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Adjust deprecation warning re: testing truth value of xml.etree.ElementTree.Element #119577
Description
Testing the truth value of an ElementTree.Element was deprecated in python 3.12 and scheduled for removal in 3.14. I have a patch ready.
- xml.etree.ElementTree.Element inconsistent warning for bool #83122
- gh-83122: Deprecate testing element truth values in ElementTree #31149
Linked PRs
- gh-119577: Raise RuntimeError when testing element truth values in ElementTree #119578
- gh-119577: Adjust DeprecationWarning when testing element truth values in ElementTree #119762
- [3.13] gh-119577: Adjust DeprecationWarning when testing element truth values in ElementTree (GH-119762) #120189
- [3.12] gh-119577: Adjust DeprecationWarning when testing element truth values in Element tree (GH-119762) #120190
Activity
pythongh-119577: Raise RuntimeError when testing element truth values…
pythongh-119577: Raise RuntimeError when testing element truth values…
serhiy-storchaka commented on May 27, 2024
AFAIK, the plan was to return True instead of raising an exception.
jacobtylerwalls commented on May 28, 2024
In favor of raising an error: #83122 (comment)
In favor of DeprecationWarning being the choice for an exception vs. FutureWarning being the choice to for a behavior change: #83122 (comment)
cc/ @gpshead who reviewed #31149, which changed FutureWarning to DeprecationWarning and documented that an exception would be raised.
serhiy-storchaka commented on May 28, 2024
Raising an exception in __bool__() is extremely uncommon behavior. For now, there is only one special case -- NotImplemented, and it is a very special case. On other hand, there is a precedence of datetime.time -- the midnight had the false boolean value, and now it has lost its special meaning and has the same boolean value like all other datetime.time values.
gpshead commented on May 28, 2024
We did document that it would raise an exception in the future. But I agree that that is unusual.
Lets be conservative and delay the __bool__ behavior change on Element for a few more releases until the 3.16 timeframe to let the DeprecationWarning be more widely seen and acted upon in existing code. In 3.16+ we can (edit updated:) make its __bool__ method return true. Thus making all instances truthy as most class instances are.
What that means is that we need a PR to update the docs and the DeprecationWarning error message to reflect the new plan.
bool raising an exception does have valid uses: Such as when a class that is commonly mistaken for an actual boolean value in some API designs is easily misused in the wrong context. Element doesn't seem like one of those.
serhiy-storchaka commented on May 28, 2024
We cannot just remove __bool__. Element has __len__, and this is the reason why childless elements had the false boolean value, why this deprecation started. It should be a method that always returns True. Yes, inconsistency between __len__ and __bool__ is also unusual, but this considered lesser evil than having the false boolean value for otherwise normal elements.
pythongh-119577: Adjust DeprecationWarning when testing element truth…
pythongh-119577: Adjust DeprecationWarning when testing element truth…
jacobtylerwalls commented on Jun 6, 2024
New PR: #119762
gh-119577: Adjust DeprecationWarning when testing element truth value…
pythongh-119577: Adjust DeprecationWarning when testing element truth…
pythongh-119577: Adjust DeprecationWarning when testing element truth…
[3.13] gh-119577: Adjust DeprecationWarning when testing element trut…
pythongh-119577: Adjust DeprecationWarning when testing element truth…
pythongh-119577: Adjust DeprecationWarning when testing element truth…
pythongh-119577: Adjust DeprecationWarning when testing element truth…
[3.12] gh-119577: Adjust DeprecationWarning when testing element trut…
hugovk commented on Aug 8, 2024
Triage: closing because the PR has been merged, please re-open if still needed. Thanks!
Testing an element's truth value is deprecated