Allow treating every Scala CLI script as separate project.

[kasiaMarek]

Is your feature request related to a problem? Please describe.

Scala CLI scripts are often used a single file entities and people might have multiple of such scripts in a single directory for different tasks. Currently metals will treat all this scripts as single project, which is not always desired.

original issue: VirtusLab/scala-cli#3367

Describe the solution you'd like

Create a special script mode in Metals where each file would be considered as a separate project.

The solution could reuse FallbackMetalsLspService which is currently used for single file support. It starts a Scala CLI server for each file keeping a pool to up to 10 servers (this number could be configurable).

Alternatively

Metals should by default treat each script as a separate project. Plus add a setting that will disable this and .sc will be treated as part of the project (as currently).

Describe alternatives you've considered

• Opening each script as a single file in the editor.
• Keeping each script in a separate folder and opening them as workspace folders.
• Adjusting definitions and imports in the script so they don't have conflicts and can be treated as single build.

Additional context

Starting a new server for each file isn't perfect but Scala CLI server are quite lightweight, since they mostly proxy things to Bloop. Other solution would require multi-module builds in Scala CLI, which is out of its designed scope.

Search terms

scala-cli, scripts

[SethTisue]

Nice to see this is being considered. "Folder full of scripts" is actually my main use case for scala-cli.

[dragove]

File dependency should also be considered.
For example, I have file util.sc as following

//> using scala 3.6.3
//> using dep com.lihaoyi::os-lib:0.11.3
def writeHello() = os.write(os.pwd / "x.txt", "hi\n")

and main.sc as following

//> using file util.sc
import util.writeHello
writeHello()

Currently run scala-cli main.sc generates warning:

[warn]  Using directives detected in multiple files:
- main.sc:1:1-23
- util.sc:1:1-2:41
It is recommended to keep them centralized in the /home/dove/Workspace/Scala/demo/project.scala file.

from the documentation, there is another problem: Custom source does not support chaining. sources are added only once, not recursively. This is supported by ammonite. It can be useful for managing scripts.