bpo-34941: Fix searching Element subclasses.

[serhiy-storchaka]

Methods find(), findtext() and findall() of xml.etree.ElementTree.Element
were not able to find chldren which are instances of Element subclasses.

https://bugs.python.org/issue34941

[jackjansen]

Neat find, thanks! One remark: should there be a note in the documentation (TreeBuilder section) that the element instance returned by the element_factory should be an instance of (a subclass of) Element?

[serhiy-storchaka]

I am unsure. Some parts of the module requires Element subclasses and raise an error otherwise (e.g. append() ad iter()). Others support duck-typing (like slice assignment and serializing). You have found that some operations work only with exact Elements and silently ignore types. I think we need more changes in master, but I'm unsure what should these changes be: restrict children be instances of Element subclasses or add duck typing support everywhere.

See also bpo-28234.

[scoder]

LGTM

[miss-islington]

Thanks @serhiy-storchaka for the PR 🌮🎉.. I'm working now to backport this PR to: 2.7, 3.6, 3.7.
🐍🍒⛏🤖

[bedevere-bot]

GH-9867 is a backport of this pull request to the 3.7 branch.

[miss-islington]

Sorry, @serhiy-storchaka, I could not cleanly backport this to 3.6 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker b11c5667f99c4f0018e3394c4d07c519d835671a 3.6

[miss-islington]

Sorry, @serhiy-storchaka, I could not cleanly backport this to 2.7 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker b11c5667f99c4f0018e3394c4d07c519d835671a 2.7

[serhiy-storchaka]

In 2.7 cElementTree.Element is not subclassable.

[bedevere-bot]

GH-9868 is a backport of this pull request to the 3.6 branch.