None.get on nested case class mapping

[greenhost87]

Simple code to reproduce error on last Slick 3.2.1 version:
https://github.com/snap-swap/slick-none-get-exception

Example code is: https://github.com/snap-swap/slick-none-get-exception/blob/master/src/main/scala/com/snapswap/slick/SlickNoneGetError.scala

If you run code you get exception:

Exception in thread "main" java.util.concurrent.TimeoutException: Futures timed out after [10 seconds]
	at scala.concurrent.impl.Promise$DefaultPromise.ready(Promise.scala:219)
	at scala.concurrent.impl.Promise$DefaultPromise.result(Promise.scala:223)
	at scala.concurrent.Await$$anonfun$result$1.apply(package.scala:190)
	at scala.concurrent.BlockContext$DefaultBlockContext$.blockOn(BlockContext.scala:53)
	at scala.concurrent.Await$.result(package.scala:190)
	at com.snapswap.slick.SlickNoneGetError$.delayedEndpoint$com$snapswap$slick$SlickNoneGetError$1(SlickNoneGetError.scala:72)
	at com.snapswap.slick.SlickNoneGetError$delayedInit$body.apply(SlickNoneGetError.scala:12)
	at scala.Function0$class.apply$mcV$sp(Function0.scala:34)
	at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
	at scala.App$$anonfun$main$1.apply(App.scala:76)
	at scala.App$$anonfun$main$1.apply(App.scala:76)
	at scala.collection.immutable.List.foreach(List.scala:381)
	at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:35)
	at scala.App$class.main(App.scala:76)
	at com.snapswap.slick.SlickNoneGetError$.main(SlickNoneGetError.scala:12)
	at com.snapswap.slick.SlickNoneGetError.main(SlickNoneGetError.scala)

Interesting thing: if option field error setted no error happens (insert a1 as example), but if that field is empty code ruins with error.

As work around you can introduce some of Database Object (DO) and then cover your nested model object to flat DO case class.

[d6y]

Hello @greenhost87 - thanks for the example.

It looks to me like your mapping function needs to return Some(None) on line 34.

However, there's a good case that the meaning of that R => Option[U] function should be explained in the manual. It's not clear what returning None could mean.

As an alternative, you might be able to use:

case class ErrorInfo(value: String) extends MappedTo[String]

...and then preserve the ErrorInfo tpe you want in the column:

def errorCode = column[Option[ErrorInfo]]("error_code")

...and then directly reference errorCode in your projection:

def * = (id, `type`, errorCode).mapTop[Action]

[greenhost87]

@d6y Thank, add Some(None) fixing the problem, but it's totally unclear why :), for strong type safe mapping. like Slick, this case need more clear way to solve.

Alternative way is work, but if you have only one model. without separation DO and Application models, your whole application begin know about slick mapping specific things.

[d6y]

Thanks for confirming that @greenhost87. I'll leave this ticket open as a note to improve the documentation.

In case it helps regarding the alternative, you can separate the mapping from the model. E.g.,

object adapters {
  implicit val errorInfoMapper = 
     MappedColumnType.base[ErrorInfo, String](_.code, ErrorInfo.apply) 
}

And then import adapters._ where you need them.

[d6y]

What I think would help here is an explanation of why <> has a second argument of a function to Option[T], and what it means if that is None.