Extension System Design

This document describes the Morphir extension system, including current implementation and future vision.

Overview

The Morphir extension system allows adding support for new languages and targets through WASM-based extensions. Extensions implement the Frontend and/or Backend traits to provide language-specific functionality.

Current Implementation

Architecture

The current implementation uses:

  • Extism: WASM runtime for loading and executing extensions
  • Extension Registry: Manages loaded extensions
  • Extension Container: Wraps Extism plugin with Morphir-specific functionality

Extension Types

Extensions can implement:

  • Frontend: Converts source code → Morphir IR V4
  • Backend: Converts Morphir IR V4 → Generated code
  • Transform: IR-to-IR transformations
  • Validator: IR validation

Extension Discovery

Extensions are discovered in this order:

  1. Builtin Extensions: Bundled with CLI (e.g., Gleam)
  2. Config Extensions: Specified in morphir.toml
  3. Registry Extensions: Installed from extension registry

Extension Loading 

// Discover extension
let extension = registry.find_extension_by_language("gleam").await?;

// Call extension method
let result: serde_json::Value = extension
    .call("morphir.frontend.compile", params)
    .await?;

Future Vision: Actor Model

The design documents describe a sophisticated actor-based architecture:

Extension Manager

Central coordinator as a singleton Kameo actor:

  • Manages extension lifecycle
  • Routes extension requests
  • Coordinates extension hosts

Extension Hosts

One actor per protocol type:

  • JSON-RPC Host: JSON-RPC protocol extensions
  • gRPC Host: gRPC protocol extensions
  • Stdio Host: Standard I/O extensions
  • Extism WASM Host: Current WASM extensions
  • WASM Component Host: Future WASM Component Model extensions

Benefits of Actor Model

  • Isolation: Each component is an independent actor
  • Concurrency: Parallel processing across actors
  • Supervision: Automatic failure recovery
  • Scalability: Easy to add new protocol types

Migration Path

The current implementation is designed to be compatible with the future actor model:

  1. Current: Direct ExtensionRegistry usage
  2. Future: Extension Manager actor routes requests
  3. Compatibility: Current API can be wrapped in actor messages

Extension Development

See Extension Development Tutorial for how to create extensions.

Next Steps