[Web-SIG] Proposal: Handling POST forms in WSGI

[Ian Bicking]

I've updated this specification in response to input, mostly changing 
language but not the meat of the specification itself:

http://wsgi.org/wsgi/Specifications/handling_post_forms
http://wsgi.org/wsgi/Specifications/handling_post_forms?action=diff

One thing that occurred to me is that wsgi.input might be a better 
container for the data than an environ key, like:

     fs = getattr(environ['wsgi.input'], 'cgi_FieldStorage', None)
     if fs is None: # parse and replace wsgi.input...

I actually have reason to want to generalize this, maybe like:

def parse_form(environ):
     # Check for POST, CONTENT_TYPE...
     decoded = getattr(environ['wsgi.input'], 'decoded', None)
     if decoded is not None:
         decoded_type, decoded_value = decoded
         if decoded_type == 'cgi.FieldStorage':
             return decoded_value
     decoded_value = cgi.FieldStorage(...)
     input = FakeInput(None, 'cgi.FieldStorage', decoded_value)
     environ['wsgi.input'] = input
     return decoded_value

class FakeInput(object):

     def __init__(self, file_body, decoded_type, decoded_value):
         self._body = file_body
         self.decoded = (decoded_type, decoded_value)
     def read(self, *args):
         if self._body is None:
             raise EOFError("wsgi.input has already been consumed to 
produce %r" % self.decoded)
         return self._body.read(*args)
     # other file methods...



This allows for internal WSGI requests with bodies like text/json to 
totally avoid serializing and deserializing.  In some cases there'd be 
exceptions raised (like this case), but in other cases you can lazily 
serialize to deal with intermediaries.

I don't know why this didn't occur to me, since I've actually been doing 
this in WSGIRemote, but I like it more than my current proposal.  If it 
sounds like a good idea to other people I'll drop the current proposal 
and create this more generalized proposal with a section on POST forms.


-- 
Ian Bicking | ianb at colorstudy.com | http://blog.ianbicking.org