Create Java Collections module

[MateuszKubuszok]

• turn chimney-java-collections into publishable module
• create instances for Java collections
  • java.util.Optional
    • test for total
    • test for partial
  • java.util.Iterable
    • test for total
    • test for partial
  • java.util.Enumeration
    • test for total
    • test for partial
  • java.util.Collection
    • test for total
    • test for partial
  • java.util.BitSet
    • test for total
    • test for partial
  • java.util.Dictionary
    • test for total
    • test for partial
  • java.util.Map
    • test for total
    • test for partial
  • java.util.Properties
    • test for total
    • test for partial
  • java.util.stream.Stream
    • test for total
    • test for partial
• test that conversions produce correct error messages for partials
• create Java collections documentation

[codecov]

Codecov Report

Attention: 17 lines in your changes are missing coverage. Please review.

Comparison is base (8ae8524) 84.27% compared to head (49b91b2) 85.86%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #391      +/-   ##
==========================================
+ Coverage   84.27%   85.86%   +1.58%     
==========================================
  Files         108      117       +9     
  Lines        4071     4463     +392     
  Branches      182      171      -11     
==========================================
+ Hits         3431     3832     +401     
+ Misses        640      631       -9     

Files	Coverage Δ
...nd/chimney/javacollections/JavaFactoryCompat.scala	100.00% <100.00%> (ø)
...s/JavaCollectionsPartialTransformerImplicits.scala	100.00% <100.00%> (ø)
...ons/JavaCollectionsTotalTransformerImplicits.scala	100.00% <100.00%> (ø)
...ollections/internal/PartialTransformOrUpcast.scala	100.00% <100.00%> (ø)
...y/javacollections/internal/TransformOrUpcast.scala	100.00% <100.00%> (ø)
...nd/chimney/javacollections/JavaFactoryCompat.scala	87.50% <87.50%> (ø)
...nd/chimney/javacollections/JavaFactoryCompat.scala	75.00% <75.00%> (ø)
...alaland/chimney/javacollections/JavaIterator.scala	88.23% <88.23%> (ø)
...calaland/chimney/javacollections/JavaFactory.scala	96.49% <96.49%> (ø)

... and 10 files with indirect coverage changes

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[MateuszKubuszok]

I am not entirely happy with the amount of implicits I have to write and that I cannot create JavaIterable[A, CC] similarly to JavaFactory to abstract over all possible iterations, since I get a lot of ambiguity errors that didn't happen with JavaFactory. For instance:

trait JavaIterator[CC] {
  type A

  def foreach(collection: CC)(f: A => Any): Unit
}
object JavaIterator {

  type Aux[A0, CC] = JavaIterator[CC] { type A = A0 }

  implicit def iterator[A]: Aux[A, java.util.Iterator[A]] = ???

  implicit def bitSet: Aux[Int, java.util.BitSet] = ???

  implicit def iterable[A, CC <: java.lang.Iterable[A]]: Aux[A, CC] = ???

  locally {
    import io.scalaland.chimney.PartialTransformer

    implicit def partialForJavaToJava[JColl1, JColl2, A, B](implicit
        iterator: JavaIterator.Aux[A, JColl1],
        factory: JavaFactory[B, JColl2],
        aToB: PartialTransformer[A, B]
    ): PartialTransformer[JColl1, JColl2] =
      ???

    implicit def strToInt: PartialTransformer[String, Int] = ???

    //implicitly[PartialTransformer[java.util.ArrayList[String], java.util.BitSet]].toString

    val foo: PartialTransformer[java.util.ArrayList[String], java.util.BitSet] = partialForJavaToJava
  }
}

produces (Scala 2.12)

[error] /Users/dev/Workspaces/GitHub/chimney/chimney-java-collections/src/main/scala/io/scalaland/chimney/javacollections/JavaIterator.scala:32:82: ambiguous implicit values:
[error]  both method iterator in object JavaIterator of type [A]=> io.scalaland.chimney.javacollections.JavaIterator.Aux[A,java.util.Iterator[A]]
[error]  and method bitSet in object JavaIterator of type => io.scalaland.chimney.javacollections.JavaIterator.Aux[Int,java.util.BitSet]
[error]  match expected type io.scalaland.chimney.javacollections.JavaIterator.Aux[A,JColl1]
[error]     val foo: PartialTransformer[java.util.ArrayList[String], java.util.BitSet] = partialForJavaToJava

which is absolutely absurd, as java.util.Iterator and java.util.BitSet have only java.lang.Object as the only common supertype, and none of them is s supertype to java.util.ArrayList, the actually resolved type (which is a subtype of java.util.Iterable).

If we managed to pull this off we could have only 2 implicit for all cases: Iterator, Enumeration, Iterable, Dictionary, Map, Properties, BitSet, etc. handling collections with and without type bounds, iterating over one or two values (maps and map-like).

For now however I am skipping on this effort as a lost a few hours and get nowhere with it.

[MateuszKubuszok]

For now however I am skipping on this effort as a lost a few hours and get nowhere with it.

Actually I managed to fix that! Refactored

[MateuszKubuszok]

Question: shouldn't such structure live in core? Would we reuse it somewhere else? If we want to enure binary compatibility we should decide where to put this utility before releasing it since shoving it around would break binary compatibility.

[MateuszKubuszok]

I think that support for java.util.Enum can be done in a separate PR, as this one is already quite large and macro support is not needed for this PR to work. So java.util.Enum is removed from TODOs and java.lang.Enum support will be developed in #393.

[MateuszKubuszok]

While it wasn't intended for 0.8.0 (more like 0.8.1) I decided to merge it, as it will be useful in convincing people to update.