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in

Generic plugin loader facility.

in - Getting Started - Documentation - constructor options - context - mountDirectory(directory,options,context) - find(directory) - sort(plugins) - sortFilter - sortByDependencies - normalize(plugins) - String - Array - Object - Mixed - filter(plugins) - load(plugins, options={}) - mount - mountHandler - afterMount(context) - Examples - Release History - License

Getting Started

Install the module with: npm install in

const PluginLoader = require('in');

A plugin should expose a init function.

module.exports.init = function(app, config){};

A module can expose a priority value:

module.exports.priority = 5000;

A negative value indicates a higher priority

A module can expose a 'dependencies' value:

module.exports.dependencies = ['logger'];

Documentation

A plugin is nothing more than a regular Node module. By default, we expect plugins to expose an init function that takes two arguments:

context
config

constructor options

context

This is where all plugins will be mounted. This would normally be your application instance.

mountDirectory(directory,options,context)

It will mount all plugins found in directory into the provided context.

This is in effect applying find, filter, load, sort, and mount in that order.

find(directory)

Scans a directory for files and directories, returning a list of absolute paths to the files. It target is not an absolute path, we resolve it against basepath.

sort(plugins)

Sorts an array of plugins after they have been loaded. By default it uses sortFilter:

sortFilter

It will looks for module.exports.priority and sort based on that:

function _sortFilter(plugins){
	function filter(a, b) {
		function p(i){
			return i.priority === undefined ? 0 : i.priority;
		}
		return p(a) < p(b) ? -1 : 1;
	}
	return plugins.sort(filter);
}

sortByDependencies

The library also exposes a sortByDependencies filter, which you can use instead of the default sortFilter.

const loader = new PluginLoader({
    sortFilter: require('in').sortByDependencies
});

Modules should expose a dependencies array listing the ids of depended modules.

module.exports.dependencies = ['logger', 'persistence'];

normalize(plugins)

When we call load we apply the normalize function which will ensures that plugins can be any of the following:

String

const plugins = '/Users/application/plugins/authentication';

Output after calling normalize:

[
    {
        "id": "authentication",
        "path": "/Users/application/plugins/authentication",
        "config": {}
    }
]

Array

const plugins = ['/Users/application/plugins/authentication'];

Output after calling normalize:

[
    {
        "id": "authentication",
        "path": "/Users/application/plugins/authentication",
        "config": {}
    }
]

Object

const plugins = {
    '/Users/application/plugins/authentication': { hash: 'sh1' }
};

Output after calling normalize:

[
    {
        "id": "authentication",
        "path": "/Users/application/plugins/authentication",
        "config": {
            "hash": "sh1"
        }
    }
]

Mixed

const plugins = [
    {'/Users/application/plugins/authentication':{ hash: 'sh1' }},
    'debug'
];

Output after calling normalize:

[
    {
        "id": "authentication",
        "path": "/Users/application/plugins/authentication",
        "config": {
            "hash": "sh1"
        }
    },
    {
        "id": "debug",
        "path": "debug",
        "config": {}
    }
]

filter(plugins)

Public: Apply minimatch patterns against paths, an array of paths. The default pattern is ['**', '!node_modules', '!.git'] Returns a Promise which once resolved will contain an Array of filtered paths.

load(plugins, options={})

Given a list of plugins, create a plugin object with metadata and the result of requireing the module.

We create a bean per plugin:

{
    id: 'logger',
    path: '/Users/in/examples/plugins/logger.js',
    config: {},
    plugin: { init: [Function], priority: -100 },
    isLocal: true
}

mount

Makes plugins available to the provided context by calling mountHandler to previously loaded plugins.

mountHandler

Adds a plugin to the provided context.

function _mount(bean, context, config={}){
	config = extend({}, bean.config, config);
	var plugin = bean.plugin;
	if(typeof bean.config === 'function') return bean.config(plugin, context, config);
	if(typeof bean.config.mount === 'function') return bean.config.mount(plugin, context, config);
	if(typeof plugin.init === 'function') return plugin.init(context, config);
	return context[bean.id] = plugin;
}

afterMount(context)

Function that will be called right after mount

Examples

Look at the examples directory. Run it with node examples/index.js.

Directory structure:

index.js
plugins
- repl.js
- pubsub.js
- logger.js
- authentication
  - index.js

const PluginManager = require('..');
const EventEmitter = require('events');

const app = new EventEmitter();

app.on('plugins.ready', _ => {
    app.logger.info('Application plugins loaded');
});

const manager = new PluginManager({
    context: app,
    basepath: __dirname,
	afterMount: (context) => context.emit('plugins.ready')
});

manager.mountDirectory('./plugins')
    .catch(console.error);

logger.js:

module.exports.init = function(app, config) {
    app.logger = console;
    app.logger.info('Plugin logger loaded!');
};

module.exports.priority = -100;

repl.js:

module.exports.init = function(app, config) {

    app.repl = {
        context: {app}
    };

    app.logger.info('Plugin REPL loaded!');
};

pubsub.js:

module.exports.init = function(app, config) {
    app.pubsub = {
        publibsh: function(type, event){
            app.logger.warn('publish: %s. payload: %s', type, event);
        },
        subscribe: function(type, handler){
            app.logger.warn('subscribe to %s', type);
        }
    };
    app.logger.info('Plugin pubsub loaded!');
};

authentication/index.js:

module.exports.init = function(app, config) {
    app.auth = {
        check: function(){}
    };
    app.logger.info('Plugin auth loaded!');
};

module.exports.priority = 500;

node examples/load/index.js:

Plugin logger loaded!
Plugin REPL loaded!
Plugin pubsub loaded!
Plugin auth loaded!
Application plugins loaded

Release History

2020-06-04: v0.18.2 hotfix release
2020-06-04: v0.18.0 Add support for sub directories in plugins target dir
2019-09-08: v0.17.0 Update version of dependencies
- Export normalizePath from lib/normalizeArguments.js
- Export getIdFromPath from lib/normalizeArguments.js
2019-08-26: v0.16.2 Update version of dependencies
2019-07-13: v0.16.0 Remove synchronous file access
2019-07-13: v0.15.0 Update version of dependencies
2016-11-24: v0.9.0 Added sortByDependencies
2016-11-18: v0.8.0 Update mount to take in afterMount in options
2016-11-14: v0.7.0 normalizePath use basepath from argument
2016-11-13: v0.6.0 Refactoring mount
2016-10-24: v0.5.0 Added afterMount
2016-10-23: v0.4.0 Big update
- Added examples
- Added documentation
- Added mountDirectory