zenv | Zenv : Zen Environment - docker based virtual environments | Continuous Deployment library

You are forcing your WatchService to shutdown and recreate every time you poll for events. Since that probably involves some system handles it is likely fairly slow so you would probably missing file events that occur in between. More likely you want to produce the WatchService once and then poll it repeatedly. I would suggest something like this instead:

Error message talks you that you tries to pass to function provide Random.type in the line:

Add -Ypartial-unification to scalacOptions. Lack of this flag is the main offender in Cats, Scalaz, ZIO and type-level-heavy code in general. Or, if you can, migrate to 2.13 where behavior of this flag was changed to be always on (and the flag itself removed).

To parallelize some workload across, say, 8 threads all you need is

Your problem is basically, that you put two effects into single flatMap.

By invoking putStrLn(s) you're not actually printing to console, you're merely creating the description of the action that will print when your program is interpreted and run (when method run is called). And because in your flatmap only last value is returned (in your case UIO.succeed(s)), then only it will be taken into consideration while constructing ZIO program.

You can fix your program by chaining both actions.

You can do it with *> operator:

Let me try to explain.

If you have a look at what ZEnv is it's an alias for Clock with Console with System with Random with Blocking. So, when you started implementing def run(args: List[String]): ZIO[ZEnv, Nothing, Int] zio already provided you with these capabilities.

Your app variable signature has a return type of zio with environment Console with System with Logger - one thing that stands out is a Logger capability. It's not standard so ZIO can't provide it for you. You have to provide it yourself.

That's what you did using .provideSome[Logger] - you eliminated one of the capabilities from environment requirements making it type compatible with the standard:

I would like to explain more but I don't know where you got your code sample or what your build.sbt looks like but I happen to have some http4s code lying around so I took the liberty of adding some import statements and simplifying it a bit. You can always add back the complexity I took out.

Here's what worked for me.