Simple WASM Runner

This is a simple wrapper program to run a WASM runtime (currently one of wasmer or wasmtime) as a runner for things like cargo run. This is useful when wanting to use a target such as wasm32-wasi without the trappings of wasm-pack for example, just running cargo run or cargo test in a package for the wasm32-wasi target. Cargo expects a runner to take the program executable followed by its arguments, and most WASM runtimes have a particular structure to their arguments (e.g., requiring a -- before program arguments).

Usage

Install the runner using cargo: $ cargo install wasm-runner

You can install directly from the source tree as: $ cargo install --path=.

After this you can now have a .cargo/config.toml that uses this runner to execute your binaries for WASM targets.

For example: [target.'cfg(target_arch="wasm32")'] runner = ["wasm-runner", "wasmer"]

This assumes wasmer is in your PATH, but you can also specify the full path if you like.

At this point assuming wasm32-wasi is installed as a target in your toolchain (e.g., rustup target add wasm32-wasi), you can run unit tests or binaries with: $ cargo --target wasm32-wasi test $ cargo --target wasm32-wasi run -- some arguments

The WASM_RUNNER_VERBOSE environment variable can be set to get diagnostic output as to what the runner is doing.

Sample Application

The test-wasm folder has a simple crate that is configured to run the wrapper with wasmer. $ (cd test-wasm && cargo run --verbose -- hello world)

TODO

• CI testing for wasmtime.
• Ability to customize runtime arguments via environment variables.
• Ability to support other runtimes such as wavm.

License

This project is licensed under the Apache-2.0 License.