[Zope-dev] DAV collections, index_html, and HEAD

[Karl Anderson]

Objects that inherit from Folder (and therefore from Collection) and
also have an index_html that's a Python method (or othewise
nonvanilla, presumably) return a 405 (Method Not Allowed) for HTTP
HEAD requests.

Zope 2.5.1 raises on line 57 of Collection.py.  The object raises if
its index_html member doesn't have a HEAD attribute.

Surely it's a bug to only give HEAD for objects that return an
index_html via hasattr/getattr.  What about getitem,
__bobo_traverse__, and __call__?  Shouldn't we find the object to HEAD
via ZPublisher?  And aren't we bypassing the access control checks,
anyway?

Would it be a good idea to try and make up a HEAD response for
arbitrary attributes that don't support it (such as Python methods)?
Perhaps by publishing them internally, and picking whatever we can
from RESPONSE, computing Content-Length from the returned stream if
necessary?  It's inefficient, but at least it's cache-friendly... and
better for tools (er, linbot) that assume that if it can't be found
via HEAD, it isn't there.

Excerpt from Collection.HEAD():

        # Note that we are willing to acquire the default document
        # here because what we really care about is whether doing
        # a GET on this collection / would yield a 200 response.
        if hasattr(self, 'index_html'):
            if hasattr(self.index_html, 'HEAD'):
                return self.index_html.HEAD(REQUEST, RESPONSE)
            raise 'Method Not Allowed', (
                  'Method not supported for this resource.'
                  )
        raise 'Not Found', 'The requested resource does not exist.'





persephone ~/tmp= telnet viii.dclxvi.org 80
Trying 206.163.69.253...
Connected to viii.dclxvi.org.
Escape character is '^]'.
HEAD /blog HTTP/1.0
HEAD /blog HTTP/1.0


HTTP/1.1 405 Method Not Allowed
Date: Thu, 06 Jun 2002 02:22:40 GMT
Server: Apache/1.3.12 (Unix) mod_ssl/2.6.6 OpenSSL/0.9.5a
Bobo-Exception-File: /usr/local/zope/2-5-1/lib/python/webdav/Collection.py
Bobo-Exception-Line: 57
Bobo-Exception-Type: Method Not Allowed
Bobo-Exception-Value: bobo exception
Connection: close
Content-Location: http://viii.dclxvi.org/blog/
Ms-Author-Via: DAV
X-Powered-By: Zope (www.zope.org), Python (www.python.org)
Content-Length: 2106
Content-Type: text/html


-- 
Karl Anderson      kra@monkey.org           http://www.monkey.org/~kra/