Port ido-file-extension-order

[ThibautVerron]

It would be nice to have a feature similar to ido-file-extension-order: it allows to specify a set of extensions which should be shown first in the file list. It is the same idea as "boring files", except that the unwanted extensions are still shown if needed, just further down the list.

The following seems to do the job on a system where ido is available:

(defun ivy-sort-file-function-using-ido-extensions (a b)
  (if (and (boundp 'ido-file-extensions-order)
           ido-file-extensions-order)
      (ido-file-extension-lessp a b)
    (ivy-sort-file-function-default a b)))

(setq ivy-sort-functions-alist
      (cons (cons 'read-file-name-internal 'ivy-sort-file-function-using-ido-extensions)
            (cdr ivy-sort-functions-alist)))

It is quite unefficient because it will test for ido-file-extensions-order at each comparison... so merely a proof of concept.

By the way, is there a good reason for functions in ivy-sort-functions-alist to be restricted to 3 values?

[abo-abo]

It is quite unefficient because it will test for ido-file-extensions-order at each comparison... so merely a proof of concept.

Could be good enough. The sorting is performed only once per collection, i.e. just after you enter a directory.

By the way, is there a good reason for functions in ivy-sort-functions-alist to be restricted to 3 values?

I don't understand what you mean here.

[ThibautVerron]

Oh, my bad, I forgot the end of the sentence. I meant the configuration interface for the variable:

    :value-type (choice
                 (const :tag "Plain sort" string-lessp)
                 (const :tag "File sort" ivy-sort-file-function-default)
                 (const :tag "No sort" nil)))

[abo-abo]

Feel free to PR with a new sorting option.

[ThibautVerron]

The question was rather "why isn't it a free-form field"? For example if a user wants to implement his own comparison function, he has to modify the variable in elisp, he can't use customize.

As for the ido-sort thing, I'll try to submit a PR this week-end.

[abo-abo]

why isn't it a free-form field

Should have just said so:)

[abo-abo]

It is quite unefficient because it will test for ido-file-extensions-order at each comparison... so merely a proof of concept.

Why exactly should this be inefficient? The sorting in ivy-sort-functions-alist is performed only once per current directory change. Just test the code as-is and open a PR. The sorting doesn't have to be on by default.

[ThibautVerron]

Well, sorting requires at least as many comparisons as there are files, and since the result of this test is the same for every comparison, I imagined it would be nicer to factor it out of the comparison function. But for reasonable number of files, the overhead should be neglectible. The code appears to be working as-is, I'll make the PR now (sorry, I had less time than I thought in the previous weeks). Is it ok that the code depends on ido?