Fixed Connection side effects and add into breaking changes.

UPGRADE-v2.0.md

@@ -47,3 +47,36 @@
   class Dog(ObjectType, interfaces=[Pet]):
       name = String()
   ```
+
+## Breaking Changes
+
+* Node types no longer have a `Connection` by default.
+  In 2.0 and onwoards `Connection`s should be defined explicitly.
+  
+  Before:
+
+  ```python
+  class User(ObjectType):
+      class Meta:
+          interfaces = [relay.Node]
+      name = String()
+    
+  class Query(ObjectType):
+      user_connection = relay.ConnectionField(User)
+  ```
+
+  With 2.0:
+
+  ```python
+  class User(ObjectType):
+      class Meta:
+          interfaces = [relay.Node]
+      name = String()
+  
+  class UserConnection(relay.Connection):
+      class Meta:
+          node = User
+
+  class Query(ObjectType):
+      user_connection = relay.ConnectionField(UserConnection)
+  ```

graphene/relay/connection.py

@@ -98,10 +98,7 @@ class IterableConnectionField(Field):
     @property
     def type(self):
         type = super(IterableConnectionField, self).type
-        if is_node(type):
-            connection_type = type.Connection
-        else:
-            connection_type = type
+        connection_type = type
         assert issubclass(connection_type, Connection), (
             '{} type have to be a subclass of Connection. Received "{}".'
         ).format(self.__class__.__name__, connection_type)