How can I start swiper with an initial filter?

Question

I'd like to start swiper with a filter pre-set on the search -- as if I'd entered a search expression and then used S-SPC (ivy-restrict-to-matches) to clear the query space to narrow the results down further.

I can use

(swiper "something to search on here")

but I still see something to search on here in the minibuffer. How can I get that to go away programmatically?

---

My use-case is a simple way to navigate functions defined in a file. I defined a regexp that matches the beginning of functions up to the function name -- I'd like to match on this name.

Answer 1

It's a bit tricky, since you can't call anything after read-from-minibuffer (called by ivy-read called by swiper) until it returns. However, there's a visible function swiper--update-input-ivy that's called in post-command-hook. You can advice this function. It could also be possible to advice ivy--exhibit (it's always in the minibuffer's post-command-hook), but swiper--update-input-ivy will have less side-effects.

(defun swiper-ivy-restrict-to-matches-once (&rest r)
  (ivy-restrict-to-matches)
  (advice-remove
   'swiper--update-input-ivy
   'swiper-ivy-restrict-to-matches-once))

(defun swiper-for-defun ()
  (interactive)
  (advice-add
   'swiper--update-input-ivy
   :after 'swiper-ivy-restrict-to-matches-once)
  (swiper "defun"))

New solution due to an update in API

(defun swiper-for-defun ()
  (interactive)
  (swiper--ivy
   (cl-remove-if-not
    (lambda (x)
      (string-match "^ (defun" x))
    (swiper--candidates))))