[Web-SIG] WSGI tests

[Phillip J. Eby]

At 11:47 PM 9/28/04 -0500, Ian Bicking wrote:

>Then there's the lint middleware.  This doesn't modify the request in any 
>way (though it does wrap start_response and other objects).

The wrapper is broken: 'exc_info = args[3]' should be 'exc_info = args[2]'.


>   It just checks various things; right now it mostly checks that required 
> environmental variables are there and that everything is of the right type.

Some of the variables you're checking for are not actually required any 
more; see

     http://www.python.org/peps/pep-0333.html#environ-variables

for details.

Also, your header checks are requiring non-duplicated headers, but 
duplicate header names are in fact allowed, per discussion on the 
list.  But, this isn't explicitly stated in the spec, so I should fix that.

I'm also not positive that a Content-Type header is absolutely required, 
e.g. for redirects.  I guess I should dig up the HTTP spec on this point.


>   It doesn't test any of the more subtle aspects of WSGI, or test any 
> failure cases.

Apart from the fact that it doesn't always return an iterable, the lint app 
is WSGI compliant, but "overprotective", in that it requires things not 
required by the spec.

Other than those nits, it's a pretty nice piece of middleware and I'll 
probably use it to help in writing a WSGI "reference library".


>   It doesn't test the exc_info stuff either; I haven't kept up, and I 
> only partly understand the motivation there.

exc_info should be a three-element tuple containing a type, an instance of 
the type, and a traceback object.  If start_response() is called more than 
once, it's a fatal error not to include exc_info (because the only time 
it's valid to call start_response() a second time is if an error occurred 
while you were writing or yielding output).  If exc_info is supplied and 
headers have already been sent to the server, the server *must* raise an 
error, and *should* raise the supplied exc_info triplet.  So, some of these 
things can be tested by your 'lint' program.

See also:

     http://www.python.org/peps/pep-0333.html#the-start-response-callable

from paragraph 7 on.