Note: As of 2015 ESS for company-mode is a preferred completion mechanism for ESS.

From version 12.03 ESS integrates out of the box with auto-complete package.

Three sources ‘ac-source-R-args’, ‘ac-source-R-objects’ and ‘ac-source-R’ are included in ESS distribution. The latest combines previous two and makes them play nicely together.






From ESS 12.09 auto-complete is activated by default if you have auto-complete package installed. See the documentation of `ess-use-auto-complete` variable for more.

This activates ‘ac-source-R in both ESS and iESS buffers. If you want AC only in your ESS buffers do:

(setq ess-use-auto-complete 'script-only)

Quick help

ESS provides AC help both for arguments and objects (default keys: `C-?` or `<f1>`)

You can bind `M-h` to display quick help pop-ups as in screen-shots above (requires a fairly recent version of AC

(define-key ac-completing-map (kbd "M-h") 'ac-quick-help)

Movement keys

Ac binds M-n, and M-p for navigation in the completion menu, which might be inconvenient if you want it to use in the inferior R. Bind it to something else:

(define-key ac-completing-map "\M-n" nil) ;; was ac-next
(define-key ac-completing-map "\M-p" nil) ;; was ac-previous
(define-key ac-completing-map "\M-," 'ac-next)
(define-key ac-completing-map "\M-k" 'ac-previous)

Completion keys

When selecting completion candidates the return key inserts the selected candidate. This can be a problem any time completion candidates are triggered and you want to insert a new line, because pressing return will complete the selected candidate rather than insert a new line as intended. One solution is to remove the binding of ac-complete to the return key”

(define-key ac-completing-map "\r" nil)

Optionally, you may wish to bind ac-complete to tab:

(define-key ac-completing-map "\t" 'ac-complete)

With recent versions of auto-complete you may need to set

 (define-key ac-completing-map [tab] 'ac-complete)
 (define-key ac-completing-map [return] nil)



Example of dark config as in the snapshot:

(set-face-attribute 'ac-candidate-face nil   :background "#00222c" :foreground "light gray")
(set-face-attribute 'ac-selection-face nil   :background "SteelBlue4" :foreground "white")
(set-face-attribute 'popup-tip-face    nil   :background "#003A4E" :foreground "light gray")

Misc customization

You can play with AC settings to adjust the completion to your needs:

      ;; ac-auto-show-menu 1
      ;; ac-candidate-limit nil
      ;; ac-delay 0.1
      ;; ac-disable-faces (quote (font-lock-comment-face font-lock-doc-face))
      ;; ac-ignore-case 'smart
      ;; ac-menu-height 10
      ;; ac-quick-help-delay 1.5
      ;; ac-quick-help-prefer-pos-tip t
      ;; ac-use-quick-help nil

For some more tips see this comment

EmacsSpeaksStatistics AutoComplete