From 7176cfc9abbd53a99694645d2b7a627fe25d3be3 Mon Sep 17 00:00:00 2001
From: Sebastian Wozniak <sebastian.wozniak@empsgroup.com>
Date: Wed, 26 Nov 2025 13:16:30 +0100
Subject: [PATCH] fix: preserve attribute values when extending complexType

When a complexType with only attributes was extended by another
complexType, the attributes were being rendered as "NotSet" instead
of their actual values. This occurred because a placeholder element
was unnecessarily created during type extension, causing the base type
to be rendered twice - once with correct values and once with empty
values that overwrote the correct ones.

Fixes #991
---
 src/zeep/xsd/types/complex.py   |   2 +
 tests/test_xsd_complex_types.py | 104 ++++++++++++++++++++++++++++++++
 2 files changed, 106 insertions(+)

diff --git a/src/zeep/xsd/types/complex.py b/src/zeep/xsd/types/complex.py
index 4c69a9cde..65c39b953 100644
--- a/src/zeep/xsd/types/complex.py
+++ b/src/zeep/xsd/types/complex.py
@@ -447,6 +447,8 @@ def extend(self, base):
 
         elif self._element or base_element:
             element = self._element or base_element
+        elif isinstance(base, ComplexType):
+            element = None
         else:
             element = Element("_value_1", base)
 
diff --git a/tests/test_xsd_complex_types.py b/tests/test_xsd_complex_types.py
index 55430c91f..6efb8945b 100644
--- a/tests/test_xsd_complex_types.py
+++ b/tests/test_xsd_complex_types.py
@@ -422,3 +422,107 @@ def test_ignore_sequence_order():
 
     response = elm.parse(node[0], schema)
     assert response.Baz.id == 3
+
+
+def test_extension_with_attributes_preserves_values():
+    schema = xsd.Schema(
+        load_xml(
+            """
+        <?xml version="1.0"?>
+        <schema xmlns="http://www.w3.org/2001/XMLSchema"
+                xmlns:tns="http://tests.python-zeep.org/"
+                targetNamespace="http://tests.python-zeep.org/"
+                elementFormDefault="unqualified"
+                attributeFormDefault="unqualified">
+          <complexType name="BaseType">
+            <attribute name="attr1" type="integer" use="required"/>
+            <attribute name="attr2" type="string" use="required"/>
+          </complexType>
+          <complexType name="ExtendedType">
+            <complexContent>
+              <extension base="tns:BaseType"/>
+            </complexContent>
+          </complexType>
+          <element name="item" type="tns:ExtendedType"/>
+        </schema>
+    """
+        )
+    )
+    schema.set_ns_prefix("tns", "http://tests.python-zeep.org/")
+
+    item_elm = schema.get_element("tns:item")
+    obj = item_elm(attr1=10, attr2="test")
+
+    assert obj.attr1 == 10
+    assert obj.attr2 == "test"
+
+    result = render_node(item_elm, obj)
+    expected = """
+      <document>
+        <ns0:item xmlns:ns0="http://tests.python-zeep.org/" attr1="10" attr2="test"/>
+      </document>
+    """
+    assert_nodes_equal(result, expected)
+
+    parsed = item_elm.parse(result[0], schema)
+    assert parsed.attr1 == 10
+    assert parsed.attr2 == "test"
+
+
+def test_extension_with_attributes_and_elements():
+    schema = xsd.Schema(
+        load_xml(
+            """
+        <?xml version="1.0"?>
+        <schema xmlns="http://www.w3.org/2001/XMLSchema"
+                xmlns:tns="http://tests.python-zeep.org/"
+                targetNamespace="http://tests.python-zeep.org/"
+                elementFormDefault="unqualified"
+                attributeFormDefault="unqualified">
+          <complexType name="BaseType">
+            <attribute name="attr1" type="integer" use="required"/>
+            <attribute name="attr2" type="string" use="required"/>
+          </complexType>
+          <complexType name="ContainerBaseType" abstract="true">
+            <sequence>
+              <element name="item" type="tns:ExtendedType"/>
+            </sequence>
+          </complexType>
+          <complexType name="ExtendedType">
+            <complexContent>
+              <extension base="tns:BaseType"/>
+            </complexContent>
+          </complexType>
+          <complexType name="ContainerType">
+            <complexContent>
+              <extension base="tns:ContainerBaseType"/>
+            </complexContent>
+          </complexType>
+          <element name="container" type="tns:ContainerType"/>
+        </schema>
+    """
+        )
+    )
+    schema.set_ns_prefix("tns", "http://tests.python-zeep.org/")
+
+    container_elm = schema.get_element("tns:container")
+    extended_type = schema.get_type("tns:ExtendedType")
+
+    obj = container_elm(item=extended_type(attr1=10, attr2="test"))
+
+    assert obj.item.attr1 == 10
+    assert obj.item.attr2 == "test"
+
+    result = render_node(container_elm, obj)
+    expected = """
+      <document>
+        <ns0:container xmlns:ns0="http://tests.python-zeep.org/">
+          <item attr1="10" attr2="test"/>
+        </ns0:container>
+      </document>
+    """
+    assert_nodes_equal(result, expected)
+
+    parsed = container_elm.parse(result[0], schema)
+    assert parsed.item.attr1 == 10
+    assert parsed.item.attr2 == "test"