Add flag to stop swob from always using absolute location.

This is needed for SOS (along with patch
https://github.com/dpgoetz/sos/pull/37)
to work with swift 1.12 . By spec you should always use the absolute
location but this causes a problem with staticweb over a cdn using a
cname. Basically you want to be able to forward the browser to a
relative location instead of whatever full url the proxy server
thinks you are using.

Change-Id: I3fa1d415bf9b566be069458b838f7e65db0c4f39

doc/source/misc.rst

@@ -33,6 +33,16 @@ Utils
     :members:
     :show-inheritance:
 
+.. _swob:
+
+Swob
+====
+
+.. automodule:: swift.common.swob
+    :members:
+    :show-inheritance:
+    :special-members: __call__
+
 .. _acls:
 
 ACLs

swift/common/swob.py

@@ -1186,11 +1186,31 @@ class Response(object):
         return self.status_int // 100 == 2
 
     def __call__(self, env, start_response):
+        """
+        Respond to the WSGI request.
+
+        .. warning::
+
+            This will translate any relative Location header value to an
+            absolute URL using the WSGI environment's HOST_URL as a
+            prefix, as RFC 2616 specifies.
+
+            However, it is quite common to use relative redirects,
+            especially when it is difficult to know the exact HOST_URL
+            the browser would have used when behind several CNAMEs, CDN
+            services, etc. All modern browsers support relative
+            redirects.
+
+            To skip over RFC enforcement of the Location header value,
+            you may set ``env['swift.leave_relative_location'] = True``
+            in the WSGI environment.
+        """
         if not self.request:
             self.request = Request(env)
         self.environ = env
         app_iter = self._response_iter(self.app_iter, self._body)
-        if 'location' in self.headers:
+        if 'location' in self.headers and \
+                not env.get('swift.leave_relative_location'):
             self.location = self.absolute_location()
         start_response(self.status, self.headers.items())
         return app_iter

test/unit/common/test_swob.py

@@ -1034,6 +1034,19 @@ class TestResponse(unittest.TestCase):
         ''.join(resp(req.environ, start_response))
         self.assertEquals(resp.location, 'http://www.google.com/')
 
+    def test_location_no_rewrite_when_told_not_to(self):
+        def start_response(env, headers):
+            pass
+        req = swift.common.swob.Request.blank(
+            '/', environ={'SERVER_NAME': 'local', 'SERVER_PORT': 81,
+                          'swift.leave_relative_location': True})
+        del req.environ['HTTP_HOST']
+        resp = self._get_response()
+        resp.location = '/something'
+        # read response
+        ''.join(resp(req.environ, start_response))
+        self.assertEquals(resp.location, '/something')
+
     def test_app_iter(self):
         def start_response(env, headers):
             pass