Issue #25691: Fixed crash on deleting ElementTree.Element attributes.

Lib/test/test_xml_etree.py

@@ -244,6 +244,33 @@ class ElementTreeTest(unittest.TestCase):
         self.assertEqual(ET.XML, ET.fromstring)
         self.assertEqual(ET.PI, ET.ProcessingInstruction)
 
+    def test_set_attribute(self):
+        element = ET.Element('tag')
+
+        self.assertEqual(element.tag, 'tag')
+        element.tag = 'Tag'
+        self.assertEqual(element.tag, 'Tag')
+        element.tag = 'TAG'
+        self.assertEqual(element.tag, 'TAG')
+
+        self.assertIsNone(element.text)
+        element.text = 'Text'
+        self.assertEqual(element.text, 'Text')
+        element.text = 'TEXT'
+        self.assertEqual(element.text, 'TEXT')
+
+        self.assertIsNone(element.tail)
+        element.tail = 'Tail'
+        self.assertEqual(element.tail, 'Tail')
+        element.tail = 'TAIL'
+        self.assertEqual(element.tail, 'TAIL')
+
+        self.assertEqual(element.attrib, {})
+        element.attrib = {'a': 'b', 'c': 'd'}
+        self.assertEqual(element.attrib, {'a': 'b', 'c': 'd'})
+        element.attrib = {'A': 'B', 'C': 'D'}
+        self.assertEqual(element.attrib, {'A': 'B', 'C': 'D'})
+
     def test_simpleops(self):
         # Basic method sanity checks.
 

Lib/test/test_xml_etree_c.py

@@ -22,6 +22,38 @@ class MiscTests(unittest.TestCase):
         finally:
             data = None
 
+    def test_del_attribute(self):
+        element = cET.Element('tag')
+
+        element.tag = 'TAG'
+        with self.assertRaises(AttributeError):
+            del element.tag
+        self.assertEqual(element.tag, 'TAG')
+
+        with self.assertRaises(AttributeError):
+            del element.text
+        self.assertIsNone(element.text)
+        element.text = 'TEXT'
+        with self.assertRaises(AttributeError):
+            del element.text
+        self.assertEqual(element.text, 'TEXT')
+
+        with self.assertRaises(AttributeError):
+            del element.tail
+        self.assertIsNone(element.tail)
+        element.tail = 'TAIL'
+        with self.assertRaises(AttributeError):
+            del element.tail
+        self.assertEqual(element.tail, 'TAIL')
+
+        with self.assertRaises(AttributeError):
+            del element.attrib
+        self.assertEqual(element.attrib, {})
+        element.attrib = {'A': 'B', 'C': 'D'}
+        with self.assertRaises(AttributeError):
+            del element.attrib
+        self.assertEqual(element.attrib, {'A': 'B', 'C': 'D'})
+
 
 @unittest.skipUnless(cET, 'requires _elementtree')
 class TestAliasWorking(unittest.TestCase):

Misc/NEWS

@@ -77,6 +77,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #25691: Fixed crash on deleting ElementTree.Element attributes.
+
 - Issue #25624: ZipFile now always writes a ZIP_STORED header for directory
   entries.  Patch by Dingyuan Wang.
 

Modules/_elementtree.c

@@ -1921,6 +1921,12 @@ static int
 element_setattro(ElementObject* self, PyObject* nameobj, PyObject* value)
 {
     char *name = "";
+
+    if (value == NULL) {
+        PyErr_SetString(PyExc_AttributeError,
+            "can't delete attribute");
+        return -1;
+    }
     if (PyUnicode_Check(nameobj))
         name = _PyUnicode_AsString(nameobj);
     if (name == NULL)