Add: Support Scala Language

[YuMuuu]

close: #522

This PR adds comprehensive Scala language support to serena.

I have implementation of solidlsp for scala(metals).

required dependency: coursier

[YuMuuu]

parameter reference:

https://scalameta.org/metals/docs/editors/vim#files-and-directories-to-include-in-your-gitignore

[MischaPanch]

Overall looks good, tests for finding references are missing before it can be merged. Thanks for adding Scala support to Serena!

[MischaPanch]

as mentioned above, pls add tests on finding references within the same file and across files

[YuMuuu]

2577779

[MischaPanch]

see comment below

[MischaPanch]

@YuMuuu

umm. i passed tests on local(arm mac)

You probably need to override and increase _get_wait_time_for_cross_file_referencing

[MischaPanch]

I merged main where a fix regarding this was recently pushed and bump the waiting time. Let's see if that worked

[MischaPanch]

I also passes locally for me on ubuntu

[YuMuuu]

I think that not only LSP but also build tool dependencies are necessary.

[MischaPanch]

I think the state in b787b30 was good, maybe just more waiting needed. It did work locally for me without installing any build tools, just after installing coursier

[YuMuuu]

I think the state in b787b30 was good, maybe just more waiting needed. It did work locally for me without installing any build tools, just after installing coursier

Thank you for your confirmation. I will revert the commit!

[YuMuuu]

...

[MischaPanch]

I think a 5 sec wait was enough, it's running through on Ubuntu and macOS. I'll have a look at what's wrong on windows, I suppose either some path issue (using wrong separator), or a fundamental problem in the LS itself

[MischaPanch]

@YuMuuu thanks! I will try running the tests locally by following the guide and if everything works out, we can merge this

[MischaPanch]

@YuMuuu I readded the test files to try the setup you recommend in the docs. I added the plugins.sbt as suggested there.

With the manual setup, sbt -Dbloop.export-jar-classifiers=sources bloopInstall works but sbt compile gives

sbt compile                                               
[info] welcome to sbt 1.10.1 (Eclipse Adoptium Java 21.0.8)
[info] loading settings for project scala-build from metals.sbt,plugins.sbt ...
[info] loading project definition from C:\Users\misch\Projects\oraios\serena\test\resources\repos\scala\project
[info] loading settings for project scala from build.sbt ...
[info] set current project to scala (in build file:/C:/Users/misch/Projects/oraios/serena/test/resources/repos/scala/)
[info] Executing in batch mode. For better performance use sbt's shell
[info] compiling 2 Scala sources to C:\Users\misch\Projects\oraios\serena\test\resources\repos\scala\target\scala-2.13\classes ...
[error] C:\Users\misch\Projects\oraios\serena\test\resources\repos\scala\src\main\scala\Main.scala:13:16: not found: value User
[error]     val user = User("Alice", 30)
[error]                ^                                                                 
[error] C:\Users\misch\Projects\oraios\serena\test\resources\repos\scala\src\main\scala\Main.scala:16:19: not found: value Product
[error]     val product = Product(1, "Laptop", 999.99)
[error]                   ^
[error] C:\Users\misch\Projects\oraios\serena\test\resources\repos\scala\src\main\scala\Main.scala:30:25: not found: type User
[error]   def processUser(user: User): Unit = {
[error]                         ^
[error] three errors found
[error] (Compile / compileIncremental) Compilation failed
[error] Total time: 4 s, completed 01.10.2025, 23:26:3

Is that to be expected? I thought the test files were a valid scala project.

Btw, I have a new laptop with windows and had to install the scala toolchain from scratch. The executables I get are all .bat files and I had to alias all of them to work like alias sbt=sbt.bat in git bash. That is quite annoying - is that how scala users work on Windows? Maybe that should be added to the docs, or am I just misunderstanding something.