gh-155742: Remove dead code in _elementtree

Lib/test/test_xml_etree.py

@@ -3336,6 +3336,51 @@ def __iter__(self):
         e.extend([ET.Element(f'c{i}') for i in range(10)])
         e[:] = V()
 
+    def test_treebuilder_data(self):
+        # single data() call: pass the string object
+        b = ET.TreeBuilder()
+        b.start('root', {})
+        b.data('ABCD')
+        b.end('root')
+        elem = b.close()
+        self.assertEqual(elem.text, 'ABCD')
+
+        # two data() calls: join the two strings
+        b = ET.TreeBuilder()
+        b.start('root', {})
+        b.data('ABCD')
+        b.data('EFGH')
+        b.end('root')
+        elem = b.close()
+        self.assertEqual(elem.text, 'ABCDEFGH')
+
+    def test_treebuilder_data_wrong_types(self):
+        for obj in (b'bytes', 123, 1.0):
+            # single data() call
+            try:
+                b = ET.TreeBuilder()
+                b.start('tag', {})
+                b.data(obj)
+                b.end('tag')
+            except TypeError:
+                # Python implementation raises TypeError,
+                # C implementation doesn't.
+                pass
+            else:
+                elem = b.close()
+                self.assertEqual(elem.text, obj)
+
+            # two data() calls
+            errmsg = f'expected str instance, {type(obj).__name__} found'
+            with self.assertRaisesRegex(TypeError, errmsg):
+                b = ET.TreeBuilder()
+                b.start('tag', {})
+                b.data(obj)
+                b.data(obj)
+                b.end('tag')
+                elem = b.close()
+                _ = elem.text
+
     def test_treebuilder_start(self):
         # Issue #27863
         def element_factory(x, y):

Modules/_elementtree.c

@@ -2935,17 +2935,7 @@ treebuilder_handle_data(TreeBuilderObject* self, PyObject* data)
         self->data = Py_NewRef(data);
     } else {
         /* more than one item; use a list to collect items */
-        if (PyBytes_CheckExact(self->data)
-            && _PyObject_IsUniquelyReferenced(self->data)
-            && PyBytes_CheckExact(data) && PyBytes_GET_SIZE(data) == 1) {
-            /* XXX this code path unused in Python 3? */
-            /* expat often generates single character data sections; handle
-               the most common case by resizing the existing string... */
-            Py_ssize_t size = PyBytes_GET_SIZE(self->data);
-            if (_PyBytes_Resize(&self->data, size + 1) < 0)
-                return NULL;
-            PyBytes_AS_STRING(self->data)[size] = PyBytes_AS_STRING(data)[0];
-        } else if (PyList_CheckExact(self->data)) {
+        if (PyList_CheckExact(self->data)) {
             if (PyList_Append(self->data, data) < 0)
                 return NULL;
         } else {