get the raw DescriptorSystem, not the CombinedSystem when instantiating xmodules (TNL-1226)

get the raw DescriptorSystem, not the CombinedSystem when instantiating xmodules (TNL-1226)

quality fixes

remove trailing comma

common/lib/xmodule/xmodule/tests/__init__.py

@@ -94,7 +94,7 @@ def get_test_system(course_id=SlashSeparatedCourseKey('org', 'course', 'run')):
     """
     user = Mock(name='get_test_system.user', is_staff=False)
 
-    descriptor_system = get_test_descriptor_system(),
+    descriptor_system = get_test_descriptor_system()
 
     def get_module(descriptor):
         """Mocks module_system get_module function"""
@@ -107,7 +107,7 @@ def get_test_system(course_id=SlashSeparatedCourseKey('org', 'course', 'run')):
 
         # Descriptors can all share a single DescriptorSystem.
         # So, bind to the same one as the current descriptor.
-        module_system.descriptor_runtime = descriptor.runtime._descriptor_system
+        module_system.descriptor_runtime = descriptor._runtime  # pylint: disable=protected-access
 
         descriptor.bind_for_student(module_system, descriptor._field_data)
 

common/lib/xmodule/xmodule/tests/test_library_content.py

@@ -54,14 +54,14 @@ class LibraryContentTest(MixedSplitTestCase):
         Bind a module (part of self.course) so we can access student-specific data.
         """
         module_system = get_test_system(course_id=self.course.location.course_key)
-        module_system.descriptor_runtime = module.runtime
+        module_system.descriptor_runtime = module.runtime._descriptor_system  # pylint: disable=protected-access
         module_system._services['library_tools'] = self.tools  # pylint: disable=protected-access
 
         def get_module(descriptor):
             """Mocks module_system get_module function"""
             sub_module_system = get_test_system(course_id=self.course.location.course_key)
             sub_module_system.get_module = get_module
-            sub_module_system.descriptor_runtime = descriptor.runtime
+            sub_module_system.descriptor_runtime = descriptor._runtime  # pylint: disable=protected-access
             descriptor.bind_for_student(sub_module_system, descriptor._field_data)  # pylint: disable=protected-access
             return descriptor
 

common/lib/xmodule/xmodule/tests/test_split_test_module.py

@@ -78,7 +78,7 @@ class SplitTestModuleTest(XModuleXmlImportTest, PartitionTestCase):
         self.course_sequence = self.course.get_children()[0]
         self.module_system = get_test_system()
 
-        self.module_system.descriptor_runtime = self.course.runtime._descriptor_system  # pylint: disable=protected-access
+        self.module_system.descriptor_runtime = self.course._runtime  # pylint: disable=protected-access
         self.course.runtime.export_fs = MemoryFS()
 
         self.partitions_service = StaticPartitionService(

common/lib/xmodule/xmodule/tests/test_vertical.py

@@ -27,7 +27,7 @@ class BaseVerticalModuleTest(XModuleXmlImportTest):
         course_seq = self.course.get_children()[0]
         self.module_system = get_test_system()
 
-        self.module_system.descriptor_runtime = self.course.runtime._descriptor_system  # pylint: disable=protected-access
+        self.module_system.descriptor_runtime = self.course._runtime  # pylint: disable=protected-access
         self.course.runtime.export_fs = MemoryFS()
 
         self.vertical = course_seq.get_children()[0]

common/lib/xmodule/xmodule/x_module.py

@@ -3,6 +3,7 @@ import os
 import sys
 import yaml
 
+from contracts import contract, new_contract
 from functools import partial
 from lxml import etree
 from collections import namedtuple
@@ -1307,6 +1308,9 @@ class DescriptorSystem(MetricsMixin, ConfigurableFragmentWrapper, Runtime):  # p
         pass
 
 
+new_contract('DescriptorSystem', DescriptorSystem)
+
+
 class XMLParsingSystem(DescriptorSystem):
     def __init__(self, process_xml, **kwargs):
         """
@@ -1427,6 +1431,8 @@ class ModuleSystem(MetricsMixin, ConfigurableFragmentWrapper, Runtime):  # pylin
     Note that these functions can be closures over e.g. a django request
     and user, or other environment-specific info.
     """
+
+    @contract(descriptor_runtime='DescriptorSystem')
     def __init__(
             self, static_url, track_function, get_module, render_template,
             replace_urls, descriptor_runtime, user=None, filestore=None,