Promise callback with queryConfig options.

[nmaves]

Resolves #335

When you execute a PG query with an QueryConfig object the implicit promise callback is the 3 element in the args.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[willarmiros]

Thanks for the contribution @nmaves! Any chance you could add a unit test to verify this behavior when capturing a query with a promise-based callback? Also, what would the 2nd argument be then in this case?

[nmaves]

Honestly, I am not sure how to write this with your current test setup.

From my testing that second argument is null. I put in debug statements with your code and found that to be the case.

[willarmiros]

That's fair enough, I'd be fine with not having a unit test here if there was some validation to check if the 3rd argument is a function. Something similar to what we already do on L45: https://github.com/aws/aws-xray-sdk-node/blob/master/packages/postgres/lib/postgres_p.js#L45

[nmaves]

Does that work?

[willarmiros]

Looks like the test is failing because you need to include argsObj[0].callback instead of undefined as the final fallback possibility to match the original behavior.

[nmaves]

The test is now passing.

[willarmiros]

Great, thanks again for the changes!

[nmaves]

hey @willarmiros you guys think you might snap a release anytime soon to get this out in the wild?

[willarmiros]

We're definitely due for a release, I'll prioritize one soon. Thanks for the ping @nmaves !

[nmaves]

@willarmiros don't make me beg and look like a need open source abuser :)