`fs2.io.readOutputStream` doesn't preserve errors from `cats.data.EitherT`
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bug
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- Scala
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Description
Using the latest fs2 version 3.7.0 and an effect type that includes cats.data.EitherT, an error in the effect is not preserved when using fs2.io.readOutputStream. Possibly related to #2821
Minimized reproduction:
https://scastie.scala-lang.org/mrdziuban/qLvScG5BSWiLsXlhB5pJYg/2
import cats.data.EitherT
import cats.effect.IO
import cats.effect.unsafe.implicits.global
type Eff[A] = EitherT[IO, String, A]
fs2.io.readOutputStream[Eff](1024)(_ => EitherT.left(IO.pure("error")))
.compile
.drain
.value
.unsafeRunSync()
// Right(())
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with the minimized Scala reproduction and the fs2.io.readOutputStream entry point, then trace how the EitherT effect is compiled and drained. Verify the behavior against the reproduction: the Left("error") result should be preserved instead of producing Right(()).
Written by the indexing model from the issue text.
Assessment
- Tech stack
- scala
- Domain
- stream-processing
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 42/100