How do I query what files need to be recompiled?

[Ahmon Dancy]

http://www.cliki.net/asdf has this FAQ:

Q: How do I query what files need to be recompiled?

A: With ASDF 3, you can 
(asdf:required-components system :force nil
:force-not nil :keep-component 'asdf:cl-source-file :keep-operation
'asdf:compile-op)

However, with ASDF 3.1.6, I find that this does not work as
advertised:


;;; system1.asd
(asdf:defsystem :system1
    :serial t
    :default-component-class asdf:cl-source-file.cl
    :components
    ((:file "one")
     (:file "two")
     (:file "three")))

cl-user(8): (asdf:compile-system :system1)
t

cl-user(9): (asdf:required-components :system1 
              :force nil :force-not nil
                                       :keep-component 'asdf:cl-source-file :keep-operation 'asdf:compile-op)
(#<asdf/lisp-action:cl-source-file.cl "system1" "one"> #<asdf/lisp-action:cl-source-file.cl "system1" "two"> #<asdf/lisp-action:cl-source-file.cl "system1" "three">)


Is there a new way to achieve the same goal?