In Python 3.12 xml.etree.ElementTree will raise DeprecationWarning: Testing an element's truth value will raise an exception in future versions

[matthewfeickert]

While testing Python 3.12 in CI

pyhf/tests/test_export.py

Lines 438 to 450 in adddb07

	def test_integer_data(datadir, mocker):
	"""
	Test that a spec with only integer data will be written correctly
	"""
	with open(
	datadir.joinpath("workspace_integer_data.json"), encoding="utf-8"
	) as spec_file:
	spec = json.load(spec_file)
	channel_spec = spec["channels"][0]
	mocker.patch("pyhf.writexml._ROOT_DATA_FILE")
	channel = pyhf.writexml.build_channel(spec, channel_spec, {})
	assert channel

raised

>       assert channel
E       DeprecationWarning: Testing an element's truth value will raise an exception in future versions.  Use specific 'len(elem)' or 'elem is not None' test instead.

This comes from python/cpython#83122 which landed in Python 3.12. This should get fixed before Python 3.12 support is added.

From the Python 3.12 docs: https://docs.python.org/3.12/library/xml.etree.elementtree.html#element-objects

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.:

element = root.find('foo')

if not element:  # careful!
    print("element not found, or element has no subelements")

if element is None:
    print("element not found")

Changed in version 3.12: Testing the truth value of an Element emits DeprecationWarning.