Scala 3.5 is using the wrong launcher

[JD557]

Scala 3.5.0 is using the default dotty.tools.MainGenericRunner: https://github.com/coursier/apps/blob/main/apps/resources/scala.json#L2

In turn, the following warning is launched:

[warning] MainGenericRunner class is deprecated since Scala 3.5.0, and Scala CLI features will not work.
[warning] Please be sure to update to the Scala CLI launcher to use the new features.
[warning] It appears that your Coursier-based Scala installation is misconfigured.
[warning] To update to the new Scala CLI runner, please update (coursier, cs) commands first before re-installing scala.
[warning] Check the Scala 3.5.0 release notes to troubleshoot your installation.

So I think we need to define a mainClass override, similar to https://github.com/coursier/apps/blob/main/apps/resources/scala.json#L35

But I don't know what's the new main class 😓

[SethTisue]

@bishabosha I think either this might interest you, or you could suggest who else might want to take a look?

[bishabosha]

You need to reinstall coursier, or at least try to update it first, then reinstall scala - there should probably be a note added to the blog post

e.g. if you read the error message, it tells you what to do

[warning] To update to the new Scala CLI runner, please update (coursier, cs) commands first before re-installing scala.
[warning] Check the Scala 3.5.0 release notes to troubleshoot your installation.

@JD557 did you follow the steps before opening the issue? - perhaps the message is incorrect

[bjornregnell]

Well well. Still only a few early adopters have already installed. (But I'm counting the hours until my 200+ students will go ahead and install on all sorts of boxes...)

[lego-eden]

For some reason running cs install scala:3.5.0 fixes this error message.

[bishabosha]

@bjornregnell hopefully this shouldn't affect users who install coursier for the first time

Edit: it seems it is incorrect - version overrides only kick in apparently for explicit versions

[bjornregnell]

@JD557 did you follow the steps before opening the issue?

I have followed all the steps and it only works if you give an explicit cs install scala:3.5.0 after a clean install (as pointed out by @lego-eden) , which is not apparent from the install instructions...

See further here: https://contributors.scala-lang.org/t/3-5-0-release-thread/6666/66

[bjornregnell]

@bishabosha how fast can a new cs version be released if needed? or an updated JSON if that is enough?

[bishabosha]

I have followed all the steps and it only works if you give an explicit cs install scala:3.5.0 after a clean install

ok I can reproduce that, perhaps we can rewrite the scala.json to make the native runner the default, and then version overrides use jvm launcher?

[bjornregnell]

that would be great! Do you know what the JSON should say instead?

[Gedochao]

@JD557 To clarify, it definitely isn't about the main class, so might be worth it to update the issue name, to avoid confusion.
For Scala 3.5.0+ it should use a native binary for the runner rather than the old scala runner JAR.
This is already happening for explicit cs install scala:3.5.0 with coursier v2.1.10, but it seems it is not when a simple update is called instead.
We'll likely need to look for a fix and release a new coursier launcher... 😕

[JD557]

Ok, I edited the title to a more generic one

[bishabosha]

@Gedochao please check out my PR #239 - no need to release a new launcher - just the channel descriptor