Add LSP support for ESS R

docs/modules.org

@@ -106,7 +106,7 @@ Modules that bring support for a language or group of languages to Emacs.
 + elm - TODO
 + emacs-lisp - TODO
 + erlang - TODO
-+ [[file:../modules/lang/ess/README.org][ess]] - TODO
++ [[file:../modules/lang/ess/README.org][ess]] =+lsp= - TODO
 + [[file:../modules/lang/faust/README.org][faust]] - TODO
 + [[file:../modules/lang/fsharp/README.org][fsharp]] - TODO
 + [[file:../modules/lang/go/README.org][go]] =+lsp= - TODO

modules/lang/ess/README.org

@@ -4,8 +4,15 @@ This module adds support for various statistics languages, including R, S-Plus,
 SAS, Julia and Stata.
 
 * Table of Contents :TOC:
-- [[Appendix][Appendix]]
-  - [[Keybindings][Keybindings]]
+- [[#prequisites][Prequisites]]
+- [[#appendix][Appendix]]
+  - [[#keybindings][Keybindings]]
+
+* Prequisites
+This module has sevral optional dependencies:
+
++ [[https://github.com/jimhester/lintr][lintr]]: Enables R linting.
++ [[https://github.com/REditorSupport/languageserver][languageserver]]: Enables LSP support in an R buffer (with =+lsp= flag).
  
 * Appendix
 ** Keybindings

modules/lang/ess/config.el

@@ -19,9 +19,15 @@
         ess-style 'DEFAULT
         ess-history-directory (expand-file-name "ess-history/" doom-cache-dir))
 
+  (set-docsets! 'ess-r-mode "R")
+  (if (featurep! +lsp)
+      (add-hook 'ess-r-mode-hook #'lsp!)
+    (set-lookup-handlers! 'ess-r-mode
+      :documentation #'ess-display-help-on-object))
+
   (set-repl-handler! 'ess-r-mode #'+ess/open-r-repl)
   (set-repl-handler! 'ess-julia-mode #'+ess/open-julia-repl)
-  (set-lookup-handlers! '(ess-r-mode ess-julia-mode)
+  (set-lookup-handlers! 'ess-julia-mode
     :documentation #'ess-display-help-on-object)
 
   (set-evil-initial-state! 'ess-r-help-mode 'normal)