util.lisp

(defun make-upload-filename ()
  (etypecase *upload-filename-generator* 
    ;; the old behaviour.
    (null t)
    ;; the new behaviour.
    ((or symbol function) 
     (lambda (&rest args)
       (let ((filename (apply *upload-filename-generator* args)))
         (when *file-upload-hook*
           (funcall *file-upload-hook* filename))
         filename)))
    (directory-pathname
     (lambda (&rest args &key file-name)
       (let ((filename (make-pathname :name file-name
                                      :directory *upload-filename-generator*)))
         (when *file-upload-hook*
           (funcall *file-upload-hook* filename))
         filename)))))

(deftype directory-pathname ()
  '(and pathname (satisfies cl-fad:directory-pathname-p)))

(defun make-upload-filename-generator ()
  (etypecase *upload-filename-generator* 
    ;; the old behaviour.
    (null (lambda (&rest args)
            (declare (ignore args))
            (funcall #'make-tmp-file-name)))
    ;; the new behaviour.
    ((or symbol function) 
     (lambda (&rest args)
       (let ((filename (apply *upload-filename-generator* args :allow-other-keys t)))
         (when *file-upload-hook*
           (funcall *file-upload-hook* filename))
         filename)))))

This looks good - One more thing - The file-upload-hook invocation should be moved out of make-tmp-file-name and called from the function that is returned from make-upload-filename-generator, something like;

(let ((make-filename (ecase ...)))
(lambda (&rest args)
(let ((filename (funcall make-filename args)))
(when file-upload-hook
(funcall ..))
filename)))

i.e. don't spread the hacky file-upload-hook throughout the code if it can be localized to one place.

Thanks,
Hans