Emacs

Air provides first class support for Emacs, which supports the Language Server Protocol via the eglot and lsp-mode modes.

Installation

eglot

eglot is distributed with Emacs

Adapt your init.el with the following configuration:

(add-to-list
  'eglot-server-programs
  '(ess-r-mode . ("air" "language-server")))

;; Start LSP when ess-r-mode is activated
(add-hook 'ess-r-mode-hook 'eglot-ensure)

lsp-mode

lsp-mode can be installed from MELPA, see https://emacs-lsp.github.io/lsp-mode/page/installation

If the languageserver R package is installed, lsp-mode will use it in ess-r-mode by default. To use the Air language server without the language server provided by the languageserver R package, adapt your init.el with the following configuration:

;; Disable languageserver entirely
(add-to-list 'lsp-disabled-clients 'lsp-r)

(lsp-register-client
  (make-lsp-client
    :new-connection (lsp-stdio-connection '("air" "language-server"))
    :major-modes '(ess-r-mode)
    :server-id 'lsp-r-air))

;; Start LSP when ess-r-mode is activated
(add-hook 'ess-r-mode-hook #'lsp-deferred)

To use Air in combination with languageserver, adapt your init.el with the following configuration.

  (lsp-register-client
   (make-lsp-client
    :new-connection (lsp-stdio-connection '("air" "language-server"))
    :major-modes  '(ess-r-mode)
    :server-id 'lsp-r-air
    :add-on? t
    :priority 1))

You will also need to add the following to your global and/or project-specific .Rprofile file to disable formatting by the languageserver package to avoid conflicts when using lsp-format-region:

options(
  languageserver.server_capabilities = list(
    documentFormattingProvider = FALSE,
    documentRangeFormattingProvider = FALSE
  )
)

If you encounter timeout errors when using lsp-mode in large projects, refer to the lsp-mode documentation on how to disable file watchers.

Features

Format on save

Emacs doesn’t have official support for formatting on save, but hooking into the save action is easy.

With eglot:

(defun my-eglot-format-on-save ()
  "Formats buffer with Eglot on save for specified modes."
  (when (member major-mode '(ess-r-mode))
    (eglot-format-buffer)))

(add-hook 'after-save-hook 'my-eglot-format-on-save))

With lsp-mode, from https://emacs-lsp.github.io/lsp-mode/page/main-features:

You can also trigger format on save by setting the variable lsp-format-buffer-on-save to a non-nil value. To select what major modes to format use lsp-format-buffer-on-save-list.

(setq lsp-format-buffer-on-save t)
(setq lsp-format-buffer-on-save-list '("ess-r-mode"))

Format document or region

• With eglot: Run M-x eglot-format to format the current buffer or selection.

• With lsp-mode: Run M-x lsp-format-buffer to format the current buffer or lsp-format-region to format the current selection.

Known Issues

• Attempting to format selection when multiple lines are selected seems not to be working, but selecting part or all a line in a multi-line expression will format that entire expression. This isssue occurs regardless of whether Air is used with Eglot or LSP-mode.