Ensure vague Scala versions are capped at defaults

[Gedochao]

Fixes #3233

Note: this may potentially be a breaking change.

This changes how Scala version is picked whenmajor or major.minor prefixes are passed, rather than the full version tag:

• -S 3 will now point to the launcher default Scala 3 Next version, rather than whatever is the latest stable that coursier can find upstream
• similarly, -S 3.<current launcher default minor> will now point to the launcher default Scala 3 Next version
• -S 2.13 will point to the launcher default Scala 2.13 version (which up till now only affected tests and generated docs)
• similarly, -S 2.12 will now point to the launcher default Scala 2.12 version
• launcher defaults are overridden for a particular Scala series with the --cli-user-scala-version to accomodate for Scala CLI installed as scala

Or, to give examples, with what is currently on sonatype:

• -S 3
  • before

  scala-cli -with-compiler -e 'println(dotty.tools.dotc.config.Properties.versionNumberString)' -S 3
  # Compiling project (Scala 3.6.1, JVM (17))
  # Compiled project (Scala 3.6.1, JVM (17))
  # 3.6.1

  • after

  scala-cli -with-compiler -e 'println(dotty.tools.dotc.config.Properties.versionNumberString)' -S 3
  # Compiling project (Scala 3.5.2, JVM (17))
  # Compiled project (Scala 3.5.2, JVM (17))
  # 3.5.2

• -S 3, when --cli-user-scala-version 3.6.0
  • before

  scala-cli --cli-user-scala-version 3.6.0 -with-compiler -e 'println(dotty.tools.dotc.config.Properties.versionNumberString)' -S 3
  # Compiling project (Scala 3.6.1, JVM (17))
  # Compiled project (Scala 3.6.1, JVM (17))
  # 3.6.1

  • after

  scala-cli --cli-user-scala-version 3.6.0 -with-compiler -e 'println(dotty.tools.dotc.config.Properties.versionNumberString)' -S 3
  # Compiling project (Scala 3.6.0, JVM (17))
  # Compiled project (Scala 3.6.0, JVM (17))
  # 3.6.0

• -S 3.5
  • before

  scala-cli --cli-user-scala-version 3.5.1 -with-compiler -e 'println(dotty.tools.dotc.config.Properties.versionNumberString)' -S 3.5 
  # Compiling project (Scala 3.5.2, JVM (17))
  # Compiled project (Scala 3.5.2, JVM (17))
  # 3.5.2

  • after

  scala-cli --cli-user-scala-version 3.5.1 -with-compiler -e 'println(dotty.tools.dotc.config.Properties.versionNumberString)' -S 3.5 
  # Compiling project (Scala 3.5.1, JVM (17))
  # Compiled project (Scala 3.5.1, JVM (17))
  # 3.5.1

For more examples, refer to the test suite cases.

The purpose of this change is to safeguard against future incidents similar to the Scala 3.6.0 mis-release. When a new Scala version is released on sonatype, Scala CLI will no longer pick it up automatically with vague version tags (such as -S 3). Of course, any version remains usable when the entire version string is passed (so -S 3.6.1 remains valid for any launcher).

The downside of this change is that the meaning of a vague version string will change on scala-cli launcher upgrade.

[tgodzik]

I wonder should the other option be to check if https://github.com/scala/scala3/releases/tag/${scalaVersion} exists?

[Gedochao]

I wonder should the other option be to check if https://github.com/scala/scala3/releases/tag/${scalaVersion} exists?

It does exist for 3.6.1, though...

[SethTisue]

👏