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Leiningen plugin to make ClojureScript development easy.
Clojure JavaScript Shell

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README.md

lein-cljsbuild

This is a leiningen plugin that makes it easy (and quick) to compile ClojureScript source into JavaScript. It's similar to cljs-watch, but is driven via lein instead of via a standalone executable. This means that your project can depend on a specific version of lein-cljsbuild, fetch it via lein deps, and you don't have to install any special executables into your PATH.

Also, this plugin has built-in support for seamlessly sharing code between your Clojure server-side project and your ClojureScript client-side project.

Installation

You can install the plugin via lein:

$ lein plugin install lein-cljsbuild 0.0.7

Or by adding lein-cljs to your project.clj file in the :dev-dependencies section:

(defproject lein-cljsbuild-example "1.2.3"
  :dev-dependencies [[lein-cljsbuild "0.0.7"]])

Make sure you pull down the jar file:

$ lein deps

Just Give Me a Damned Example Already!

See the example-projects directory for a couple of simple examples of how to use lein-cljsbuild.

Also, see the sample.project.clj file in this directory for an exhaustive list of all options supported by lein-cljsbuild.

Configuration

The lein-cljsbuild configuration is specified under the :cljsbuild section of your project.clj file. A simple project might look like this:

(defproject lein-cljsbuild-example "1.2.3"
  :dev-dependencies [[lein-cljsbuild "0.0.7"]]
  :cljsbuild {
    ; The path to the top-level ClojureScript source directory:
    :source-path "src-cljs"
    ; The standard ClojureScript compiler options:
    ; (See the ClojureScript compiler documentation for details.)
    :compiler {
      :output-to "war/javascripts/main.js"  ; default: main.js in current directory
      :optimizations :whitespace
      :pretty-print true}})

If you'd like your ClojureScript to be compiled when you run lein compile, and deleted when you run lein clean, you can also add the following entry to your defproject config:

:hooks [leiningen.cljsbuild]

Usage

Once the plugin is installed, you can build the ClojureScript once:

$ lein cljsbuild once

Or you can have lein-cljsbuild watch your source files for changes and automatically rebuild them. This is recommended for development, as it avoids the time-consuming JVM startup for each build:

$ lein cljsbuild auto

To delete all of the JavaScript and ClojureScript files that lein-cljsbuild automatically generated during compilation, run:

$ lein cljsbuild clean

Sharing Code Between Clojure and ClojureScript

Sharing code with lein-cljsbuild is accomplished via the configuration of "crossovers". A crossover specifies a Clojure namespace, the content of which should be copied into your ClojureScript project. This can be any namespace that is available via the Java CLASSPATH, which includes your project's main :source-path by default.

When a crossover namespace is provided by your current project (either via the main :source-dir or one of the :extra-classpath-dirs in your project.clj file), the files that make up that namespace (recursively) will be monitored for changes, and will be copied to the ClojureScript project whenever modified.

Crossover namespaces provided by jar files cannot be searched recursively, and thus must be specified on a per-file basis. They are copied over once, when lein-cljsbuild begins compilation, and are not monitored for changes.

Of course, remember that since the namespace will be used by both Clojure and ClojureScript, it will need to only use the subset of features provided by both languages.

Assuming that your top-level directory structure looks something like this:

├── src-clj
│   └── example
│       ├── core.clj
│       ├── something.clj
│       └── crossover
│           ├── some_stuff.clj
│           └── some_other_stuff.clj
└── src-cljs
    └── example
        ├── core.cljs
        ├── whatever.cljs
        └── util.cljs

And your project.clj file looks like this:

(defproject lein-cljsbuild-example "1.2.3"
  :dev-dependencies [[lein-cljsbuild "0.0.7"]]
  :source-path "src-clj"
  :cljsbuild {
    :source-path "src-cljs"
    ; Each entry in the :crossovers vector describes a Clojure namespace
    ; that is meant to be used with the ClojureScript code as well.
    ; The files that make up this namespace will be automatically copied
    ; into the ClojureScript source path whenever they are modified.
    :crossovers [example.crossover]
    :compiler {
      :output-to "war/javascripts/main.js"  ; default: main.js in current directory
      :optimizations :whitespace
      :pretty-print true}})

Then lein-cljsbuild would copy files from src-clj/example/crossover to src-cljs/example/crossover, and you'd end up with this:

├── src-clj
│   └── example
│       ├── a_file.clj
│       ├── core.clj
│       └── crossover
│           ├── some_stuff.clj
│           └── some_other_stuff.clj
└── src-cljs
    └── example
        ├── a_different_file.cljs
        ├── crossover
        │   ├── some_stuff.cljs
        │   └── some_other_stuff.cljs
        ├── whatever.cljs
        └── util.cljs

With this setup, you would probably want to add src-cljs/example/crossover to your .gitignore file (or equivalent), as its contents are updated automatically by lein-cljsbuild.

Sharing Macros Between Clojure and ClojureScript

In ClojureScript, macros are still written in Clojure, and can not be written in the same file as actual ClojureScript code. Also, to use them in a ClojureScript namespace, they must be required via :require-macros rather than the usual :require.

This makes using the crossover feature to share macros between Clojure and ClojureScript a bit difficult, but lein-cljsbuild has some special constructs to make it possible.

Three things need to be done to use lein-cljsbuild to share macros.

1. Keep Macros in Separate Files

These examples assume that your project uses the src-clj/example/crossover directory, and that all of the macros are in a file called src-clj/example/crossover/macros.clj.

2. Tell lein-cljsbuild Which Files Contain Macros

Add this magical comment to any crossover files that contain macros:

;*CLJSBUILD-MACRO-FILE*;

This tells lein-cljsbuild to refrain from copying the .clj files into the ClojureScript directory. This step can be skipped if the macro file is not included in any of the crossover namespaces.

3. Use Black Magic to Require Macros Specially

In any crossover Clojure file, lein-cljsbuild will automatically erase the following string (if it appears):

;*CLJSBUILD-REMOVE*;

This magic can be used to generate a ns statement that will work in both Clojure and ClojureScript:

(ns example.crossover.some_stuff
  (:require;*CLJSBUILD-REMOVE*;-macros
    [example.crossover.macros :as macros]))

Thus, after removing comments, Clojure will see:

(ns example.crossover.some_stuff
  (:require
    [example.crossover.macros :as macros]))

However, lein-cljsbuild will remove the ;*CLJSBUILD-REMOVE*; string entirely, before copying the file. Thus, ClojureScript will see:

(ns example.crossover.some_stuff
  (:require-macros
    [example.crossover.macros :as macros]))

And thus the macros can be shared.

License

Source Copyright © Evan Mezeske, 2011-2012. Released under the Eclipse Public License - v 1.0. See the file COPYING.

Contributors

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