rylev / wac-example

An example of the wac tool

Wac Example

This repo contains two different but equal ways for composing two example components together

• using the wac CLI
• using the wac-graph library crate

The hello component exports a function hello which returns a string. This will be plugged into the hello import of the greeter component. The resulting component will therefore only have the exported greet function originally from the greeter component.

Note: the hello and greeter components are built with cargo component --target=wasm32-unknown-unknown so the definitions of these component's worlds found in their corresponding wit directories are complete meaning that they do not implicitly import any wasi interfaces.

CLI

wac can be used as a CLI tool. Running the following command should produce a new component that is the composition of the hello and greeter components.

wac encode composition.wac -d example:greeting=world.wit -o composed.wasm  

Note: the -d example:greeting=world.wit is an argument for specifying that the example:greeting wit dependency can be found in the world.wit file.

Programmatic Graph API

You can also build the composition using the programmatic API used by the programmatic example binary. This can be done simply by running the following inside the programmatic directory:

cargo run

Repo Structure

The repo is composed of the following parts:

• build: directory which contains the source code for the two components being composed.
• deps: which contains the build artifacts for the two components being composed (the source for which can be found in build)
• composition.wac: the composition file for performing composition using the wac CLI tool
• programmatic: a Rust binary that uses the programmatic API for composing the two components together in the same way that composition.wac does.