Documentation on LanguageClient lifecycle

[nrc]

I've been looking for documentation on LanguageClient, but can't find any either in the source or online (there's lots of information on the language server, but not so much about using LanguageClient in the extension. In particular I'm looking for documentation on when/if I should be calling stop or other lifecycle functions.

My motivation here is to properly handle the language server restarting. I run the extension which starts the language server (the Rust Language Server). If I then kill the language server process, then the language server is restarted. However, I'm not clear what happens to the language client or the extension itself - I don't know if there hooks where I'm meant to handle stopping the client.

What happens is that the new language server gets two of every message, so it seems like there are now two clients sending messages to the same server (and if I keep killing the language server, I get n+1 messages after n restarts). I assume this is because I'm not handling something in the extension, but it could be a bug in VSCode itself.

[vscodebot]

(Experimental duplicate detection)
Thanks for submitting this issue. Please also check if it is already covered by an existing one, like:

• The Java Language Server server crashed 5 times in the last 3 minutes (#47936)
• Document guidelines to enable language features for embedded languages (#47288)
• VSCode Remote Client and Headless Server [feature request] (#35671)

[dbaeumer]

@nrc agree that there is not a lot of documentation for the client itself except the source code and some examples here: https://github.com/Microsoft/vscode-extension-samples

Regarding your questions: you need to call stop in the deactivate method of your extension to stop the client which stops the server. When a server crashes the client restarts the server. It will not create a new instance of the server. You can control this behavior using the LanguageClientOptions#errorHandler property. If you see problems with server restarts please file a GitHub issue here: https://github.com/Microsoft/vscode-languageserver-node

[nrc]

Thanks @dbaeumer, it sounds like there are not lifecycle things that I am missing and that there might be a bug in the client. I filed microsoft/vscode-languageserver-node#342