handle unpipeing, cancelling or destroying of busboy accordingly

[Uzlopak]

Should fix fastify/fastify-multipart#315

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[kibertoad]

Yes, it does look like the right solution. Can we cover it with tests though?

[Uzlopak]

tbh I have no idea how to simulate an aborted upload.

[Uzlopak]

Do you have any idea how to implement it?

[mccare]

Looking through the tests, I would do it similar to the multipart-pause (

busboy/test/multipart-stream-pause.spec.js

Line 76 in 6d8f874

reqChunks.forEach(function (buf) {

)

Btw, would you need to clear the event listener on busboy after the file has been succesfully processed?

[mcollina]

Any update on this one?

[kibertoad]

I can try adding the test in a day or two if @Uzlopak doesn't do it first.

[Uzlopak]

If you call destroy again, it is handled as a no-op. https://nodejs.org/api/stream.html#writabledestroyerror
So it is no problem to destroy it again.

Regarding the removal of the listener: Does it really matter? It either fails totally or it succeeds together. We dont pass an error object to destroy, so destroying the busboy-stream after we processed everything should not result in any additional errors. So if the FileStream got piped and processed it can be savely destroyed, imho.

[Uzlopak]

So what is now with this PR?