Clear cached children when binding an XModuleDescriptor/XBlock to a particular user

lms/djangoapps/courseware/module_render.py

@@ -497,10 +497,8 @@ def get_module_system_for_user(user, field_data_cache,
         # rebinds module to a different student.  We'll change system, student_data, and scope_ids
         module.descriptor.bind_for_student(
             inner_system,
-            LmsFieldData(module.descriptor._field_data, inner_student_data)  # pylint: disable=protected-access
-        )
-        module.descriptor.scope_ids = (
-            module.descriptor.scope_ids._replace(user_id=real_user.id)  # pylint: disable=protected-access
+            LmsFieldData(module.descriptor._field_data, inner_student_data),  # pylint: disable=protected-access
+            real_user.id,
         )
         module.scope_ids = module.descriptor.scope_ids  # this is needed b/c NamedTuples are immutable
         # now bind the module to the new ModuleSystem instance and vice-versa
@@ -688,8 +686,7 @@ def get_module_for_descriptor_internal(user, descriptor, field_data_cache, cours
         request_token=request_token
     )
 
-    descriptor.bind_for_student(system, field_data)  # pylint: disable=protected-access
-    descriptor.scope_ids = descriptor.scope_ids._replace(user_id=user.id)  # pylint: disable=protected-access
+    descriptor.bind_for_student(system, field_data, user.id)  # pylint: disable=protected-access
     return descriptor
 
 

lms/djangoapps/courseware/tests/test_module_render.py

@@ -921,7 +921,7 @@ class TestAnonymousStudentId(ModuleStoreTestCase, LoginEnrollmentTestCase):
         location = course_id.make_usage_key('dummy_category', 'dummy_name')
         descriptor = Mock(
             spec=xblock_class,
-            _field_data=Mock(spec=FieldData),
+            _field_data=Mock(spec=FieldData, name='field_data'),
             location=location,
             static_asset_path=None,
             _runtime=Mock(
@@ -931,7 +931,10 @@ class TestAnonymousStudentId(ModuleStoreTestCase, LoginEnrollmentTestCase):
                 name='runtime',
             ),
             scope_ids=Mock(spec=ScopeIds),
-            name='descriptor'
+            name='descriptor',
+            _field_data_cache={},
+            _dirty_fields={},
+            fields={},
         )
         descriptor.runtime = CombinedSystem(descriptor._runtime, None)  # pylint: disable=protected-access
         # Use the xblock_class's bind_for_student method