Fix for subtle bug from 5c8f9c52e3

Change-Id: If2bd1d4a850936b2e575a96073c116a8b9522602

swift/common/wsgi.py

@@ -249,10 +249,6 @@ class WSGIContext(object):
     """
     def __init__(self, wsgi_app):
         self.app = wsgi_app
-        # Results from the last call to self._start_response.
-        self._response_status = None
-        self._response_headers = None
-        self._response_exc_info = None
 
     def _start_response(self, status, headers, exc_info=None):
         """
@@ -267,6 +263,9 @@ class WSGIContext(object):
         """
         Ensures start_response has been called before returning.
         """
+        self._response_status = None
+        self._response_headers = None
+        self._response_exc_info = None
         resp = self.app(env, self._start_response)
         # if start_response has been called, just return the iter
         if self._response_status is not None:

test/unit/common/test_wsgi.py

@@ -238,5 +238,25 @@ class TestWSGI(unittest.TestCase):
         self.assertEquals(e['PATH_INFO'], '/override')
 
 
+class TestWSGIContext(unittest.TestCase):
+
+    def test_app_call(self):
+        statuses = ['200 Ok', '404 Not Found']
+
+        def app(env, start_response):
+            start_response(statuses.pop(0), [('Content-Length', '3')])
+            yield 'Ok\n'
+
+        wc = wsgi.WSGIContext(app)
+        r = Request.blank('/')
+        it = wc._app_call(r.environ)
+        self.assertEquals(wc._response_status, '200 Ok')
+        self.assertEquals(''.join(it), 'Ok\n')
+        r = Request.blank('/')
+        it = wc._app_call(r.environ)
+        self.assertEquals(wc._response_status, '404 Not Found')
+        self.assertEquals(''.join(it), 'Ok\n')
+
+
 if __name__ == '__main__':
     unittest.main()