Tinygo - target=wasm results in uncaught promise error in browser console. #4415

owenwaller · 2024-08-16T18:04:43Z

Hi,

Can someone please clarify the level of support provided by tinygo (v0.32.0 - which is the latest AFAIK) with respect to a wasm target that is being executed in a browser, in comparison to Go v1.22.6.

I can currently seeing very different behaviour when I compile a trivial Go file to wasm using both compilers.

When I compile the Go code with tinygo I see the following error message in the browser console:

localhost/:1 Uncaught (in promise) 
TypeError: WebAssembly.instantiate(): Import #1 "wasi_snapshot_preview1": module is not an object or function
Promise.then (async)		
(anonymous)	@	(index):29

However if I compile the same code with Go v 1.226 and server it with the same web server (nginx in a container in my case) the wasm code works as I expect.

Is this a bug in tinygo? I am using the dockerised version of tinygo if that's any help.

Steps to reproduce

main.go

package main

import (
	"fmt"
)

func main() {
	fmt.Printf("Wasm hello\n")
}

index.html

<!doctype html>
<html>
<head>

<title>Wasm Test</title>

<meta charset="utf-8"/>


<script src="https://cdn.jsdelivr.net/npm/[email protected]/lib/encoding.min.js"></script> 
<script src="/wasm_exec.js"></script>
</head>
<body>

<img style="position: absolute; top: 50%; left: 50%;" src="https://cdnjs.cloudflare.com/ajax/libs/galleriffic/2.0.1/css/loader.gif">

</div>
<script>
var wasmSupported = (typeof WebAssembly === "object");
if (wasmSupported) {
	if (!WebAssembly.instantiateStreaming) { 
		WebAssembly.instantiateStreaming = async (resp, importObject) => {
			const source = await (await resp).arrayBuffer();
			return await WebAssembly.instantiate(source, importObject);
		};
	}
	const go = new Go();
	WebAssembly.instantiateStreaming(fetch("/main.wasm"), go.importObject).then((result) => {
		go.run(result.instance);
	});
} else {
	document.getElementById("vugu_mount_point").innerHTML = 'This application requires WebAssembly support.  Please upgrade your browser.';
}
</script>
</body>
</html>

The go.mod is:

module example.com/wasm_http_example

go 1.22.6

The wasm_exec.js is taken from go env GOROOT/misc/wasm/wasm_exec.js`. This is my Go v1.22.6 root.

The tinygo build cmd is:

docker run --rm -v $(pwd):/home/tinygo tinygo/tinygo:0.32.0 tinygo build -o main.wasm -target=wasm main.go

executed in the the directory where the source code is, so the volume map works.

The standard Go build cmd is:

 GOOS=js GOARCH=wasm go build -o main.wasm main.go

Again from the directory that contains the source code.

The resulting main.wasm is then served using a standard nginx container like this:

 docker run --name wasm-nginx --mount type=bind,source=`pwd`,target=/usr/share/nginx/html,readonly -p 8888:80 -d nginx

Again from the directory that contains the source code.

If I serve the main.wasm build with the standard Go v1.22.6 compiler I see Wasm hello in the browser console. If I serve the version built with tinygo I see the uncaught promise error.

This is 100% reproducible, as far as I can tell.

Does anyone have any idea of the cause and is there a fix?

Many thanks

Owen

~~Updated to add: I see the same behaviour is I use Go v 1.23 in comparison to tinggo v0.32.0.~~
So with go 1.23 nothing works. I had a old (read go 1.22.6) module cache locally and an outdated `go.mod that specified go v1.22.6.

If I update the go.mod to:

module example.com/wasm_http_example

go 1.23

I then see this when I attempt to build:

$docker  run --rm -v $(pwd):/home/tinygo tinygo/tinygo:latest tinygo build -o main.wasm -target=wasm main.go
error: requires go version 1.19 through 1.22, got go1.23
owen@carbonx1:/tmp/wasm-http-example$ docker  run --rm -v $(pwd):/go tinygo/tinygo-dev:latest tinygo build -o main.wasm -target=wasm main.go
go: warning: ignoring go.mod in $GOPATH /go
go: go.mod requires go >= 1.23 (running go 1.22.6; GOTOOLCHAIN=local)

$ go version
go version go1.23.0 linux/amd64

$ ls go/pkg/mod/cache/download/golang.org/toolchain/@v/v0.0.1-go1.23.0.linux-amd64.* # from the local `go` directory
go/pkg/mod/cache/download/golang.org/toolchain/@v/v0.0.1-go1.23.0.linux-amd64.lock
go/pkg/mod/cache/download/golang.org/toolchain/@v/v0.0.1-go1.23.0.linux-amd64.zip
go/pkg/mod/cache/download/golang.org/toolchain/@v/v0.0.1-go1.23.0.linux-amd64.ziphash

So that looks like Go v1.23 support isn't in place yet.

Updated to add: if I use the bleeding edge docket image tinygo/tinygo-dev@latest I still see the same uncaught exception error in the browser window. Again against Go v1.23. But in addition I now see this on the command like:

docker run --rm -v $(pwd):/go tinygo/tinygo-dev:latest tinygo build -o main.wasm -target=wasm main.go
go: warning: ignoring go.mod in $GOPATH /go

The warning is new, and as you can see from the docker command the volume mapping now requires mapping into /go on the container (it was /home/tinygo).

The text was updated successfully, but these errors were encountered:

deadprogram · 2024-08-16T18:12:09Z

Make sure you copy wasm_exec.js to your runtime environment.

Via https://tinygo.org/docs/guides/webassembly/wasm/

Also note that the TinyGo wasm_exec.js file is different from the "big Go" file.

Hope that helps!

owenwaller · 2024-08-16T18:56:06Z

@deadprogram

Ah ha, that is indeed the problem. If I swap the wasm_exec.js for the one currently on the master branch:

https://github.com/tinygo-org/tinygo/blob/release/targets/wasm_exec.js

Then all is good using with tinygo v 0.32.0. Well spotted, thank you.

Is there any thing the tinygo team can do to spit this sort of mistake at runtime? Or at least make the error message meaningful?

owenwaller · 2024-08-20T12:46:05Z

Updated to add:

A similar situation exists with the standard Go compiler i.e. the version of wasm_exec.js must match the version of the compiler.

But, given a wasm_exec.js e.g. one that is committed to a repository, it is impossible to tell if that version of wasm_exec.js is compatible with the local Go toolchain.

I have raised this on the golang-nuts mailing list, along with a proposed solution - to embed a version string as a comment into wasm_exec.js See:

https://groups.google.com/g/golang-nuts/c/XJuEayu2KmE

Could the tinygo team please comment on this, and also consider a similar solution, or follow whatever solution to Go project uses?

Thanks

Owen

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Tinygo - target=wasm results in uncaught promise error in browser console. #4415

Tinygo - target=wasm results in uncaught promise error in browser console. #4415

owenwaller commented Aug 16, 2024 •

edited

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deadprogram commented Aug 16, 2024

owenwaller commented Aug 16, 2024

owenwaller commented Aug 20, 2024

Tinygo - target=wasm results in uncaught promise error in browser console. #4415

Tinygo - target=wasm results in uncaught promise error in browser console. #4415

Comments

owenwaller commented Aug 16, 2024 • edited Loading

Steps to reproduce

deadprogram commented Aug 16, 2024

owenwaller commented Aug 16, 2024

owenwaller commented Aug 20, 2024

owenwaller commented Aug 16, 2024 •

edited

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