Introduction

Composer is build with extensibility at its core. Everything within the application is built using the same App Framework APIs, from the UI down to data and business logic, anything in Composer can be customized and enhanced.

Anatomy of a Plugin

A Plugin consists of one or more plugin modules, which are activated by activation events and contribute capabilities.

PluginModule

A PluginModule is a unit of containment of modular functionality that can be provided to an application. Activation of a module is async allowing for code to split and loaded lazily. The activate function of module takes the plugins context as its only argument. In addition to the event which activates the module, events can be fired before and after the activation of a module. This allows modules to ensure certain dependencies are activated prior to their own activation based on the graph of activation events.

ActivationEvent

An ActivationEvent is a unique string identifier representing an event. This is expected to be a URI, where initial parts are often the id of the plugin whose package defines the event. The framework defines some common activation events, however plugins are free to define their own as well.

Capability

A Capability is a unique string identifier with a Typescript type associated with it. When a capability is contributed to the application an implementation of the interface is provided. Many of the same capability can be contributed to the application and when they are requested all will be returned. The framework defines some common capabilities, however plugins are free to define their own as well.

PluginsContext

The PluginsContext facilitates the dependency injection between plugin modules by allowing them contribute and request capabilities from each other. It tracks the capabilities that are contributed in an in-memory live object. This allows the application to subscribe to this state and incorporate plugins which are added dynamically.