Re: url-retrieve may cause hang

[Stefan Monnier <monnier@iro.umontreal.ca>]

> - There is no protocol for letting the callback know that retrieval
>   failed.  Without this patch, the caller would immediately get an
>   error, but now the error is signalled in the sentinel.  One solution
>   would be to introduce an :error argument to the callback, similar to
>   the :redirect one.

Yes, this is a basic flaw in the design.  It would be good to fix it before
the release.  Your suggestion of extending the :redirect to include other
info sounds good.  Basically, the callback should be called with 2 args: the
list CBARGS, and a "status" which can be nil (indicating the absence of
anything noteworthy), or (:redirect URL), or (:error ERROR) where ERROR is
of the form such that it can be used in (signal (car ERROR) (cdr ERROR)).


        Stefan