use a universal null handler

common/lib/xmodule/xmodule/modulestore/__init__.py

@@ -154,17 +154,6 @@ class ActiveBulkThread(threading.local):
         self.records = defaultdict(bulk_ops_record_type)
 
 
-class NullSignalHandler(object):
-    """
-    A null handler that does nothing
-    """
-    def send(self, *args, **kwargs):
-        """
-        No-op
-        """
-        pass
-
-
 class BulkOperationsMixin(object):
     """
     This implements the :meth:`bulk_operations` modulestore semantics which handles nested invocations
@@ -180,23 +169,6 @@ class BulkOperationsMixin(object):
     def __init__(self, *args, **kwargs):
         super(BulkOperationsMixin, self).__init__(*args, **kwargs)
         self._active_bulk_ops = ActiveBulkThread(self._bulk_ops_record_type)
-        self._signal_handler = None
-
-    @property
-    def signal_handler(self):
-        """
-        Return a signal handler, defaults to a null handler that does nothing.
-        """
-        if not self._signal_handler:
-            self._signal_handler = NullSignalHandler()
-        return self._signal_handler
-
-    @signal_handler.setter
-    def signal_handler(self, value):
-        """
-        Set the signal handler
-        """
-        self._signal_handler = value
 
     @contextmanager
     def bulk_operations(self, course_id, emit_signals=True):

common/lib/xmodule/xmodule/modulestore/django.py

@@ -26,6 +26,7 @@ from xmodule.contentstore.django import contentstore
 from xmodule.modulestore.draft_and_published import BranchSettingMixin
 from xmodule.modulestore.mixed import MixedModuleStore
 from xmodule.util.django import get_current_request_hostname
+from xmodule.util.null_handler import NullHandler
 import xblock.reference.plugins
 
 
@@ -129,7 +130,7 @@ def create_modulestore_instance(
         i18n_service=None,
         fs_service=None,
         user_service=None,
-        signal_handler=None,
+        signal_handler=NullHandler(),
 ):
     """
     This will return a new instance of a modulestore given an engine and options

common/lib/xmodule/xmodule/modulestore/mixed.py

@@ -16,6 +16,7 @@ from opaque_keys.edx.keys import CourseKey, AssetKey
 from opaque_keys.edx.locator import LibraryLocator
 from opaque_keys.edx.locations import SlashSeparatedCourseKey
 from xmodule.assetstore import AssetMetadata
+from xmodule.util.null_handler import NullHandler
 
 from . import ModuleStoreWriteBase
 from . import ModuleStoreEnum
@@ -108,7 +109,7 @@ class MixedModuleStore(ModuleStoreDraftAndPublished, ModuleStoreWriteBase):
             fs_service=None,
             user_service=None,
             create_modulestore_instance=None,
-            signal_handler=None,
+            signal_handler=NullHandler(),
             **kwargs
     ):
         """

common/lib/xmodule/xmodule/modulestore/mongo/base.py

@@ -50,6 +50,7 @@ from xmodule.modulestore.exceptions import ItemNotFoundError, DuplicateCourseErr
 from xmodule.modulestore.inheritance import InheritanceMixin, inherit_metadata, InheritanceKeyValueStore
 from xmodule.modulestore.xml import CourseLocationManager
 from xmodule.services import SettingsService
+from xmodule.util.null_handler import NullHandler
 
 log = logging.getLogger(__name__)
 
@@ -543,7 +544,7 @@ class MongoModuleStore(ModuleStoreDraftAndPublished, ModuleStoreWriteBase, Mongo
                  i18n_service=None,
                  fs_service=None,
                  user_service=None,
-                 signal_handler=None,
+                 signal_handler=NullHandler(),
                  retry_wait_time=0.1,
                  **kwargs):
         """

common/lib/xmodule/xmodule/modulestore/split_mongo/split.py

@@ -67,6 +67,7 @@ from bson.objectid import ObjectId
 from xblock.core import XBlock
 from xblock.fields import Scope, Reference, ReferenceList, ReferenceValueDict
 from xmodule.errortracker import null_error_tracker
+from xmodule.util.null_handler import NullHandler
 from opaque_keys.edx.locator import (
     BlockUsageLocator, DefinitionLocator, CourseLocator, LibraryLocator, VersionTree, LocalId,
 )
@@ -640,7 +641,7 @@ class SplitMongoModuleStore(SplitBulkWriteMixin, ModuleStoreWriteBase):
                  default_class=None,
                  error_tracker=null_error_tracker,
                  i18n_service=None, fs_service=None, user_service=None,
-                 services=None, signal_handler=None, **kwargs):
+                 services=None, signal_handler=NullHandler(), **kwargs):
         """
         :param doc_store_config: must have a host, db, and collection entries. Other common entries: port, tz_aware.
         """

common/lib/xmodule/xmodule/modulestore/tests/utils.py

@@ -6,6 +6,7 @@ from opaque_keys.edx.keys import UsageKey
 from unittest import TestCase
 from xblock.fields import XBlockMixin
 from xmodule.x_module import XModuleMixin
+from xmodule.util.null_handler import NullHandler
 from xmodule.modulestore import ModuleStoreEnum
 from xmodule.modulestore.draft_and_published import ModuleStoreDraftAndPublished
 from xmodule.modulestore.edit_info import EditInfoMixin
@@ -36,7 +37,7 @@ def create_modulestore_instance(
         i18n_service=None,
         fs_service=None,
         user_service=None,
-        signal_handler=None,
+        signal_handler=NullHandler(),
 ):
     """
     This will return a new instance of a modulestore given an engine and options

common/lib/xmodule/xmodule/modulestore/xml.py

@@ -26,6 +26,7 @@ from xmodule.x_module import (
 from xmodule.modulestore.xml_exporter import DEFAULT_CONTENT_FIELDS
 from xmodule.modulestore import ModuleStoreEnum, ModuleStoreReadBase, LIBRARY_ROOT, COURSE_ROOT
 from xmodule.tabs import CourseTabList
+from xmodule.util.null_handler import NullHandler
 from opaque_keys.edx.locations import SlashSeparatedCourseKey, Location
 from opaque_keys.edx.locator import CourseLocator, LibraryLocator
 
@@ -335,7 +336,7 @@ class XMLModuleStore(ModuleStoreReadBase):
     def __init__(
             self, data_dir, default_class=None, source_dirs=None, course_ids=None,
             load_error_modules=True, i18n_service=None, fs_service=None, user_service=None,
-            signal_handler=None, target_course_id=None, **kwargs   # pylint: disable=unused-argument
+            signal_handler=NullHandler(), target_course_id=None, **kwargs   # pylint: disable=unused-argument
     ):
         """
         Initialize an XMLModuleStore from data_dir

common/lib/xmodule/xmodule/util/null_handler.py

+class NullHandler(object):
+    """
+    Responds to an any method call.
+    """
+    def __getattr__(self, name):
+        def method(*args, **kwargs):
+            pass
+        return method
+