bug#21644: 24.4; completing-read acts differently on functional collection

[Dmitry Gutov <dgutov@yandex.ru>]

On 10/08/2015 01:13 PM, Oleh Krehel wrote:

> I can reproduce this as well, although "TAB RET" works where "RET"
> doesn't. I attach a patch with a fix. If someone can check it I can push
> it. The patch doesn't solve all the intricacies of
> `completion-ignore-case' that were mentioned in that function's
> comments, just this specific use case.

Is there really a bug here?

The example code didn't handle `test-completion' (the case when ALL 
would be `lambda').

With this definition, the behavior is the same in either case:

(defun collection-as-function (collection)
   "Return a function equivalent to COLLECTION.

The returned function will work equivalently to COLLECTION when
passed to `all-completions' and `try-completion'."
   (if (functionp collection)
       collection
     ;; Capture collection in a closure
     (lambda (string pred all)
       (funcall
        (cond
         ((eq all 't)
          #'all-completions)
         ((eq all 'lambda)
          #'test-completion)
         (t
          #'try-completion))
        string collection pred))))