Add integration for 'multipleResolves' event

[iatsiuk]

• Review the documentation: https://docs.sentry.io/
• Search for existing issues: https://github.com/getsentry/sentry-javascript/issues
• Use the latest release: https://github.com/getsentry/sentry-javascript/releases

Package + Version

• @sentry/browser
• @sentry/node
• raven-js
• raven-node (raven for node)
• other:

Version:

@sentry/node@4.5.1

Description

The 'multipleResolves' event is emitted whenever a Promise has been either:

• Resolved more than once.
• Rejected more than once.
• Rejected after resolve.
• Resolved after reject.

Node.js v11.6.0 Documentation link.

[HazAT]

We happily accept PRs for this :)

[iatsiuk]

I don't know TypeScript, sorry for that.

I'm using this snippet for now:

process.on('multipleResolves', async (type, promise, value) => {
  let originalVal;

  try {
    originalVal = await promise;
  } catch (err) {
    originalVal = err.stack && err.message ? err.message : err;
  }

  const swallowedVal = value.stack && value.message ? value.message : value;
  const multipleResolvesError = new Error(
    [
      `Swallowed promise ${type}`,
      `original value: ${JSON.stringify(originalVal)}`,
      `swallowed: ${JSON.stringify(swallowedVal)}.`
    ].join(', ')
  );

  Sentry.captureException(multipleResolvesError);
});

[HazAT]

This is already really helpful, thanks 💯
When we find some time we will implement a pluggable integration for this.