draft-murchison-webdav-prefer

All,

I'd like to get some feedback on draft-murchison-webdav-prefer 
<http://tools.ietf.org/html/draft-murchison-webdav-prefer-07> , 
specifically Section 3 
<http://tools.ietf.org/html/draft-murchison-webdav-prefer-07#section-3> 
(the rest of the document is truly WebDAV specific).  Per a request from 
the Apple calendar client folks, we'd like to extend 
Prefer:return=representation 
<http://tools.ietf.org/html/rfc7240#section-4.2> to apply to a 
conditional PUT request that fails with a 412 (Precondition Failed) 
response.  This eliminates the need for a subsequent GET to fetch the 
current representation of a resource that failed to update because of a 
validator mismatch.  I view this as analogous to Get + If-Range.

Does anyone see any issues with this new behavior?  Does it violate 
RFC7230-7232 in any way?  Are we allowed to extended 
return=representation to failure responses (RFC7240 only discusses 
success responses)?  Are there any other sane interpretations of a 412 
response with a Preference-Applied:representation header field which 
would cause ambiguity for the client?

Thanks and Happy Holidays!
Ken

-- 
Kenneth Murchison
Principal Systems Software Engineer
Carnegie Mellon University