Improve stack traces for port errors

[rtfeldman]

Suppose we have a bad port invocation that's going to blow up, in a file called index.html:

function invokeBustedPort() {
  app.ports.foo.send(null);
}

// alternatively, for a post-init error: setTimeout(invokeBustedPort, 500);
invokeBustedPort();

Before

The stack trace doesn't include the offending function, invokeBustedPort, or a useful line number indicating where the function was invoked:

After

Now it includes both!

What Changed

The basic idea is to do the decoder check immediately inside send, and throw new Error inside send so it preserves the best stack trace information.

This means that in the preInit case it fails slightly sooner, because it does the check before init - and then defers the actual value sending - instead of deferring both.

[process-bot]

Thanks for the pull request! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[process-bot]

Thanks for the pull request! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[turboMaCk]

This is great! I was dealing with this week ago. This improvement will make it much easier. 👍

[turboMaCk]

This is great! I was dealing with this week ago. This improvement will make it much easier. 👍

[evancz]

Makes sense to me, nice improvement!

[evancz]

Makes sense to me, nice improvement!