`stopLanguageServer()` hangs, preventing Stop/Restart from working correctly

[xeger]

Whenever I use the "Syntax Tree: Stop" command on my system, the await languageClient.stop() never returns. I've verified that the ruby process disappears from ps output, so it there's sort of unclean shutdown happening in the language server client (provided by VS Code).

After debugging, I isolated the root cause: the VS Code client expects a response to every RPC, including shutdown. The syntax_tree gem was abruptly terminating on shutdown requests without providing a response.

I have a proposed fix in the gem that responds to shutdown requests & verified this makes VS Code happy.

This fix reveals another issue: because Visualize registers a command every time it is constructed, VS Code throws an error if the language server is started a second time! It might be a bug for us to (re)register the command inside startLanguageServer -- we need a proxy command function that will forward to the most recently constructed instance of Visualize.

My goal is to be able to cleanly restart the language server -- because I want to add settings to the extension and ensure the LSP restarts when settings are tweaked; see #3. Seems like fixing the LSP in the gem is the first step to that, although I need to fix the command-reregistration issue too, if I'm going to make settings work.

Thoughts?

[kddnewton]

In terms of fixing the visualize issue, I think it should boil down to:

• Have the activate function register the command instead
• Have it do nothing if the languageClient variable is null
• Otherwise have it call the visualize instance's visualize function