feat(emacs): Basic LSP

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

users/crumb/programs/emacs/modules/lang/syd-lang-nix.el

@@ -0,0 +1,8 @@
+;;; syd-lang-nix.el -*- lexical-binding: t; -*-
+
+(use-package nix-mode
+  :mode "\\.nix\\'"
+  :config
+  (add-hook 'nix-mode-hook #'lsp))
+
+(provide 'syd-lang-nix)

users/crumb/programs/emacs/modules/syd-lang.el

@@ -2,5 +2,6 @@
              (file-name-concat user-emacs-directory "modules" "lang"))
 
 (require 'syd-lang-emacs-lisp)
+(require 'syd-lang-nix)
 
 (provide 'syd-lang)

users/crumb/programs/emacs/modules/syd-tooling.el

@@ -0,0 +1,30 @@
+;;; syd-tooling.el -*- lexical-binding: t; -*-
+
+(use-package lsp-mode
+  :init
+  ;; We'll bind things ourselves.
+  (setq lsp-keymap-prefix nil)
+  ;; Keep state out of my config dir.
+  (setq lsp-session-file (file-name-concat syd-data-dir "lsp-session")
+        ;; We disable `lsp-install-server', but I don't want this to be nil.
+        lsp-server-install-dir (file-name-concat syd-data-dir "lsp"))
+  ;; Disable features that have great potential to be slow.  LSPs tend to be
+  ;; quite slow compared to non-LSP equivalents.
+  (setq lsp-enable-folding nil
+        lsp-enable-text-document-color nil)
+  ;; Reduce unexpected modifications to code
+  (setq lsp-enable-on-type-formatting nil)
+  ;; Make breadcrumbs opt-in; they're redundant with the modeline and imenu
+  (setq lsp-headerline-breadcrumb-enable nil)
+  :hook (lsp-mode . lsp-enable-which-key-integration)
+  :commands lsp
+  :config
+  (syd-defadvice syd-lsp-install-server-a ()
+    "Override and disbale `lsp-install-server'"
+    :override #'lsp-install-server
+    (user-error (concat "Ignoring a call to `lsp-install-server'"
+                        " — tell the caller to use Nix!")))
+  (set-popup-rule! (rx line-start "*lsp-" (or "help" "install"))
+    :size 0.35 :quit t :select nil))
+
+(provide 'syd-tooling)