Dealing with host exceptions

[provegard]

I'm having some trouble with host exceptions. Consider the following code:

public class MainEx {
    public static void main(String[] args) {
        Context context = Context.create("js");

        context.getBindings("js").putMember("evil", new Evil());

        String src = "try {\n" +
                "  evil.callMe();\n" +
                "} catch (e) {\n" +
                "  print(e);\n" +
                "  print(e.message);\n" +
                "  print(e.stack);\n" +
                "}";
        context.eval("js", src);
    }

    public static class Evil {
        public void callMe() {
            throw new RuntimeException("boo");
        }
    }
}

It prints:

com.oracle.truffle.api.vm.HostException: boo
undefined
undefined

The problem is that a test framework like Jasmine (and I suppose any other JavaScript code that catches exceptions) tries to access the properties message and stack.

In Nashorn this wasn't a problem, because I could wrap a host exception (I'm in control of nearly all calls from JavaScript) in a custom exception with a getStack method, and getMessage is of course already there. Due to Nashorn's bean-property-access convention, this worked well.

How should I make Graal host exceptions JavaScript compatible?

[provegard]

Note that I'm not using Nashorn compatibility mode. I probably should, but that'll only solve the message property.

[wirthi]

Hi provegard,

thanks for your report. We need to discuss that internally. I currently know of no way to access the original exception from JavaScript code, Truffle always wraps the exception in a HostException what is not overly helpful to you.

CC @chumer

[provegard]

Thank you!

Note that the fact that there is a HostException that wraps the original exception needs to be an implementation detail; Jasmine calls e.message and e.stack, so exposing the original via something like e.getOriginal() is also not useful.

[wirthi]

@woess has pushed a fix to expose the host exception directly. This should solve your problem.

I am closing this, please reopen if the problem persists.

-- Christian

[provegard]

In which release?

Do you mean that the code I posted will print message and stack?