[3.12] gh-119577: Adjust DeprecationWarning when testing element truth values in Element tree (GH-119762) (#120190)

gh-119577: Adjust DeprecationWarning when testing element truth values in ElementTree (GH-119762)

Adjust DeprecationWarning when testing element truth values in
ElementTree, we're planning to go with the more natural True return
rather than a disruptive harder to code around exception raise, and are
deferring the behavior change for a few more releases.

Co-authored-by: Jacob Walls <[email protected]>

Author: gpshead

Doc/library/xml.etree.elementtree.rst

@@ -1054,9 +1054,10 @@ Element Objects
    :meth:`~object.__getitem__`, :meth:`~object.__setitem__`,
    :meth:`~object.__len__`.
 
-   Caution: Elements with no subelements will test as ``False``.  Testing the
-   truth value of an Element is deprecated and will raise an exception in
-   Python 3.14.  Use specific ``len(elem)`` or ``elem is None`` test instead.::
+   Caution: Elements with no subelements will test as ``False``.  In a future
+   release of Python, all elements will test as ``True`` regardless of whether
+   subelements exist.  Instead, prefer explicit ``len(elem)`` or
+   ``elem is not None`` tests.::
 
      element = root.find('foo')
 

Lib/test/test_xml_etree.py

@@ -4009,7 +4009,7 @@ class BoolTest(unittest.TestCase):
     def test_warning(self):
         e = ET.fromstring('<a style="new"></a>')
         msg = (
-            r"Testing an element's truth value will raise an exception in "
+            r"Testing an element's truth value will always return True in "
             r"future versions.  "
             r"Use specific 'len\(elem\)' or 'elem is not None' test instead.")
         with self.assertWarnsRegex(DeprecationWarning, msg):

Lib/xml/etree/ElementTree.py

@@ -201,7 +201,7 @@ def __len__(self):
 
     def __bool__(self):
         warnings.warn(
-            "Testing an element's truth value will raise an exception in "
+            "Testing an element's truth value will always return True in "
             "future versions.  "
             "Use specific 'len(elem)' or 'elem is not None' test instead.",
             DeprecationWarning, stacklevel=2

Misc/NEWS.d/next/Library/2024-05-29-21-50-05.gh-issue-119577.S3BlKJ.rst

@@ -0,0 +1,4 @@
+The :exc:`DeprecationWarning` emitted when testing the truth value of an
+:class:`xml.etree.ElementTree.Element` now describes unconditionally
+returning ``True`` in a future version rather than raising an exception in
+Python 3.14.

Modules/_elementtree.c

@@ -1504,7 +1504,7 @@ element_bool(PyObject* self_)
 {
     ElementObject* self = (ElementObject*) self_;
     if (PyErr_WarnEx(PyExc_DeprecationWarning,
-                     "Testing an element's truth value will raise an exception "
+                     "Testing an element's truth value will always return True "
                      "in future versions.  Use specific 'len(elem)' or "
                      "'elem is not None' test instead.",
                      1) < 0) {