dynamic-plugin-framework

Dynamic plugin framework for Deno based on Javascript Modules and import() function.

Overview

This project provides a framework for defining plugins which can be dynamically discovered and imported into a running process.

Key Features

Universal support for both Deno and browser runtimes
Dynamic plugin import using Javascript dynamic import
ES2015 module based
Written in Typescript

Key Concepts

The framework’s key concepts are borrowed from the Eclipse Project’s extension framework. The key concepts are:

A Plugin provides one or more Extension implementations.
Each Extension implementation declares an ExtensionPoint identifier and an ExtensionFactory via an ExtensionDescriptor.
A HostApplication instantiates a PluginManager.
The HostApplication can register one or more ExtensionPoint identifiers that the PluginManager should be aware of.
The PluginManager scans one or more PluginRepository implementations to find and register Plugin objects for any ExtensionPoint identifiers it is aware of.
The HostApplication uses the PluginManager to query for and select an Extension for a desired ExtensionPoint identifier.
The PluginManager uses the associated ExtensionFactory to instantiate the selected Extension.

The following high level class diagram illustrates these relationships:

classDiagram
    direction LR

    class HostApplication {
    }

    class ExtensionPoint1 {
        <<interface>>
        EXTENSION_POINT_1
    }

    class Plugin {
        <<interface>>
    }

    class PluginManager {
        <<interface>>
    }

    class PluginRepository {
        <<interface>>
    }

    class ExtensionDescriptor {
        <<interface>>
    }

    class ExtensionFactory {
        <<interface>>
    }

    class Plugin1 {
    }

    class Extension1Descriptor {
    }

    class Extension1Factory {
    }

    class Extension1 {
    }

    PluginRepository --> "0..*" Plugin
    PluginManager -->  "1..*" PluginRepository: scans
    Plugin --> "1..*" ExtensionDescriptor
    ExtensionDescriptor --> ExtensionFactory
    PluginManager --> "0..*" Plugin : registers
    PluginManager ..> ExtensionFactory : invokes
    Extension1Factory ..|> ExtensionFactory
    Extension1Descriptor ..|> ExtensionDescriptor
    Plugin1 ..|> Plugin
    Extension1 ..|> ExtensionPoint1
    Plugin1 --> Extension1Descriptor
    Extension1Descriptor --> Extension1Factory
    Extension1Factory ..> Extension1 : creates
    Extension1Descriptor ..> ExtensionPoint1: declares
    HostApplication --> PluginManager
    HostApplication ..> ExtensionPoint1: defines

The following sequence diagram illustrates the key steps for a HostApplication to use a PluginManager for discovery and registration of Plugin instances:

%%{init: { "sequence": { "mirrorActors":false }}}%%
sequenceDiagram
    HostApplication->>PluginManager:<<static import>>
    Note over PluginRepository1,PluginRepository2: May use an index or scan plugins directly
    HostApplication->>PluginManager:registerExtensions(EXTENSION_POINT_1)
    activate PluginManager
    PluginManager->>PluginRepository1:scanForExtensions(EXTENSION_POINT_1)
    activate PluginRepository1
    PluginRepository1-->>PluginManager:ExtensionEntry[]
    deactivate PluginRepository1
    PluginManager->>PluginRepository2:scanForExtensions(EXTENSION_POINT_1)
    activate PluginRepository2
    PluginRepository2-->>PluginManager:ExtensionEntry[]
    deactivate PluginRepository2
    PluginManager-->>HostApplication:ExtensionInfo[]
    deactivate PluginManager

Once registration has been performed, the HostApplication may query the PluginManager for Extensions of known ExtensionPoints and then instantiate them:

%%{init: { "sequence": { "mirrorActors":false, diagramMarginY: 0 }}}%%
sequenceDiagram
    HostApplication->>PluginManager:getRegisteredExtensions(EXTENSION_POINT_1)
    activate PluginManager
    PluginManager->>PluginManager:filterExtensions
    PluginManager->>HostApplication:ExtensionInfo[]
    deactivate PluginManager
    HostApplication->>HostApplication:select Extension1
    HostApplication->>PluginManager:instantiate(extension1Handle)
    activate PluginManager
    PluginManager->>PluginRepository1:getExtensionDescriptorFromExtensionEntry(extensionEntry)
    PluginRepository1->>Plugin1:<<dynamic import>>
    Plugin1-->>PluginManager:ExtensionDescriptor
    PluginManager->>Extension1Factory:create()
    activate Extension1Factory
    Extension1Factory->>Extension1:<<new>>
    Extension1Factory-->>PluginManager:Extension1
    deactivate Extension1Factory
    PluginManager-->>HostApplication:Extension1
    deactivate PluginManager
    HostApplication->>Extension1:extensionPoint1Method
    activate Extension1
    deactivate Extension1

As ExtensionPoints are simply Typescript objects, for the purposes of testing or validation, it is possible to bypass the framework altogether and import an Extension and use it directly:

%%{init: { "sequence": { "mirrorActors":false }}}%%
sequenceDiagram
    HostApplication->>Extension1:<<static import>>
    HostApplication->>Extension1:extensionPoint1Method
    activate Extension1
    deactivate Extension1

Examples

The following example projects are available which support execution in both a terminal and a browser:

API

The following diagram provides an overview of the Plugin API:

classDiagram
    class Plugin {
        <<interface>>
        pluginData: any
    }

    class ExtensionDescriptor {
        <<interface>>
        extensionPoint
        extensionData: any
    }

    class ExtensionFactory {
        <<interface>>
        create(hostData: any) Extension
    }

    Plugin --> "1..*" ExtensionDescriptor: extensionDescriptors
    ExtensionDescriptor --> ExtensionFactory: factory

The following diagram provides an overview of the PluginManager API:

classDiagram
    class PluginManager {
        <<interface>>
        registerExtensions(extensionPoint)
        getRegisteredExtensions(extensionPoint) Set<ExtensionInfo>
        instantiate(extensionHandle, hostData: Map<string, string>) Extension
    }

    class ExtensionInfo {
        <<interface>>
        extensionHandle
        extensionData: Map<string, string>
        pluginData: Map<string, string>
    }

API docs for the library:

API Documentation

Development

Test: deno test -A --unstable

Lint: deno fmt

The following diagram provides an overview of the main internal classes:

classDiagram
    class PluginManager {
        <<interface>>
    }

    class DefaultPluginManager {
    }

    class ExtensionPointRegistry {
        <<interface>>
    }

    class ExtensionRegistry {
        <<interface>>
    }

    class PluginRepository {
        <<interface>>
    }

    class UrlListPluginRepository {
    }

    class InMemoryExtensionRegistry {
    }

    class InMemoryExtensionPointRegistry {
    }

    PluginManager <|.. DefaultPluginManager
    ExtensionPointRegistry <|.. InMemoryExtensionPointRegistry
    ExtensionRegistry <|.. InMemoryExtensionRegistry
    DefaultPluginManager --> ExtensionPointRegistry
    DefaultPluginManager --> ExtensionRegistry
    DefaultPluginManager --> "1..*" PluginRepository
    PluginRepository <|.. UrlListPluginRepository