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Developing/Testing the wasm32 Target

Since there is no native host platform for WebAssembly, developing/targeting requires a bit more setup than a vanilla Rust toolchain environment. To build/target this library outside a wasm-pack context, you can do the following:

  • Install toolchain with wasm32-wasip1 or wasm32-unknown-unknown (e.g. rustup target add wasm32-wasip1).
    • wasm32-wasip1 is a nice target because it gives us the capability to run the tests as-is with a WASM runtime.
  • Install a WASM runtime (e.g. Wasmer/Wasmtime/WAVM).
  • Install wasm-runner a simple runner wrapper to run WASM targeted code with a WASM runtime:
$ cargo install wasm-runner
  • Add a Cargo configuration file to target wasm and allow the unit tests to be run with a WASM VM by default:
[build]
target = "wasm32-wasip1"
rustflags = "-C target-feature=+simd128"

[target.'cfg(target_arch="wasm32")']
runner = ["wasm-runner", "wasmer"]
  • Run the build/tests:
$ cargo test
$ cargo test --all-features

You can do this without configuration as well:

$ RUSTFLAGS="-C target-feature=+simd128" \
    CARGO_TARGET_WASM32_WASI_RUNNER="wasm-runner wasmer" \
    cargo test --target wasm32-wasip1
$ RUSTFLAGS="-C target-feature=+simd128" \
    CARGO_TARGET_WASM32_WASI_RUNNER="wasm-runner wasmer" \
    cargo test --target wasm32-wasip1 --all-features