Remove proxying of resources_fs, and add a unittest that exposes the problem

[PLAT-191]

lms/djangoapps/courseware/tests/test_module_render.py

-# -*- coding: utf-8 -*-
 """
 Test for lms courseware app, module render unit
 """
@@ -19,6 +18,7 @@ from courseware.module_render import hash_resource
 from xblock.field_data import FieldData
 from xblock.runtime import Runtime
 from xblock.fields import ScopeIds
+from xblock.core import XBlock
 from xmodule.lti_module import LTIDescriptor
 from xmodule.modulestore.django import modulestore
 from xmodule.modulestore.tests.django_utils import ModuleStoreTestCase
@@ -43,6 +43,14 @@ from lms.lib.xblock.runtime import quote_slashes
 from xmodule.modulestore import ModuleStoreEnum
 
 
+class PureXBlock(XBlock):
+    """
+    Pure XBlock to use in tests.
+    """
+    pass
+
+
+@ddt.ddt
 @override_settings(MODULESTORE=TEST_DATA_MIXED_MODULESTORE)
 class ModuleRenderTestCase(ModuleStoreTestCase, LoginEnrollmentTestCase):
     """
@@ -163,6 +171,17 @@ class ModuleRenderTestCase(ModuleStoreTestCase, LoginEnrollmentTestCase):
         self.assertEquals(403, response.status_code)
         self.assertEquals('Unauthenticated', response.content)
 
+    @ddt.data('pure', 'vertical')
+    @XBlock.register_temp_plugin(PureXBlock, identifier='pure')
+    def test_rebinding_same_user(self, block_type):
+        request = self.request_factory.get('')
+        request.user = self.mock_user
+        course = CourseFactory()
+        descriptor = ItemFactory(category=block_type, parent=course)
+        field_data_cache = FieldDataCache([self.toy_course, descriptor], self.toy_course.id, self.mock_user)
+        render.get_module_for_descriptor(self.mock_user, request, descriptor, field_data_cache, self.toy_course.id)
+        render.get_module_for_descriptor(self.mock_user, request, descriptor, field_data_cache, self.toy_course.id)
+
     def test_hash_resource(self):
         """
         Ensure that the resource hasher works and does not fail on unicode,

lms/lib/xblock/runtime.py

@@ -266,11 +266,3 @@ class LmsModuleSystem(LmsHandlerUrls, LmsCourse, LmsUser, ModuleSystem):  # pyli
         )
         services['fs'] = xblock.reference.plugins.FSService()
         super(LmsModuleSystem, self).__init__(**kwargs)
-
-    # backward compatibility fix for callers not knowing this is a ModuleSystem v DescriptorSystem
-    @property
-    def resources_fs(self):
-        """
-        Return what would be the resources_fs on a DescriptorSystem
-        """
-        return getattr(self, 'filestore', None)