(add-to-list 'completion-at-point-functions 'foo-completion)
;; it is now (foo-completion lisp-completion-at-point t)
Place your point at the end of 'aaaa and you try to complete. I am
in my message buffer. Which means the completion is called twice. I hope
this is not an intended behavior, as it might seriously interfere with
custom completion. For example I might want to have a different behavior
on the second consequent invocation of the completion (give a message,
modify the candidates etc).
Second problem is that if the completion is sole, the handling is not
passed over. For example after 'truncat I am getting a message "Sole
completion" and the lisp-completion-at-point is not reached at all. I
believe it's not how it should work.
In all the rest, new completion system is virtually perfect, thanks.