"edit.sortMembers is already registered" when switching SDKs with LSP

[DanTup]

When using LSP, sometimes switching SDKs will result in a failure to initialize the language server ("edit.srtMembers is already registered").

I thought it may be related to microsoft/vscode-languageserver-node#723 but now I'm not so sure. Could be a race between shutting down the old server and starting the new one, but you'd expect starting up to be way slower than the shutdown.

[DanTup]

New theory is that this only occurs if you trigger two servers to overlap - by changing SDK again while the other is still starting up. We can prevent this by not allowing the SDK switcher to work until the analysis server is ready.

[DanTup]

New theory:

1. Server starts
2. (time passes)
3. Initialization response includes command names
4. LSP client registers commands
5. ...
6. Server is shutdown
7. Calls dispose, which unregisters commands

The issue is if the server is shutdown during (2), it calls dispose immediately (unregistering nothing) and then the initialisation step still registers the commands (which are never removed).

[DanTup]

Filed microsoft/vscode-languageserver-node#725.

[DanTup]

Fixed with new LSP client.