AVA unhandled exceptions patch should be accomplished in userspace

[michaelfig]

What is the Problem Being Solved?

agoric-sdk/packages/internal/src/lib-nodejs/ava-unhandled-rejection.js uses a subprocess and agoric-sdk/patches/ava+5.3.1.patch to isolate the test and then be able to expect a count of how many unhandled rejections it creates without crashing AVA.

Description of the Design

While the subprocess is still a good idea to prevent cross-contamination of unhandled rejections, @gibson042 had suggestions for how the subprocess could use the process.on events to count and handle rejections.

We could adopt the same algorithm from SES for unhandled rejections (only marking a rejection as unhandled upon GC of the Promise). That way, the tests won't be sensitive to the SES configuration itself.

This would be a modification just to the internals of ava-unhandled-rejection.js.

Security Considerations

Test code only.

Scaling Considerations

n/a

Test Plan

The point.

Upgrade Considerations

None.

[michaelfig]

From @gibson042 : fail the test if an unhandled rejection doesn't happen

  const unhandled = new Set();
  const onUnhandled = (_reason, p) => {
    unhandled.add(p);
  };
  const onHandledLate = p => {
    unhandled.delete(p);
  };
  process.on('unhandledRejection', onUnhandled);
  process.on('rejectionHandled', onHandledLate);
  t.teardown(() => {
    process.off('unhandledRejection', onUnhandled);
    process.off('rejectionHandled', onHandledLate);
  });

  // …remainder of test body…

  t.true(unhandled.size > 0);