fix: withdrawn by author

xmodule/modulestore/tests/test_xml.py

@@ -159,3 +159,71 @@ def test_tilde_files_ignored(self, _fake_glob):  # noqa: PT019
         about_block = modulestore.get_item(about_location)
         assert 'GREEN' in about_block.data
         assert 'RED' not in about_block.data
+
+
+class TestLoadPointerNodeHelper(TestCase):
+    """
+    Unit tests for ``XMLParsingModuleStoreRuntime._load_pointer_node``.
+
+    Regression for bug #36390: external XBlocks (which do not inherit
+    ``XmlMixin``) must be able to import pointer-tag OLX like built-in
+    blocks. The runtime-level helper is the new chokepoint.
+    """
+
+    def _make_runtime_with_fs(self, fs):
+        """Instantiate just the helper without building a full modulestore."""
+        from xmodule.modulestore.xml import XMLParsingModuleStoreRuntime
+        runtime = XMLParsingModuleStoreRuntime.__new__(XMLParsingModuleStoreRuntime)
+        runtime.resources_fs = fs
+        return runtime
+
+    def test_unit_load_pointer_node_reads_referenced_file(self):
+        """Pointer node resolves by reading ``<tag>/<url_name>.xml``."""
+        from fs.memoryfs import MemoryFS
+        from lxml import etree as _etree
+
+        fs = MemoryFS()
+        fs.makedirs("ext_block")
+        with fs.open("ext_block/hello.xml", "w") as fp:
+            fp.write('<ext_block url_name="hello">PAYLOAD</ext_block>')
+
+        runtime = self._make_runtime_with_fs(fs)
+        pointer = _etree.fromstring('<ext_block url_name="hello"/>')
+        resolved = runtime._load_pointer_node(pointer)  # pylint: disable=protected-access
+        assert resolved.tag == "ext_block"
+        assert (resolved.text or "").strip() == "PAYLOAD"
+        assert resolved.get("url_name") == "hello"
+
+    def test_unit_load_pointer_node_preserves_url_name_if_missing(self):
+        """When the inner file omits url_name, we copy it from the pointer."""
+        from fs.memoryfs import MemoryFS
+        from lxml import etree as _etree
+
+        fs = MemoryFS()
+        fs.makedirs("ext_block")
+        with fs.open("ext_block/foo.xml", "w") as fp:
+            fp.write('<ext_block>BODY</ext_block>')
+
+        runtime = self._make_runtime_with_fs(fs)
+        pointer = _etree.fromstring('<ext_block url_name="foo"/>')
+        resolved = runtime._load_pointer_node(pointer)  # pylint: disable=protected-access
+        assert resolved.get("url_name") == "foo"
+
+    def test_bug_36390_regression_load_pointer_node_honors_url_name(self):
+        """
+        Regression for bug #36390: an inner file that already declares
+        ``url_name`` must not be clobbered by the pointer's url_name.
+        """
+        from fs.memoryfs import MemoryFS
+        from lxml import etree as _etree
+
+        fs = MemoryFS()
+        fs.makedirs("ext_block")
+        with fs.open("ext_block/bar.xml", "w") as fp:
+            fp.write('<ext_block url_name="inner-name">BODY</ext_block>')
+
+        runtime = self._make_runtime_with_fs(fs)
+        pointer = _etree.fromstring('<ext_block url_name="bar"/>')
+        resolved = runtime._load_pointer_node(pointer)  # pylint: disable=protected-access
+        # The inner file's url_name wins (it was explicitly set).
+        assert resolved.get("url_name") == "inner-name"

xmodule/modulestore/xml.py

@@ -92,6 +92,15 @@ def xblock_from_node(self, node, parent_id, id_generator=None):
         keys = ScopeIds(None, block_type, def_id, usage_id)
         block_class = self.mixologist.mix(self.load_block_type(block_type))
 
+        # Resolve pointer-tag syntax at the runtime level so external XBlocks
+        # (which do not inherit XmlMixin) can be loaded from a separate file
+        # just like built-in blocks. Classes that already inherit XmlMixin
+        # handle pointer tags in their own parse_xml, so we skip to avoid a
+        # double file read. See bug #36390.
+        from xmodule.xml_block import XmlMixin, is_pointer_tag  # noqa: PLC0415
+        if is_pointer_tag(node) and not issubclass(block_class, XmlMixin):
+            node = self._load_pointer_node(node)
+
         aside_children = self.parse_asides(node, def_id, usage_id, id_generator)
         asides_tags = [x.tag for x in aside_children]
 
@@ -107,6 +116,27 @@ def xblock_from_node(self, node, parent_id, id_generator=None):
 
         return block
 
+    def _load_pointer_node(self, node):
+        """
+        Resolve a pointer-tag XML node (e.g. ``<drag-and-drop-v2 url_name="foo"/>``)
+        by loading the referenced file from ``resources_fs``. Returns the
+        resolved ``lxml.etree`` element.
+
+        Used so external XBlocks — which do not inherit ``XmlMixin`` — can be
+        imported from pointer-tag OLX at the runtime level. See bug #36390.
+        """
+        from lxml import etree as _etree  # noqa: PLC0415
+        from xmodule.xml_block import EDX_XML_PARSER, name_to_pathname  # noqa: PLC0415
+
+        url_name = node.get("url_name")
+        filepath = f"{node.tag}/{name_to_pathname(url_name)}.xml"
+        with self.resources_fs.open(filepath) as xml_file:
+            resolved = _etree.parse(xml_file, parser=EDX_XML_PARSER).getroot()
+        # Preserve the url_name from the pointer tag — inner files may omit it.
+        if "url_name" not in resolved.attrib:
+            resolved.set("url_name", url_name)
+        return resolved
+
     def parse_asides(self, node, def_id, usage_id, id_generator):
         """pull the asides out of the xml payload and instantiate them"""
         aside_children = []

xmodule/x_module.py

@@ -1550,10 +1550,33 @@ def resource_url(self, resource):
         raise NotImplementedError("edX Platform doesn't currently implement XBlock resource urls")
 
     def add_block_as_child_node(self, block, node):
-        """Append the block’s XML to the given parent XML node."""
+        """Append the block's XML to the given parent XML node.
+
+        For blocks that do not inherit ``XmlMixin`` (i.e. external XBlocks),
+        also write the block's definition to a separate file and leave a
+        pointer tag in the parent, matching the export format used by
+        built-in blocks. See bug #36390.
+        """
+        from xmodule.xml_block import XmlMixin, name_to_pathname  # noqa: PLC0415
         child = etree.SubElement(node, block.category)
         child.set("url_name", block.url_name)
-        block.add_xml_to_node(child)
+        if not isinstance(block, XmlMixin) and hasattr(self, "export_fs"):
+            # External block: dispatch into a scratch element, then serialize
+            # that element into its own file, leaving only a pointer tag here.
+            scratch = etree.Element(block.category)
+            block.add_xml_to_node(scratch)
+            url_path = name_to_pathname(block.url_name)
+            filepath = f"{block.category}/{url_path}.xml"
+            dirname = os.path.dirname(filepath)
+            if dirname:
+                self.export_fs.makedirs(dirname, recreate=True)
+            with self.export_fs.open(filepath, "wb") as fileobj:
+                etree.ElementTree(scratch).write(
+                    fileobj, pretty_print=True, encoding="utf-8",
+                )
+            # Leave the child node as a pure pointer; url_name is already set.
+        else:
+            block.add_xml_to_node(child)
 
     def publish(self, block, event_type, event_data):
         """