work correctly. Adding a #_ prefix will make it possible to ignore the defdeps form when re-compiling the file in a repl.

One of the entries that can be useful is the :repositories entry. Here's an example:

(defdeps
  [[org.clojure/clojure "1.3.0-alpha3"]
   [org.apache.pivot/pivot-web "1.5.2"]]
  {:repositories
   {"apache" "https://repository.apache.org/content/repositories/releases/"}})

The defdeps form may be omitted in which case the only assumed dependency is org.clojure/clojure of the same version as your leiningen installation is using.

exec

To execute (load) a one-off script, use the --exec (or -e for short) command. Any arguments positioned after the script name are passed to the script as *command-line-args*.

$ lein oneoff --exec example.clj arg1 arg2
$ lein oneoff -e example.clj

The --exec command is the default, so you can omit it altogether.

$ lein oneoff example.clj
$ lein oneoff example.clj 8080 127.0.0.1

repl

To start a repl in the context of a one-off script, use the --repl command (or its shorter equivalent, -r):

$ lein oneoff --repl example.clj
$ lein oneoff -r example.clj

classpath

lein-oneoff offers an equivalent to leiningen's built-in classpath task which prints the project's classpath for one-off scripts:

$ lein oneoff --classpath example.clj
$ lein oneoff -cp example.clj

Installation

This plugin should be installed as a global user-level leiningen plugin. You can install it by adding the following line to ~/.lein/profiles.clj:

{:user {:plugins [[lein-oneoff "0.3.2"]]}}

This version of lein-oneoff works with leiningen 2.0.0 or newer. If you are using Leinigen 1.x, please check out release 0.2.0.

License

Copyright (C) 2010 Matjaz Gregoric

Distributed under the Eclipse Public License, the same as Clojure.