Composable Factory

Build Wasm Components with Wasm Components

(Work-in-Progress)

The API

A factory is a component that emits another component. You implement ComponentBuilder:

impl ComponentBuilder for Builder {
    fn build_world(&self, world: &mut World) -> Result<()>;
    fn build_function(&self, function: &ExportedFunction, imports: &Imports) -> Result<()>;
}

build_world declares the generated component's surface.

build_function is then called once per exported function to emit its body.

Examples

• calculator: a factory that generates a 4-function calculator, emitting Wasm instructions directly.
• logging-interceptor: a factory that mirrors an arbitrary target component's exports, forwards to them as imports, and logs each call and return.

License

Copyright (c) 2026 Modulewise Inc and the Composable Factory contributors.

Apache License v2.0: see LICENSE for details.