Validation of zip using javascript

Author: jsoriano

code/go-wasm/.gitignore

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+*.wasm

code/go-wasm/Makefile

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+build:
+	GOOS=js GOARCH=wasm go build -o validator.wasm .
+
+test:
+	GOOS=js GOARCH=wasm go test -v -exec="`go env GOROOT`/misc/wasm/go_js_wasm_exec" . ../go/...

code/go-wasm/README.md

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+* Build wasm with `make build`.
+* Run `./validate.js /path/to/package.zip` (or `node validate.js /path/to/package.zip`).
+
+Node.js and Go are required.

code/go-wasm/main.go

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+package main
+
+import (
+	"fmt"
+	"syscall/js"
+
+	"github.com/elastic/package-spec/code/go/pkg/validator"
+)
+
+const moduleName = "elasticPackageSpec"
+
+// asyncFunc helps creating functions that return a promise.
+//
+// Calling async JavaScript APIs causes deadlocks in the JS event loop. Not sure
+// how to find if a Go code does it, but for example ValidateFromZip does, so
+// we need to run this code in a goroutine and return the result as a promise.
+// Related: https://github.com/golang/go/issues/41310
+func asyncFunc(fn func(this js.Value, args []js.Value) interface{}) js.Func {
+	return js.FuncOf(func(this js.Value, args []js.Value) interface{} {
+		handler := js.FuncOf(func(_ js.Value, handlerArgs []js.Value) interface{} {
+			resolve := handlerArgs[0]
+			reject := handlerArgs[1]
+
+			go func() {
+				result := fn(this, args)
+				if err, ok := result.(error); ok {
+					reject.Invoke(err.Error())
+					return
+				}
+				resolve.Invoke(result)
+			}()
+
+			return nil
+		})
+
+		return js.Global().Get("Promise").New(handler)
+	})
+}
+
+func main() {
+	// It doesn't seem to be possible yet to export values as part of the compiled instance.
+	// So we have to expose it by setting a global value. It may worth to explore tynigo for this.
+	// Related: https://github.com/golang/go/issues/42372
+	js.Global().Set(moduleName, make(map[string]interface{}))
+	module := js.Global().Get(moduleName)
+	module.Set("validateFromZip", asyncFunc(
+		func(this js.Value, args []js.Value) interface{} {
+			if len(args) == 0 || args[0].IsNull() || args[0].IsUndefined() {
+				return fmt.Errorf("package path expected")
+			}
+
+			pkgPath := args[0].String()
+			return validator.ValidateFromZip(pkgPath)
+		},
+	))
+
+	// Go runtime must be always available at any moment where exported functionality
+	// can be executed, so keep it running till done.
+	done := make(chan struct{})
+	module.Set("stop", js.FuncOf(func(_ js.Value, _ []js.Value) interface{} {
+		close(done)
+		return nil
+	}))
+	<-done
+}

code/go-wasm/validate.js

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+#!/usr/bin/env node
+
+if (process.argv.length < 3) {
+	console.error("usage: " + process.argv[1] + " [package path]");
+	process.exit(1);
+}
+
+const path = require('path')
+const fs = require('fs');
+
+require(path.join(process.env.GOROOT, "misc/wasm/wasm_exec.js"));
+const go = new Go();
+
+const wasmBuffer = fs.readFileSync('validator.wasm');
+WebAssembly.instantiate(wasmBuffer, go.importObject).then((validator) => {
+	go.run(validator.instance);
+
+	elasticPackageSpec.validateFromZip(process.argv[2]).then(() =>
+		console.log("OK")
+	).catch((err) =>
+		console.error(err)
+	).finally(() =>
+		elasticPackageSpec.stop()
+	)
+}).catch((err) => {
+	console.error(err);
+});