If you’re not using projectile, but you would like to be able to perform interactive, search-as-you-type, recursive searches through the current project, this is pretty easy to do if you have counsel and find-file-in-project installed.

Add the following Emacs Lisp to your init:

(defun cpb/counsel-ag-in-project ()
  "Use `ffip' and `counsel-ag' for quick project-wide text searching."
  (interactive)
  (let ((project-root (ffip-project-root)))
    ;; if ffip could not find project-root, it will already have
    ;; shown an error message. We only have to check for non-nil.
    (if project-root
        (counsel-ag nil project-root nil
                    (format "Search in PRJ %s" project-root)))))

(global-set-key (kbd “C-c s”) ‘cpb/counsel-ag-in-project)

This function, which I have bound to ctrl-c s, finds the project root using find-file-in-project's function for this, and then invokes the handy counsel-ag on its result.