upgrade leveldown and fix iterator problems

[ralphtheninja]

Closes #6551

I was a bit unsure on where to check for the error. We have different options here.

At first I wanted to put an error handler on changeStream here, which could check for that particular error. But unclear to me how a different error should be handled. changeStream is also completely internal to the api._changes function so a bit clunky to handle the errors.

So I tried to go deeper instead and try to stop this error as early as possible and as close to iterator.next(cb) as possible and basically don't even emit it on the stream to begin with.

Let me know if you aren't happy with this solution and/or if it should be tweaked.

Cheers

[ralphtheninja]

I have no idea about some of the errors. Might some of them be related to other things?

Apparently tests did work. Guessing someone restarted them :)

[daleharvey]

Ignoring this based on the string of an error message is quite fragile, it would be nice to be a little more robust and only ignore errors when we know for example the iterator died after we closed the db, or preferably to close the iterator ourselves.

However very happy to have this unblocked and us back to receiving leveldown updates, its a large complex dep and we dont want to get stuck too far back, happy to merge this and we can look at being little more robust / cleaner as we go on.

Thanks so much at looking into this and dealing with the complexities of the pouch test suite, I know its pretty hairy :)

[daleharvey]

And yup, the failing tests werent level related and can be a bit flaky, trying to get them more stable but occasionally need a restart

[ralphtheninja]

Ignoring this based on the string of an error message is quite fragile, it would be nice to be a little more robust and only ignore errors when we know for example the iterator died after we closed the db, or preferably to close the iterator ourselves.

@daleharvey Aye, I was thinking exactly the same. I was thinking we could clean that up later by e.g. named errors in e.g. level/errors that abstracts it better. But currently only levelup uses the error module and not leveldown so that has to be changed.

[ralphtheninja]

@daleharvey What do you reckon the new version is going to be? A patch?

[ralphtheninja]

Nevermind, I'm an idiot :) https://github.com/pouchdb/pouchdb/blob/master/package.json#L3

[ralphtheninja]

No wait, that version is not correct either haha. Ok, I think I got it now. Next version will be 6.3.5.

[holsted]

Any update on when this might land in the next version @daleharvey?