Move to Scala 2.13.0-M5

[ashawley]

Previously, #222.

Work from this branch has already been published from the 1.1.0 tag in #256.

• Serialization problem, Serialization in 2.13.0-M5 #254, affects only 2.13 builds
• Scala.js 1.0.0-M5 not having a 2.13.0-M5 build

[SethTisue]

I think you'd need to rebase this one to see the reduced diffs

[SethTisue]

Sébastien says Scala.js 1.0.0-M5 won't (can't) be published for Scala 2.13.0-M5, so I'd suggest simply excluding that combination from the matrix.

[ashawley]

One thing that came up in the original collections rewrite changes for 2.13.0-M4 in #222 were the new version-specific traits. We made these traits private. This access modifier means people can't use it as a trait. However, the traits are published, and they are revealed in the type signatures.

 :type -v <x y="z"/>.attributes
// Type signature
scala.xml.MetaData

// Internal Type structure
TypeRef(
  TypeSymbol(
    abstract class MetaData extends AbstractIterable[scala.xml.MetaData] 
                   with Iterable[scala.xml.MetaData] 
                   with Equality 
                   with ScalaVersionSpecificIterableSerializable[scala.xml.MetaData] 
                   with Serializable

  )
)

Fortunately (or unfortunately), dropping such a trait from a future version will be caught by Mima:

> xml/mimaReportBinaryIssues
[info] scala-xml: found 13 potential binary incompatibilities while checking 
[info] against org.scala-lang.modules:scala-xml_2.13.0-M5:1.1.1
...
[error]  * the type hierarchy of class scala.xml.NodeSeq is different in 
[error]  current version. Missing types {scala.xml.ScalaVersionSpecificIterableSerializable}
[error]    filter with: ProblemFilters.exclude[MissingTypesProblem]("scala.xml.NodeSeq")

Cost of doing business or should we do something else? These weren't released in any of the 2.11 and 2.12 builds, yet, so I feel it's not too late to change course.

[SethTisue]

Cost of doing business or should we do something else?

gah, it's not too horrible, but yuck anyway. do you have an alternative in mind?

agree it's certainly not too late to change course.

[SethTisue]

just MiMa complaining, now

[ashawley]

gah, it's not too horrible, but yuck anyway. do you have an alternative in mind?

Well, I suppose we could source the entire files in the version-specific directories. That would be the alternative, but it's not ideal.

[SethTisue]

yay!