ess: Fix local vars

- Labelled `ess-backend` as safe local variable.
- Added local variable hooks of ess modes:
  - `spacemacs//ess-may-setup-r-lsp`

See: syl20bnr#14653

layers/+lang/ess/config.el

@@ -27,6 +27,7 @@
 
 (defvar ess-r-backend (if (configuration-layer/layer-used-p 'lsp) 'lsp 'ess)
   "The backend to use for IDE features. Possible values are `ess' and `lsp'.")
+(put 'ess-r-backend 'safe-local-variable #'symbolp)
 
 (defvar ess-assign-key nil
   "Call `ess-insert-assign'.")

layers/+lang/ess/packages.el

@@ -79,6 +79,8 @@
            ("\\.[Jj][Oo][Gg]\\'" . ess-jags-mode)
            ("\\.[Jj][Mm][Dd]\\'" . ess-jags-mode))
     :commands (R stata julia SAS ess-julia-mode)
+    :hook (ess-r-mode-local-vars . spacemacs//ess-may-setup-r-lsp)
+          (inferior-ess-mode . spacemacs//ess-fix-read-only-inferior-ess-mode)
     :init
     (progn
       (setq ess-use-company nil
@@ -91,10 +93,6 @@
 
       (spacemacs/register-repl 'ess-site #'spacemacs/ess-start-repl)
 
-      (add-hook 'ess-r-mode-hook #'spacemacs//ess-may-setup-r-lsp)
-      (add-hook 'inferior-ess-mode-hook
-                'spacemacs//ess-fix-read-only-inferior-ess-mode)
-
       (with-eval-after-load 'ess-julia
         (spacemacs/ess-bind-keys-for-julia))
       (with-eval-after-load 'ess-r-mode