To enable Emacs to speak to R, we need to use the Emacs Speaks Statistics (ESS) Package. Setting this up is pretty easy and reading the manual should suffice, mostly. The one thing that is important to note is that when telling ESS where to look for the R process, you should choose the Rterm.exe binary. Set the inferior-ess-r-program to point to the binary like so:

(setq inferior-ess-r-program "C:/path/to/your/R/installation/bin/Rterm.exe")

Note that you either have to escape the backslashes from the path (i.e., you have to have two backslashes in a row C:\\path\\tofile), or use forward slashes (as in the example above).

Current versions of Emacs come with Tree-sitter support. However, to install the language grammars that then allow Emacs to parse the files, you will need a working compiler on your system. Specifically, you need to have a C-compiler (the cc command specifically) that Emacs can use to compile the sources from the grammars. We ultimately got this accomplished using the MSYS2.

Follow the instructions on https://www.msys2.org/, including the installation of the GCC compiler from UCRT64 environment:

pacman -S mingw-w64-ucrt-x86_64-gcc

Add the path to the compilers to the environment variables: Go to the Start menu, search for "environment variables", then edit the path to include the path to the compiler binaries. If you are unsure where to find the cc.exe file, you can use the which cc command in the UCRT64 environment where you installed GCC. Make sure you properly reference the path by changing forward slashes to backslashes.

While Tree-sitter support is available in Emacs, the user needs to install the language grammars. This can be accomplished with something like this:

(setq treesit-language-source-alist
   '((bash "https://github.com/tree-sitter/tree-sitter-bash")
     (cmake "https://github.com/uyha/tree-sitter-cmake")
     (css "https://github.com/tree-sitter/tree-sitter-css")
     (elisp "https://github.com/Wilfred/tree-sitter-elisp")
     (go "https://github.com/tree-sitter/tree-sitter-go")
     (html "https://github.com/tree-sitter/tree-sitter-html")
     (javascript "https://github.com/tree-sitter/tree-sitter-javascript" "master" "src")
     (json "https://github.com/tree-sitter/tree-sitter-json")
     (make "https://github.com/alemuller/tree-sitter-make")
     (markdown "https://github.com/ikatyang/tree-sitter-markdown")
     (python "https://github.com/tree-sitter/tree-sitter-python")
     (r "https://github.com/r-lib/tree-sitter-r")
     (toml "https://github.com/tree-sitter/tree-sitter-toml")
     (tsx "https://github.com/tree-sitter/tree-sitter-typescript" "master" "tsx/src")
     (typescript "https://github.com/tree-sitter/tree-sitter-typescript" "master" "typescript/src")
     (yaml "https://github.com/ikatyang/tree-sitter-yaml")))

(mapc #'treesit-install-language-grammar (mapcar #'car treesit-language-source-alist))

This is taken from Mastering Emacs, I just added the the link to the tree-sitter-r repository. You don't need to execute this code every time you start Emacs, so it should not go into the init file. I have saved the code in a separate tree-sitter-grammar-install.el file that I can open and run when I need to.

If the install of MSYS2 worked without a hitch, then Tree-sitter grammars should be installed into a sub-directory of the .emacs.d directory.

Like Tree-sitter, the support for the language server protocol is baked into emacs with the eglot package. The main sticking point here was that we first added the path to Rterm.exe to the eglot-server-programs association list, but this should be Rscript.exe. In the end, the following code in the students init file worked:

;; eglot
(use-package eglot
  :ensure t
  :init
  (add-hook 'R-mode-hook 'eglot-ensure)
  :config
  (add-to-list
   'eglot-server-programs
   '((R-mode ess-r-mode) . ("C:\\Program Files\\R\\R-4.4.1\\bin\\x64\\Rscript.exe" "--slave" "-e" "languageserver::run()"))
   ))

Again, the backslashes have to be escaped, or forward slashes must be used.