scriptcraft/docs/release-notes.md

2013 12 24

'Modules' release

Modules in ScriptCraft

ScriptCraft now has a simple module loading system. ScriptCraft now uses the CommonJS module contract - that is - the same module system used by Node.js. All of the javascript code which comes bundled with ScriptCraft has been modified so that it conforms to the CommonJS module system.

What this means for plugins you've developed using ScriptCraft

If you have written plugins using a previous version of ScriptCraft then you have 2 options...

1. Continue using the previous version of ScriptCraft.
2. Update your plugins to work with the ScriptCraft 'Modules' release.

... Option 2 should be relatively straightforward if you follow these steps...

1. Copy your own custom plugins from the js-plugins directory to the new scriptcraft/plugins directory.
2. In your javascript code any functions, objects or variables which you want to expose for use by others should be exposed using the special exports variable. All other code within your .js files will now be private by default. See below for details on how CommonJS/Node.js modules work.

If you have any questions or concerns or need help converting your existing javascript plugin, contact please post questions on the ScriptCraft forum or open an issue on the Github project

In ScriptCraft, files and modules are in one-to-one correspondence. As an example, foo.js loads the module circle.js in the same directory. ScriptCraft now uses the same module system as Node.js - see Node.js Modules for more details.

The contents of foo.js:

var circle = require('./circle.js');
echo( 'The area of a circle of radius 4 is '
           + circle.area(4));

The contents of circle.js:

var PI = Math.PI;

exports.area = function (r) {
  return PI * r * r;
};

exports.circumference = function (r) {
  return 2 * PI * r;
};

The module circle.js has exported the functions area() and circumference(). To add functions and objects to the root of your module, you can add them to the special exports object.

Variables local to the module will be private, as though the module was wrapped in a function. In this example the variable PI is private to circle.js.

If you want the root of your module's export to be a function (such as a constructor) or if you want to export a complete object in one assignment instead of building it one property at a time, assign it to module.exports instead of exports.

Module Loading

When the ScriptCraft Java plugin is first installed, a new subdirectory is created in the craftbukkit directory. If your craftbukkit directory is called 'craftbukkit' then the new subdirectories will be ...

• craftbukkit/scriptcraft/
• craftbukkit/scriptcraft/plugins
• craftbukkit/scriptcraft/modules
• craftbukkit/scriptcraft/lib

... The plugins, modules and lib directories each serve a different purpose.

The plugins directory

At server startup the ScriptCraft Java plugin is loaded and begins automatically loading and executing all of the modules (javascript files with the extension .js) it finds in the scriptcraft/plugins directory. All modules in the plugins directory are automatically loaded into the global namespace. What this means is that anything a module in the plugins directory exports becomes a global variable. For example, if you have a module greeting.js in the plugins directory....

exports.greet = function() {
    echo('Hello ' + self.name);
};

... then greet becomes a global function and can be used at the in-game (or server) command prompt like so...

/js greet()

... This differs from how modules (in NodeJS and commonJS environments) normally work. If you want your module to be exported globally, put it in the plugins directory. If you don't want your module to be exported globally but only want it to be used by other modules, then put it in the modules directory instead. If you've used previous versions of ScriptCraft and have put your custom javascript modules in the js-plugins directory, then put them in the scriptcraft/plugins directory. To summarise, modules in this directory are ...

• Automatically loaded and run at server startup.
• Anything exported by modules becomes a global variable.

The modules directory

The module directory is where you should place your modules if you don't want to export globally. In javascript, it's considered best practice not to have too many global variables, so if you want to develop modules for others to use, or want to develop more complex mods then your modules should be placed in the modules directory. Modules in the modules directory are not automatically loaded at startup, instead, they are loaded and used by other modules/plugins using the standard require() function. This is the key difference between modules in the plugins directory and modules in the modules directory. Modules in the plugins directory are automatically loaded and exported in to the global namespace at server startup, modules in the modules directory are not.

The lib directory

Modules in the lib directory are for use by ScriptCraft and some core functions for use by module and plugin developers are also provided. The lib directory is for internal use by ScriptCraft. Modules in this directory are not automatically loaded nor are they globally exported.