Trying to subclass eglot-lsp-server

[benbellick]

Hi! I actually had been trying to implement #1420 myself by doing what the documentation had suggested, which is to alter the eglot-server-programs so that the value for c++-mode goes from this:

                                ((c-mode c-ts-mode c++-mode c++-ts-mode objc-mode)
                                 . ,(eglot-alternatives
                                     '("clangd" "ccls")))

to this:

                                ((c-mode c-ts-mode c++-mode c++-ts-mode objc-mode)
                                 . ('eglot-lsp-server . ("clangd"))))

Then, I would later replace 'eglot-lsp-server with my own custom subclass. This was informed by the documentation string for the variable which says contact can be (emphasis mine)

A cons (CLASS-NAME . INITARGS) where CLASS-NAME is a symbol
designating a subclass of eglot-lsp-server, for representing
experimental LSP servers. INITARGS is a keyword-value plist
used to initialize the object of CLASS-NAME, or a plain list
interpreted as the previous descriptions of CONTACT. In the
latter case that plain list is used to produce a plist with a
suitable :PROCESS initarg to CLASS-NAME. The class
eglot-lsp-server descends from jsonrpc-process-connection,
which you should see for the semantics of the mandatory
:PROCESS argument.

However I get the error

Wrong type argument: processp, nil

Any suggestions on what I am doing wrong here? Am I misunderstanding the docs? Anyways, thanks! this package rocks

[joaotavora]

This would seem to be a bug. Either in the doc or in the implementation. I have to check.

[joaotavora]

This would seem to be a bug. Either in the doc or in the implementation. I have to check.

Never mind, no it isn't.

[joaotavora]

Any suggestions on what I am doing wrong here?

You have to brush up on your Lisp quoting rules (and I must play closer attention):

(setq-local eglot-server-programs
     '((c-mode c-ts-mode c++-mode c++-ts-mode objc-mode)
                                 . (eglot-lsp-server . ("clangd"))))

Is how it should be. This of course is the same as

(setq-local eglot-server-programs
     '((c-mode c-ts-mode c++-mode c++-ts-mode objc-mode)  eglot-lsp-server "clangd"))

But what you had was wrong (for Eglot's purposes) because ' means the same as applying the form quote. So this:

(setq-local eglot-server-programs
     '((c-mode c-ts-mode c++-mode c++-ts-mode objc-mode)
                                 . ('eglot-lsp-server . ("clangd"))))

is the same as this (I think):

(setq-local eglot-server-programs
     (quote ((c-mode c-ts-mode c++-mode c++-ts-mode objc-mode)
                                 . ((quote eglot-lsp-server) . ("clangd")))))

Which is wrong: has too much quoting.

[benbellick]

Nice catch, thank you!!