Little Finch/Circe app, that shows how to get None not being emitted as Null

FinchRestWithNoNulls.scala

import cats.effect.IO
import com.twitter.app.Flag
import com.twitter.finagle.http.{Request, Response}
import com.twitter.finagle.{Http, ListeningServer, Service}
import com.twitter.server.TwitterServer
import com.twitter.util.Await

import io.finch.catsEffect._

import io.finch._
import io.finch.circe.dropNullValues._
import io.circe.generic.auto._

object FinchRestWithNoNulls extends TwitterServer  {

  final case class Foo(id: String, op: Option[String]=None)

  def getFooList(a:String = "")= List(Foo("1", Option("hello")), Foo("2"))

  val fooListApi: Endpoint[IO, List[Foo]] = get("v1" :: "foos" ) {
    Ok(getFooList())
  }

  // Finch-finagle service
  val apiService: Service[Request, Response] = Bootstrap.
    //serve[Application.Json](fooApi).toService
  serve[Application.Json]    (fooListApi).toService

  val port: Flag[Int] = flag("port", 8081, "TCP port for HTTP server")

  def main(): Unit = {
    val server: ListeningServer = Http.server.serve(s":${port()}", apiService)
    println("Listening: " + port() )
    onExit { server.close() }
    Await.ready(adminHttpServer)
  }
}