I have configured lsp-mode as follows:
(use-package lsp-mode
:straight t
:init (setq lsp-keymap-prefix "C-c l")
:hook ((python-mode . lsp))
:commands lsp)
I am also using desktop-save-mode to restore my editing state upon restart. When I have several projects open and quit Emacs, the restart takes a long time as it starts each lsp server. Is there a way to start each server only when I run an lsp-related command in the buffer?
How about:
(use-package lsp-mode
:straight t
:init (setq lsp-keymap-prefix "C-c l")
:hook (python-mode . lsp-deferred))
The doc for lsp-deferred:
Signature
(lsp-deferred)
Documentation
Entry point that defers server startup until buffer is visible.
lsp-deferred will wait until the buffer is visible before invoking lsp.
This avoids overloading the server with many files when starting Emacs.
Edit: I've encountered some issues with this as described by scry, if the above doesn't work, try his workaround (I've opened a PR here: https://github.com/emacs-lsp/lsp-mode/pull/3975).
The accepted answer didn't work for me, since when lsp-mode is already listed as a minor mode in the saved buffers, desktop-read will activate it before lsp-deferred runs.
Instead, I'm using this:
(defun my-lsp-deferred-on (_)
(lsp-deferred))
(setq desktop-minor-mode-table
'((lsp-mode my-lsp-deferred)
...))
desktop-minor-mode-table tells Desktop how to restore the minor mode:
Table mapping minor mode variables to minor mode functions.
Each entry has the form (NAME RESTORE-FUNCTION).
NAME is the name of the buffer-local variable indicating that the minor
mode is active. RESTORE-FUNCTION is the function to activate the minor mode.
Note that the function is called with one argument like a minor-mode function, but lsp-deferred takes none, hence the placeholder; also, it has to be mapped by its name, so we can't just use a lambda.
