Streams hang when converting fs2 -> zio -> fs2 + map

[adamw]

We're debugging hanging websocket tests as part of softwaremill/tapir#2043 (things work fine w/ zio1, stop working when updating to the latest RCs of zio2).

I think I minimised the problem to the following:

import zio.Task
import zio.stream.interop.fs2z._
import zio.interop.catz._

import scala.concurrent.duration.DurationInt

object Test extends App {
  val input: fs2.Stream[Task, String] = fs2.Stream[Task, String]("abc") ++
    fs2.Stream.awakeEvery[Task](1.second).map { _ =>
      println("PRODUCING"); "xyz"
    }

  zio.Runtime.global.unsafeRunToFuture(input.toZStream().toFs2Stream.map(x => x).compile.drain)
}

When this is run, nothing gets printed to the console. Removing .toZStream().toFs2Stream or, interestingly, .map(x => x), causes PRODUCING to be printed out in the expected intervals.

[adamgfraser]

@adamw Hmmm, the above code prints out PRODUCING in the expected intervals when I run it on zio2-interop-ce3.

[adamw]

Hm what's zio2-interop-ce3? :) I'm using "dev.zio" %% "zio-interop-cats" % "3.3.0-RC5"

[adamw]

Ah it's a branch name ... let me checkout the project

[adamw]

@adamgfraser So it indeed works on zio2-interop-ce3 branch, however the fs2 and cats-effect versions are outdated. I tried upgrading to fs2 3.2.7 (from 3.0.6) but the project stopped compiling. Also, cats effect is now at 3.3.11 instead of 3.2.9.

[adamw]

(my suspicion being that things stop working when using latest fs2/cats-effect :) )

[adamgfraser]

Aren't these versions supposed to be binary compatible?

[adamw]

@adamgfraser no idea :) apparently at least fs2 is not ;)

[adamgfraser]

Looks like this was broken in fs2 version 3.1.1.

[gavares]

Is this a bug in fs2 or a bug in this library?

[adamw]

@adamgfraser Works, thanks a lot for the fix & fast release! :)

[adamgfraser]

@adamw Awesome! 😃