Change MiMa config in scala/scala to check against older versions too?

[SethTisue]

In scala/scala's project/MimaFilters.scala we currently have:

project/MimaFilters.scala:    mimaReferenceVersion := Some("2.13.9"),
project/MimaFilters.scala:    mimaPreviousArtifacts       := mimaReferenceVersion.value.map(organization.value % name.value % _).toSet,

Are we sure that we don't also need to check against 2.13.0, or against all previous 2.13.x versions? (And same on 2.12.x branch?)

I've opened lightbend-labs/mima#724 as a discussion on this for library maintainers generally, but I'm also opening this separate ticket, since the situation in scala/scala is a bit different than most libraries, since scala-library is checked for both forwards and backwards bincompat. Many library maintainers only maintain backwards bincompat.

[SethTisue]

Removing my assignment, as perhaps the status quo on this is just fine, actually.

Anyway,

scala-library is checked for both forwards and backwards bincompat.

This is no longer the case after SIP-51 — we are now backwards-only.

[armanbilge]

Are we sure that we don't also need to check against 2.13.0, or against all previous 2.13.x versions?

To be safe, you do. To be more specific, you definitely need to if you use the package-private trick, or, we need to change how MiMa works to restore the transitive property for backwards-compatibility-checking. See thread in lightbend-labs/mima#724 (reply in thread).