Can I use ido-completing-read instead of completing-read everywhere?

Question

I'm a big fan of ido-mode, so much so that I would like to use it for things like describe-function or find-tag and so on, without having to write something like in "Can I get ido-mode-style completion for searching tags in Emacs?" for each one.

Both

(defalias completing-read ido-completing-read)

and

(setf 'completing-read 'ido-completing-read)

don't work, at least partly because ido-completing-read calls completing-read in its body, so any simple redefinition would result in infinite recursion.

In theory, it should be possible, since the first line of the docstring for ido-completing-read is "Ido replacement for the built-in completing-read." I've looked around a bit and can't seem to find anyone else who has attempted or succeeded at it.

I realize that Icicles probably provides something like this, and I may end up going with that anyway, but it is a bit more of a plunge than I care to take right now.

Thanks for any help.

Answer 1

Edit: This is now an Emacs package available from MELPA. It has been expanded into a full-fledged minor mode. Development happens on GitHub.

Original post:

Here is my refinement of Jacobo's answer. Credit to him for the original magic. I've added an override variable, which you can use to prevent the use of ido-completing-read in specific functions. I have also added a check that uses the original completing-read if there are no completions (This happens occasionally, for example in org-remember-apply-template from org-mode, which breaks with Jacobo's original advice).

(defvar ido-enable-replace-completing-read t
  "If t, use ido-completing-read instead of completing-read if possible.

Set it to nil using let in around-advice for functions where the
original completing-read is required.  For example, if a function
foo absolutely must use the original completing-read, define some
advice like this:

(defadvice foo (around original-completing-read-only activate)
  (let (ido-enable-replace-completing-read) ad-do-it))")

;; Replace completing-read wherever possible, unless directed otherwise
(defadvice completing-read
  (around use-ido-when-possible activate)
  (if (or (not ido-enable-replace-completing-read) ; Manual override disable ido
          (boundp 'ido-cur-list)) ; Avoid infinite loop from ido calling this
      ad-do-it
    (let ((allcomp (all-completions "" collection predicate)))
      (if allcomp
          (setq ad-return-value
                (ido-completing-read prompt
                               allcomp
                               nil require-match initial-input hist def))
        ad-do-it))))

Oh, and for using ido in M-x, use amx.