Question

How to code auto-complete to immediately trigger when there is only one unique option?
(or, when there are several options, but they all have the same base)

(eval-exp_[point-is-here]_)

Autocomplete offers:

(eval-expression
(eval-expression-print-format)

Now when it hits a unique option, wouldn’t it be great if it would just immediately complete to (eval-expression, and then if we would type "-" that it would immediately choose print-format?

Even if there would be then 2 options, you can see in the following example that you would only need "-p" to complete:

(eval-expression-print-format)
(eval-expression-something-else)

Is this behavior possible in Emacs?

Answer 1

It realizes required behavior:

(defadvice ac-inline-show (after eab-ac-expand activate)
  (if (> (length ac-candidates) 1)
      (let ((ac-common-part (try-completion ac-prefix ac-candidates)))
        (ac-expand-common))
    (progn
      (ac-expand-string ac-common-part)
      (ac-inline-hide)))
  (setq eab-last-selected-candidate ac-selected-candidate))

For deactivate:

(ad-remove-advice 'ac-inline-show 'after 'eab-ac-expand)
(ad-deactivate 'ac-inline-show)

EDIT:

I experimented with workflow and found one way to cancel miswritings. As an example you prints lam and it is expanded as lambda but you adds extra bd accidentally and gets lambdabd. So I setup

(global-set-key (kbd "C-<tab>") '(lambda () (interactive) (flet ((ac-candidates () `(,eab-last-selected-candidate))) (ac-fuzzy-complete)) (ac-expand)))

and use it: lambdabd becomes lambda and you can continue as usual.

EDIT2:

There was one downside of the solution: “it slows down a bit when it does the fuzzy”. It is fixed by narrowing ac-candidates to eab-last-selected-candidate for ac-fuzzy-complete. Now it’s fast!