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VirtusLab / scala-cli

Scala CLI is a command-line tool to interact with the Scala language. It lets you compile, run, test, and package your Scala code (and more!)
https://scala-cli.virtuslab.org
Apache License 2.0
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Directive for specifying minimum JVM version #3205

Open marcinzh opened 2 months ago

marcinzh commented 2 months ago

Is your feature request related to a problem? Please describe. I have a library that is compiled for Java 11. When running Scala-cli scripts, I need the JVM version to be at least 11, but the current directive //> using jvm 11 causes Java 11 to be downloaded and used, even if the system already has a newer JVM version (e.g., Java 21) installed. This is undesirable, as I would prefer to use the newer JVM when available.

Describe the solution you'd like I would like to be able to specify a minimum JVM version for my script. This would allow the script to run on any JVM that meets or exceeds the required version without forcing the download of an older JVM.

Proposed syntax:

//> using jvm 11+

Or:

//> using jvm >= 11

Describe alternatives you've considered

  1. Using the existing directive //> using jvm 11 . However, this causes Java 11 to be downloaded, even when a newer version is already installed.

  2. Not using any directive at all. This approach results in an error when the script is executed, as the JVM may not meet the minimum version requirements and produces cryptic errors about class file versions. To diagnose the error, the user is forced to make a research about which JVM version corresponds to which class file version (e.g. Java 11 <-> class file format v55).

Additional context This feature would make it easier to work with projects requiring specific Java versions, without unnecessary downloads of older JVM versions when a suitable newer version is already installed.

Gedochao commented 2 months ago

Seems like we'd go with this syntax:

//> using jvm 11+

Note that we would not support this when a particular JVM distro is chosen, so:

//> using temurin:11+
// this is invalid

We'd support this via the CLI option --jvm as well.