Try to launch ENSIME server

[laughedelic]

See #1 (comment).

• Related issue: Running outside of vscode dragos/dragos-vscode-scala#72
• Relevant code: https://github.com/dragos/dragos-vscode-scala/blob/41939453d8efa2ee020bc37236d04fc2b4f7d553/scala/src/extension.ts#L52-L66

[laughedelic]

This launches the ENSIME server, but I don't see anything working in the editor. It loads the processor, I see requests sent and log messages, but don't get any responses.. ☹️

[laughedelic]

I switched to the official ENSIME LSP server, it got recently merged in the 3.0 branch of the ensime-server: https://github.com/ensime/ensime-server/pull/1888 and is a replacement for the dragos' server implementation.

Here's what I got so far:

• the server launches well with coursier
• but it doesn't shutdown properly and you need to kill the process (see here). It leads to several problems:
  • newly launched server may fail on trying to access locked cache
  • even when you kill the zombie, new server may fail to launch (details on demand)
• if it launches well and is running, these things work:
  • textDocument/documentSymbol shows some symbols, but the hierarchy is broken
  • textDocument/definition works quite well and even jumps to the stuff from the project deps
  • textDocument/hover works, but has some glitches (like empty tooltips of showing nonsense when hovering on comments)
  • textDocument/completion seems to work ✨ but breaks once the code doesn't compile and doesn't restore if you fix it
    all of them have problems that have to be fixed in the server, but it's not critical now
• presentation compiler throws lots of false positives and things like Presentation compiler crashed while type checking this file, but this is probably due to that I didn't set the classpath properly..

[laughedelic]

I'm going to merge this as a first step towards ENSIME server support. ENSIME LSP is in improvement process: https://github.com/ensime/ensime-server/pull/1894.

Next step will be #13.