move url matching after opening session

src/flask/ctx.py

@@ -347,8 +347,8 @@ class RequestContext(object):
         of the request.
         """
         try:
-            url_rule, self.request.view_args = self.url_adapter.match(return_rule=True)
-            self.request.url_rule = url_rule
+            result = self.url_adapter.match(return_rule=True)
+            self.request.url_rule, self.request.view_args = result
         except HTTPException as e:
             self.request.routing_exception = e
 
@@ -381,9 +381,6 @@ class RequestContext(object):
 
         _request_ctx_stack.push(self)
 
-        if self.url_adapter is not None:
-            self.match_request()
-
         # Open the session at the moment that the request context is available.
         # This allows a custom open_session method to use the request context.
         # Only open a new session if this is the first time the request was
@@ -395,6 +392,9 @@ class RequestContext(object):
             if self.session is None:
                 self.session = session_interface.make_null_session(self.app)
 
+        if self.url_adapter is not None:
+            self.match_request()
+
     def pop(self, exc=_sentinel):
         """Pops the request context and unbinds it by doing that.  This will
         also trigger the execution of functions registered by the