Better error message when module is not linked.

[stroiman]

In my code, I call

mod, err := sobek.ParseModule( ... )
mod.Evaluate(vm)

The code results in a nil panic in vm.go:639, which goes away if I call mod.Link()

func (vm *vm) run() {
	// ...
	for {
		// ...
		pc := vm.pc
		if pc < 0 || pc >= len(vm.prg.code) { // <- nil pointer panic here
			break
		}
		// ...
	}

	// ...
}

Perhaps a more helpful error message would be nice?

[mstoykov]

Hi @stroiman, glad that you are still going on this.

The API (as mentioned in other places) is basically what the specification says it is ... with small changes to make it go compatible. And is far from very easy to use (as you've noticed). I have not had the time to try to make it more ergonomic, and it likely will need to wait until a change in the specificaiton to modules taht requires a lot of other work as well.

Having said that, I think in this case we can return some error from Evaluate and check that the source module has a program before continuing. We can not (or at least will be bad to ) change the API so we will have to error through the promise.

If you have time I do welcome PRs 😅

[stroiman]

we can return some error from Evaluate

I think that would be helpful ;)

Btw, I do have a working prototype with sobek and ESM support. Needs a bit of cleanup before release.