What's lsp-deferred?

[gzagatti]

LSP is working fine with my configuration, but as I'm trying to tweak the configuration to suit my needs I came across the command lsp-deferred in the installation page. It says:

To defer LSP server startup (and DidOpen notifications) until the buffer is visible you can use lsp-deferred instead of lsp:

(add-hook 'XXX-mode-hook #'lsp-deferred)

What do you mean by defer the server startup until the buffer is visible? What happens when it is not deferred?

[kiennq]

What do you mean by defer the server startup until the buffer is visible? What happens when it is not deferred?

If it's not deferred, the server starts immediately when the lsp command is encountered.
That can take a very long time when you open several buffers at one and have lsp-mode starts in all of them. You can even feel like Emacs is hanging.

An example is when you restore from desktop-save-mode and have a dozen buffers restored, you may not want to have lsp-mode running in all of the buffers immediately, but only when they're visible in your view.

[gzagatti]

Thanks so much for the detailed response.