paste.util.mimeparse.best_match compatibility with '*' mime type

[amol]

Copying here the content of email I sent to the TG2 ML as it has been asked to me to open a ticket about this issue.

As RFC 2616 media range in HTTP_ACCEPT should be specified as

media-range = ( "*/*"

| ( type "/" "*" ) | ( type "/" subtype ) ) *( ";" parameter )

so when "all" is meant "*/*" should be passed, but some user agents, like the facebook external link retriever pass '*' instead of '*/*' this makes paste.util.mimeparse.best_match crash on paste.util.mimeparse.parse_mime_type

paste.util.mimeprase.best_match is used by Turbogears to detect which template to render, and so each TG2 application crashes when contacted by facebook.

A solution is to change paste.util.mimeparse.parse_mime_type to support the '*' syntax by adding

if parts[0].strip() == '*':

parts[0] = '*/*'

just before

(type, subtype) = parts[0].split("/")

this fixes the problem and I have already patched all my deployed TG2 apps, but I think that a more general fix might be good and also people at paste and mimeparse might be interested in having the patch. (This happens with Paste-1.7.2 at least)

The working version of the parse_mime_type method is the following one:

def parse_mime_type(mime_type):

"""Carves up a mime_type and returns a tuple of the

(type, subtype, params) where 'params' is a dictionary of all the parameters for the media range. For example, the media range 'application/xhtml;q=0.5' would get parsed into:

('application', 'xhtml', {'q', '0.5'}) """

parts = mime_type.split(";") params = dict([tuple([s.strip() for s in param.split("=")])\

for param in parts[1:] ])

if parts[0].strip() == '*':

parts[0] = '*/*'

(type, subtype) = parts[0].split("/") return (type.strip(), subtype.strip(), params)

[natedub]

The paste guys have an  issue in their trac for this, and  a fix in the paste trunk as of 13 months ago — and it still hasn't been released.

Guess I'll monkeypatch for now. Sigh.

[brondsem]

I'm encountering this exception fairly frequently. And #2487 describes the same problem, I think.

It looks like Paste 1.7.3 was release recently, and includes some mimeparse fixes.  http://pythonpaste.org/news.html#id1

As a bit of a side note: very frequently our controllers only have one @expose type, so in lookup_template_engine, if len(self.engines) == 1, that content_type could be used and best_match does not have to be called at all.

[chrisz]

Does this only affect TG 2.0.x? If not, the milestone should be set to 2.1.

[brondsem]

It effects 2.1b1 also.

[chrisz]

This has been  fixed now in the paste trunk.