alexarchambault/scalacheck-shapeless

Generation of arbitrary case classes / ADTs with scalacheck and shapeless

Olli Helenius

@liff

is it possible/useful to explicitly materialize Arbitrary instances? this doesn't work for some reason

i'm hoping, by using explicit instances, it'd compile a bit faster maybe?

wedens

@wedens

org.scalacheck.derive.MkArbitrary[A].arbitrary

Olli Helenius

@liff

oh ok, thanks a lot

Cause Chung

@cuzfrog

@alexarchambault Is there any way to provide a non-empty arbString to substitute the string scalacheck-shapeless uses to gen class?

Simon Hafner

@reactormonk

@cuzfrog regular implicit replacement.

Cause Chung

@cuzfrog

@reactormonk thanks

Albert Serrallé Ríos

@aserrallerios

Hi all!

just a simple question

case class B(i:Int)
case class A(b:B)
implicit val _ = Arbitrary(implicitly[Arbitrary[B]].arbitrary.filter(_ == 0)))
val a = implicitly[Arbitrary[A]]

should a only generate B(0) instances?

Albert Serrallé Ríos

@aserrallerios

sorry guys, it's working

my problem was that I was not providing implicit instances of Arbitrary, but implicit instances of Gen :thumbsup:

Howy Perrin

@howyp

@alexarchambault Thanks for merging #77 , any idea when the next release might be?

Alexandre Archambault

@alexarchambault

@howyp I'll do a release after these few more updates: alexarchambault/scalacheck-shapeless#78.

Howy Perrin

@howyp

Great, thanks

Alexandre Archambault

@alexarchambault

Doing a release slipped my mind, will try to do it today if I can get my gpg keys from where I am right now…

Alexandre Archambault

@alexarchambault

@howyp 1.1.8 is out!

Howy Perrin

@howyp

🎉

Thanks!

Luciano

@lJoublanc

Morning. Does scalacheck-shapeless provide any sort of automatic coproduct generation? E.g. if I have a sealed trait, can I just do Arbitrary[MyTrait] and have it return it's subclasses?

Olli Helenius

@liff

@lJoublanc like this?

Luciano

@lJoublanc

exactly!

Would this work with Arbitrary[A :+: B :+: C] too, do you know?

I'll try it out.

Luciano

@lJoublanc

yeah that doesn't work :( trying to do Arbitrary[Int :+: Long]. On the other hand Arbitrary[AnyVal] does work, but I get lots of stuff I don't want (Unit) for example.

Georgi Krastev

@joroKr21

There is definitely an Arbitrary for Coproducts somewhere in there, maybe it's just not exposed. Look around the source code.

found it - MkCoproductArbitrary

Luciano

@lJoublanc

Thanks @joroKr21 will check it out today.

Marko Dimjašević

@mdimjasevic

Hi everyone!

I'd like to generate sequences of valid state machine transitions. Any idea how to do this with scalacheck-shapeless? I was thinking of using IndexedStateT from https://github.com/typelevel/cats/blob/master/core/src/main/scala/cats/data/IndexedStateT.scala to encode an input and output state of a transition.

Ihor Kaharlichenko

@kaharlichenko

Hi. Is there any way I could customize the generator for a case class? Suppose I have case class Person(name: String, age: Int) and I want age to be generated as Gen.posNum, while the rest of the field generators being derived?

Olli Helenius

@liff

@kaharlichenko well if you have arbPerson: Arbitrary[Person] you could do something like:

implicit val properArbPerson: Arbitrary[Person] = Arbitrary(arbPerson.arbitrary.flatMap(person => Gen.posInt.map(age => person.copy(age = age))))

alternatively you could create a distinct type for age, possibly with refined, newtype or otherwise. then you could just create an arbAge: Arbitrary[Age] and not worry about how a Person is generated

Ihor Kaharlichenko

@kaharlichenko

Well, changing the type of age is not an option, since that would involve changing the production code for the sake of testing. The second option is viable, though. Thank you.

Jason Pickens

@steinybot

Do the generated Arbitrarys ignore other implicits in scope? I haven’t been able to confirm or deny yet but it seems to be the case. For example:

case class Foo(bar: Bar)
implicit val arbBar: Arbitrary[Bar] = somePredefinedArbitraryForBar // This is not used
implicit val arbFoo: Arbitrary[Foo] = MkArbitrary[Foo].arbitrary

Jason Pickens

@steinybot

may have been a PBKAC error

Jason Pickens

@steinybot

Does the library work with recursive types?

I’m getting a StackOverflowError but it might just be me again

Paul Snively

@PaulAtFormation

Could someone please offer an example of generating a Shapeless Coproduct, presumably using the aforementioned MkCoproductArbitrary? I'm getting:

could not find implicit value for parameter mkArb: org.scalacheck.derive.MkCoproductArbitrary[takt.data.valkyrie.deployables.etl.VAL1081.ValkyrieType]

Alex

@unthingable

Hello. How does one confine generated String vals for a given case class to non-Unicode characters?

Daniel Sebban

@dsebban

Hi I am getting at runtime

ava.lang.IllegalArgumentException: requirement failed: Duration is limited to +-(2^63-1)ns (ca. 292 years)
[info]  at scala.concurrent.duration.FiniteDuration.<init>(Duration.scala:583)
[info]  at scala.concurrent.duration.Duration$.apply(Duration.scala:31)
[info]  at scala.concurrent.duration.package$DurationLong$.durationIn$extension(package.scala:48)
[info]  at scala.concurrent.duration.package$DurationLong.durationIn(package.scala:48)

is there a way to override the Duration generator implicit with a correct one

Gabriel Assis Bezerra

@gabriel-bezerra

as far as I know, the Arbitrary[T]s in scope are preferred instead of the derived ones

import /*the automatic derivation from the library*/

implicit val arbitraryDuration: Arbitrary[Duration] = ...

implicitly[Arbitrary[SomethingThatNeedsDuration]] // this should use arbitraryDuration

Luciano

@lJoublanc

Was just about to post practically the same question as above ... I have:

case class Dense[K: Field](layout: Layout, stride: Int)

but if I put an implicit val stride: Arbitrary[Int] = ... before forAll, in order to limit the values of stride, it's not being picked up. It sounds like the same problem as above?

Luciano

@lJoublanc

@dsebban how did you finally resolve your issue?

Luciano

@lJoublanc

Ah figured it out - it's the old 'shrink' problem ...

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