The state of Wasm in Rust, Haskell, and Go

2023

Haskell

• Use ghc.nix to build a GHC version that targets Wasm
• It supports WASI
• It works on Mac M1

Go

• Go 1.21 added experimental support for WASI (GOOS=wasip1, GOARCH=wasm)
• tinygo: JSON packages now work (tested on 0.29.0)

2022

Compiling to Webassembly (Wasm) is still rather difficult IMO in 2022. Here I document some of my findings:

Haskell

• Compiling to Wasm requires an early release of GHC, slated for GHC 9.6
• It supports WASI
• It does not work on ARM, such as Mac M1

Rust

• The wasm32-unknown-unknown target works, but requires low-level memory management and unsafe blocks
• A bunch of packages like tokio don't work because they transitively depend on net, and WASI doesn't have networking yet (networking is in phase 1 of 5), and it doesn't seem possible to turn off the net feature of transitive dependencies

Go

• The main Go compiler doesn't yet support WASI, it only supports targeting JavaScript environments (see how the only GOOS/GOARCH pair is js/wasm)
• TinyGo supports WASI tinygo build -target wasi ., but a ton of packages like encoding/json don't work because not all of the reflect stdlib package has been implemented in the TinyGo runtime. I tried these alternative JSON packages:
  • ✅ easyjson worked
  • ❌ ffjson failed to compile, last commit 2019
  • ❌ go-codec depends on reflect
  • ❌ fastjson can decode, but can't encode
  • ❌ jsonparser can decode, but can't encode
  • ❌ gabs depends on reflect