lsp-defcustom not compatible with setting local variables

[brownts]

Thank you for the bug report

• I am using the latest version of lsp-mode related packages.
• I checked FAQ and Troubleshooting sections
• You may also try reproduce the issue using clean environment using the following command: M-x lsp-start-plain

Bug description

LSP servers which need to be configured by a directory local variable (e.g., project file for Ada LS), aren't initialized correctly when that configuration is set using a normal directory local variable. This happens even when delaying the initialization of lsp to the hack-local-variables-hook as specified in the FAQ. The reason for this is that lsp-defcustom utilizes a custom set function which invokes lsp-register-custom-settings, and this setter is not invoked using the hack-local-variables initialization, which just creates a buffer local variable (via make-local-variable).

I've been able to work around this by using eval and setopt in my .dir-locals.el to cause the setter to be invoked, like this:

;;; Directory Local Variables            -*- no-byte-compile: t -*-
;;; For more information see (info "(emacs) Directory Variables")

((ada-ts-mode . ((eval . (setopt lsp-ada-project-file "src/gtkada.gpr")))))

However, I think it might be better for lsp-mode to look through the buffer local variables when it starts up and call the setter for any of them which correlate to an lsp-defcustom. That would allow the normal setting of directory local variables to work without resorting to eval and setopt as demonstrated above.

Steps to reproduce

Setting a directory local variable in the normal way for a lsp-defcustom (i.e., lsp-ada-project-file) should cause the issue to be observed. Using this approach, the lsp-defcustom's default value (e.g., "default.gpr") is used when first connecting with the server.

Expected behavior

I expect the value specified in the directory-local variable to be used when communicating with the server.

Which Language Server did you use?

Ada Language Server

OS

Linux

Error callstack

No response

Anything else?

No response