Empty PATH_INFO causes blank SCRIPT_NAME

[chrisw]

Take the following Apache config snippet:

RewriteEngine On
WSGIScriptAlias /project /django/project/bin/django.wsgi

This results in mod_rewrite setting the SCRIPT_URL environment variable.

The code at ​http://code.djangoproject.com/browser/django/tags/releases/1.1.1/django/core/handlers/base.py#L204:

    script_url = environ.get('SCRIPT_URL', u'')
    if not script_url:
        script_url = environ.get('REDIRECT_URL', u'')
    if script_url:
        return force_unicode(script_url[:-len(environ.get('PATH_INFO', ''))])
    return force_unicode(environ.get('SCRIPT_NAME', u''))

...behaves incorrectly when, in the above example, /project is requested from Apache.

The problem is when PATH_INFO is empty, as it is in this case. Python
has no notion of positive or negative zero (;-)) so we end up returning
script_url[:0]. This results in request.META['SCRIPT_NAME']being set to '', which in turn results in urls being generated incorrectly.

A workaround for this is to add the following rewrite rule before !WSGIScriptAlias:

RewriteRule ^/project$ /project/ [R]

This bug is potentially related to #9435, but this is ticket describes a real world problem that I believe has bitten more people than just me...

A solution for this could well just be to change the section to:

    if script_url:
        path_info = environ.get('PATH_INFO', '')
        if path_info:
            script_url = script_url[:-len(path_info)]
        return force_unicode(script_url)
    return force_unicode(environ.get('SCRIPT_NAME', u''))

...but I have no idea where to go about writing a test.

[Ramiro Morales]

(reformatted description, please use the Preview button before submitting a ticket)