opa wasm example

README.md

1. put example_main.go in example/main.go in an OPA checkout
2. compile via Go: GOOS=js GOARCH=wasm go build -o example.wasm ./example/
3. Use with wasm_exec.js, and some index.html
4. call opa.parse("package foo") in the browser's dev tools console

example_main.go

package main

import (
	"syscall/js"

	"github.com/open-policy-agent/opa/ast"
	"github.com/open-policy-agent/opa/format"
)

func main() {
	done := make(chan struct{})
	js.Global().Set("opa", make(map[string]interface{}))
	module := js.Global().Get("opa")
	module.Set("parse",
		js.FuncOf(func(this js.Value, args []js.Value) interface{} {
			if args == nil {
				panic("initialize: not enough args")
			}

			mod, err := ast.ParseModule("a.rego", args[0].String())
			m := map[string]interface{}{}
			if err != nil {
				m["error"] = err.Error()
			} else {
				m["result"] = formatMod(mod)
			}
			return m
		}),
	)

	<-done
}

func formatMod(m *ast.Module) string {
	out, err := format.Ast(m)
	if err != nil {
		panic(err)
	}
	return string(out)
}