Follow-up on Zinc upgrade

[adpi2]

The purpose of this issue is to track the progress on the upgrade of Zinc that follows #10607.

The current situation is:

• scala3-compiler depends on "org.scala-sbt" % "compiler-interface" % "1.3.5" and use the deprecated API
• scala3-sbt-bridge depends on "org.scala-sbt" % "compiler-interface" % "1.4.3" and contains 2 implementations: the old xsbt.CompilerInterface that is used by sbt 1.3.x and Mill, and the new dotty.tools.xsbt.CompilerBridge that is used by sbt 1.4.x.

The plan is to bump the version of Zinc in scala3-compiler and use the new API but first we need Mill and Bloop to upgrade to Zinc 1.4.3.

• Bump the version of Zinc in Mill to 1.4.3 and use the new API
• Bump the version of Mill in the community build
• Bump the version of Zinc in Bloop
• Bump the version of Zinc in scala3-compiler and use the new API (waiting on use new zinc 1.8 api for VirtualFile #18137)
• Remove the old xsbt.CompilerInterface

At the end, the scala3-compiler won't be compatible any more with sbt 1.3.x, Mill 0.9.x and Bloop 1.4.x

[adpi2]

Mill 0.9.4-15-79937c is now using Zinc 1.4.4.

[adpi2]

Bloop migration to Zinc 1.4.x is in progress here: scalacenter/bloop#1477

[TheElectronWill]

Bloop has migrated to Zinc 1.6 earlier this year: scalacenter/bloop#1662 🎉

[ckipp01]

Btw @bishabosha will this also be closed by the work you've been doing with the zinc upgrade?

[bishabosha]

At least point 4 is done, not sure if we should remove the old zinc api - it would enforce a higher minimum sbt version

[adpi2]

At least point 4 is done, not sure if we should remove the old zinc api - it would enforce a higher minimum sbt version

If I remember correctly the new API in scala3-compiler is incompatible with the old interface in the bridge. It would fail to compile incrementally on the old sbt versions. So we can and should remove the old xsbt.CompilerInterface.

[armanbilge]

Another motivation for this issue: compiler-interface 1.3.5 depends on an old, vulnerable version of Google Protobuf. This is being flagged up in several projects using the new sbt-dependency-submission action.

[adpi2]

The upgrade of Zinc in the compiler is almost there: #18137