Building Golem Components in Rust

Building Golem components written in Rust is a single call of the cargo component build command:

$ cargo component build
Generating bindings for example (src/bindings.rs)
 Compiling example v0.1.0 (/Users/vigoo/tmp/doc-temp/example)
 Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.33s
 Creating component target/wasm32-wasi/debug/example.wasm

The target/wasm32-wasi/debug/example.wasm file is a WebAssembly component ready to be uploaded to Golem.

It is recommended to compile a release build of the component before deploying it to Golem as it is more optimized and smaller in size:

$ cargo component build --release
Generating bindings for example (src/bindings.rs)
 Compiling example v0.1.0 (/Users/vigoo/tmp/doc-temp/example)
 Finished `release` profile [optimized] target(s) in 0.33s
 Creating component target/wasm32-wasi/release/example.wasm

⚠️

Make sure the Creating component ... line is printed. Some previous versions of cargo-component failed silently in some cases, skipping the last part of packaging the built WebAssembly module into a component.

It is possible to verify that the result .wasm is a valid WebAssembly component by using the wasm-tools CLI tool and running:

$ wasm-tools print target/wasm32-wasi/release/example.wasm --skeleton

The top-level node must be component and not module.

IDE support

Any IDE supporting Rust can be used, however for creating the result WASM file, the cargo component build command must be used instead of the usual cargo build command that the IDE might use under the hood.

When using rust-analyzer, read the following section of the cargo-component documentation about how to configure it properly: https://github.com/bytecodealliance/cargo-component#using-rust-analyzer (opens in a new tab)

Defining Components Next Steps