wasm/

WASM Island ABI

This example shows the supported component-level WASM island package shape.

component WasmCounter
wasm ./examples/components/wasm/browser/counter

The browser Go package is a normal package main compiled with GOOS=js GOARCH=wasm. It must export the component-scoped ABI functions with //go:wasmexport:

//go:wasmexport GOWDKMountWasmCounter
func GOWDKMountWasmCounter() uint32 { return 0 }

Build It

Run from the repository root:

go run ./cmd/gowdk build --out /tmp/gowdk-wasm-island examples/components/wasm/*.gwdk
test -f /tmp/gowdk-wasm-island/components/wasm/index.html
test -f /tmp/gowdk-wasm-island/assets/gowdk/islands/componentwasm/WasmCounter.wasm
test -f /tmp/gowdk-wasm-island/assets/gowdk/islands/componentwasm/WasmCounter.wasm.js
test -f /tmp/gowdk-wasm-island/assets/gowdk/islands/wasm_exec.js

The current ABI validates required exports and browser-safe imports, emits the host loader, and reports unsupported patch operations in the browser console. User Go patch-memory decoding beyond the current uint32 return contract is still planned.

Page stores

A WASM island that declares use <store> in its client block participates in page stores like a JS island. The host loader:

• reads every used store and merges its current (and persisted) value into the state field of the mount/handle/destroy payload, and passes the used store names in payload.stores;
• writes back when an export returns the extended result shape { "patches": [...], "stores": { "<name>": <value> } } — each returned store value is written to window.__gowdkStores. The legacy bare patch array is still accepted (no store write-back);
• syncs on external changes: when another island updates a used store, the loader re-invokes the mount export with the refreshed state and applies the returned patches, without echoing the update back into the registry.

Surfacing serialized state from the uint32 export contract (so a Go island can return the stores map) is the remaining Go-side ABI work tracked alongside the patch-memory decoding above.