Support for https://pyrefly.org/ ?

[oscarvarto]

Is your feature related or already mentioned on the wishlist?

No

Describe your feature here.

Add pyrefly support for Python development on Emacs. It seems to be fast.
Documentation mentions support for some other tooling: https://pyrefly.org/en/docs/IDE/#other-editors
There is also a "simple" extension for Zed (https://github.com/zed-extensions/pyrefly)

[elge70]

;;----------------------------------------------------------------------------
;;Just cut and pasted the ty code and it is working
;;----------------------------------------------------------------------------

;;; Commentary:

;; LSP Clients for the Python(pyrefly) Type Checker .

;;; Code:

(require 'lsp-mode)

(defgroup lsp-python-refly nil
  "LSP support for Python(pyrefly)."
  :group 'lsp-mode
  :link '(url-link "https://pyrefly.org"))

(defcustom lsp-python-refly-clients-server-command '("pyrefly" "lsp")
  "Command to start the python pyrefly language server."
  :group 'lsp-python-refly
  :risky t
  :type '(repeat string))

(lsp-register-client
 (make-lsp-client :new-connection (lsp-stdio-connection (lambda () lsp-python-refly-clients-server-command))
                  :activation-fn (lsp-activate-on "python")
                  :priority -1
                  :add-on? t
                  :server-id 'py-refly))

(lsp-consistency-check lsp-python-refly)

(provide 'lsp-python-refly)

[gpanago]

I also had success with a similar snippet:

(setq lsp-pyrefly-extra-paths '("..."))
(lsp-register-client
   (make-lsp-client :new-connection (lsp-stdio-connection (lambda () '("pyrefly" "lsp" "-j" "19")))
                    :activation-fn (lsp-activate-on "python")
                    :priority 3
                    :multi-root 't
                    :environment-fn (lambda() '(("PYTHONPATH" . lsp-pyrefly-extra-paths)))
                    :server-id 'pyrefly-ls))

Note: I think it would be useful to have a multi-root option (as pyrefly supports it and ty doesn't) and an extra paths option, although I don't think that PYTHONPATH is the right way.

Still, I am getting a few weird errors on stderr:

Handling non-canceled request textDocument/documentHighlight (34930)
Handling non-canceled request textDocument/hover (34931)
Handling non-canceled request textDocument/completion (34939)
We should cancel request RequestId(I32(34939))
We should cancel request RequestId(I32(34940))
We should cancel request RequestId(I32(34941))
Request 34940 is canceled
Request 34941 is canceled
Handling non-canceled request textDocument/completion (34945)
Handling non-canceled request textDocument/documentHighlight (34953)
Handling non-canceled request textDocument/hover (34954)

and a lot more similar errors.

[oscarvarto]

@elge70 Thanks a lot!
It seems your solution works for me.