feat(emacs): Basic LSP

Includes basic Nix-mode config for the sake of testing the LSP.

users/crumb/programs/emacs/lib/syd-prelude.el

@@ -4,6 +4,10 @@
 
 (require 'syd-constants)
 
+(use-package dash)
+
+(require 'dash)
+
 (cl-defmacro syd-define-stub
     (name &key (desc "implement me!") interactive)
   (let ((todo (format "%s: TODO: %s" name desc)))
@@ -130,4 +134,35 @@ form."
            (prog1 (progn ,@body)
              (message ""))))))
 
+(defun syd--parse-defadvice-args (arg-list)
+  "Parses the docstring and keywords provided to `syd-defadvice'."
+  (let (docstring
+        advice)
+    (when (stringp (car-safe arg-list))
+      (setq docstring (pop arg-list)))
+    (while (and (length> arg-list 2)
+                (keywordp (car arg-list)))
+      (let ((how (pop arg-list))
+            (sym (pop arg-list)))
+        (push (cons how sym) advice)))
+    ;; What's left of `arg-list' is the body of the defun.
+    (list docstring advice arg-list)))
+
+(defmacro syd-defadvice (name params &rest args)
+  "Define a function and add it as advice."
+  (declare (indent defun))
+  (-let (((docstring advice body) (syd--parse-defadvice-args args)))
+    `(progn (defun ,name ,params
+              ,@(-some-> docstring list)
+              ,@body)
+            ,@(-map (lambda (arg)
+                      (-let (((how . sym) arg))
+                        `(advice-add ,sym ,how #',name)))
+                    advice))))
+
+(syd-defadvice syd-lsp-install-server-a ()
+  :override #'lsp-install-server
+  (user-error (concat "Ignoring a call to `lsp-install-server'"
+                      " — tell the caller to use Nix!")))
+
 (provide 'syd-prelude)