events: support dispatching event from event

[benjamingr]

Currently our events guard against dispatching an event from itself by type rather than by event instance. This makes a WPT test fail.

Here's some code to demonstrate the issue.

{
  const target = new EventTarget();
  const event = new Event('foo');
  let callCount = 0;
  target.addEventListener('foo', (() => {
    callCount++;
    if (callCount < 5) {
      target.dispatchEvent(new Event('foo'));
    }
  }, 5));
  console.log(callCount)
}

Dispatching an event while handling it is still not supported (as required).

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

[benjamingr]

@jasnell I think you might have missed this one :]

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/31654/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/31680/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/31766/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/31825/

[jasnell]

Ping @benjamingr ... tests are failing on this one.

[benjamingr]

@jasnell sorry, I was (mostly) AFK and am (mostly) AFK for the coming week (except the summit). I will do one pass over all the PRs you pinged me at and fix/rebase them over master.

I feel like this landing part is harder than it should so feel free to either squash them all into one PR and land it as one change, or to just make all the changes directly (I really don't mind the git attribution being precise) or whatever is most convenient to you.

Again: my objective is to be helpful and to do the least toe-stepping :]

[jasnell]

@benjamingr ... yeah, it's been pretty painful doing these piece by piece. I think I'll go ahead and combine all the changes into a single PR.

[benjamingr]

@jasnell I am starting to see what you meant by "take it to a vendored dep" back then :]

Anyway, whatever is easiest and least painful for you. Another thing we can do is open one PR that will stay open for a few days on a branch, then we can push all the changes to that branch and merge that after a few days or something.

[jasnell]

Closing in favor of #34015 (which combines this and other eventtarget PRs into a single to make landing easier