draft: synchronousTransformIterator

[jeswr]

As discussed in https://github.com/RubenVerborgh/AsyncIterator/pull/75#issuecomment-1168219877.

TODOs

• Add more coverage
• See if https://github.com/RubenVerborgh/AsyncIterator/blob/3a5b62cf8ca00e60013b6aa7c1e692b26fcb6964/asynciterator.ts#L905-L911 is necessary. @RubenVerborgh the question here is - can we just assume the root is .readable if the parent source is .readable. If we assume that all of the intermediary sources are SynchronousTransformIterators as is the case when doing chaining then this will be true; but I am not sure if we should be making this assumption.

Quick testing indicates that this results in a ~2x performance increase on the tests in #75

[jacoscaz]

Should this be a part of the changes summarized at https://github.com/RubenVerborgh/AsyncIterator/issues/44#issuecomment-1166907641 ?

[jacoscaz]

@jeswr is this something you're still working on? Would this be releasable as 3.x or 4.x?

[jeswr]

@jacoscaz The changes are still valid - and there are no breaking changes. I can try and work on the test coverage over the weekend depending on my time (though I'm looking a bit stretched thin at this point).

[jacoscaz]

No pressure or rush meant! Just checking, I was having a look at updating my summary in #44 and wasn't sure about this one. Nice!