refactor: delete class XmlDescriptor

It also adds `@XBlock.needs("i18n")` to `XModuleMixin` because this service is
required there.

cms/djangoapps/contentstore/course_info_model.py

@@ -24,7 +24,7 @@ from xmodule.html_module import CourseInfoBlock  # lint-amnesty, pylint: disable
 from xmodule.modulestore.django import modulestore  # lint-amnesty, pylint: disable=wrong-import-order
 from xmodule.modulestore.exceptions import ItemNotFoundError  # lint-amnesty, pylint: disable=wrong-import-order
 
-# # This should be in a class which inherits from XmlDescriptor
+# # This should be in a class which inherits from XModuleDescriptor
 log = logging.getLogger(__name__)
 
 

xmodule/raw_module.py

@@ -4,7 +4,6 @@ import re
 
 from lxml import etree
 from xblock.fields import Scope, String
-from xmodule.xml_module import XmlDescriptor  # pylint: disable=unused-import
 
 from .exceptions import SerializationError
 

xmodule/tests/test_xml_module.py

@@ -20,7 +20,7 @@ from xmodule.tests import get_test_descriptor_system
 from xmodule.tests.xml import XModuleXmlImportTest
 from xmodule.tests.xml.factories import CourseFactory, ProblemFactory, SequenceFactory
 from xmodule.x_module import XModuleMixin
-from xmodule.xml_module import XmlDescriptor, deserialize_field, serialize_field
+from xmodule.xml_module import XmlMixin, deserialize_field, serialize_field
 
 
 class CrazyJsonString(String):
@@ -65,7 +65,7 @@ class InheritingFieldDataTest(unittest.TestCase):
     Tests of InheritingFieldData.
     """
 
-    class TestableInheritingXBlock(XmlDescriptor):  # lint-amnesty, pylint: disable=abstract-method
+    class TestableInheritingXBlock(XmlMixin):  # lint-amnesty, pylint: disable=abstract-method
         """
         An XBlock we can use in these tests.
         """
@@ -227,11 +227,15 @@ class InheritingFieldDataTest(unittest.TestCase):
 
 
 class EditableMetadataFieldsTest(unittest.TestCase):
+    class TestableXmlXBlock(XmlMixin, XModuleMixin):  # lint-amnesty, pylint: disable=abstract-method
+        """
+        This is subclassing `XModuleMixin` to use metadata fields in the unmixed class.
+        """
 
     def test_display_name_field(self):
         editable_fields = self.get_xml_editable_fields(DictFieldData({}))
         # Tests that the xblock fields (currently tags and name) get filtered out.
-        # Also tests that xml_attributes is filtered out of XmlDescriptor.
+        # Also tests that xml_attributes is filtered out of XmlMixin.
         assert 1 == len(editable_fields), editable_fields
         self.assert_field_values(
             editable_fields, 'display_name', XModuleMixin.display_name,
@@ -334,13 +338,13 @@ class EditableMetadataFieldsTest(unittest.TestCase):
     def get_xml_editable_fields(self, field_data):
         runtime = get_test_descriptor_system()
         return runtime.construct_xblock_from_class(
-            XmlDescriptor,
+            self.TestableXmlXBlock,
             scope_ids=Mock(),
             field_data=field_data,
         ).editable_metadata_fields
 
     def get_descriptor(self, field_data):
-        class TestModuleDescriptor(TestFields, XmlDescriptor):  # lint-amnesty, pylint: disable=abstract-method
+        class TestModuleDescriptor(TestFields, self.TestableXmlXBlock):  # lint-amnesty, pylint: disable=abstract-method
             @property
             def non_editable_metadata_fields(self):
                 non_editable_fields = super().non_editable_metadata_fields

xmodule/x_module.py

@@ -279,6 +279,7 @@ class XModuleFields:
     )
 
 
+@XBlock.needs("i18n")
 class XModuleMixin(XModuleFields, XBlock):
     """
     Fields and methods used by XModules internally.

xmodule/xml_module.py

@@ -8,14 +8,12 @@ import os
 
 from lxml import etree
 from lxml.etree import ElementTree, XMLParser
-from xblock.core import XBlock, XML_NAMESPACES
+from xblock.core import XML_NAMESPACES
 from xblock.fields import Dict, Scope, ScopeIds
 from xblock.runtime import KvsFieldData
 from xmodule.modulestore import EdxJSONEncoder
 from xmodule.modulestore.inheritance import InheritanceKeyValueStore, own_metadata
 
-from .x_module import XModuleMixin
-
 log = logging.getLogger(__name__)
 
 # assume all XML files are persisted as utf-8.
@@ -505,8 +503,3 @@ class XmlMixin:
         non_editable_fields = super().non_editable_metadata_fields
         non_editable_fields.append(XmlMixin.xml_attributes)
         return non_editable_fields
-
-
-@XBlock.needs("i18n")
-class XmlDescriptor(XmlMixin, XModuleMixin):  # lint-amnesty, pylint: disable=abstract-method
-    pass