generate-tags-file-on-save.el

(defun generate-project-tags-table () (interactive)
       (projectile-with-default-dir (projectile-project-root)
         (start-process "ctags" "ctags" "ctags" "-Re" ".")))

(defun generate-and-then-load-project-tags-table () (interactive)
       (if (projectile-project-p)
           (let ((process (generate-project-tags-table)))
             (set-process-sentinel process (lambda (_process event)
                                             (if (string-match-p "finished" event)
                                                 (visit-project-tags-table)))))))

(add-hook 'after-save-hook 'generate-and-then-load-project-tags-table)