I would prefer to not change PyUnicodeWriter_WriteRepr() in a Python 3.14.x bugfix release. Can you leave it unchanged? Instead, modify list_repr() and tuple_repr() to write<NULL> string explicitly.

We need to modify not only list_repr() and tuple_repr(), but all code that usesPyUnicodeWriter_WriteRepr(). And what about the user code? We leave it with a mine which explodes in rare and most likely not tested case.

In the Python code base, if I read the code correctly, onlytuple_repr() can callPyUnicodeWriter_WriteRepr() withNULL. For example,list_repr() cannot passNULL, becauseitem = Py_NewRef(v->ob_item[i]) crash if the item isNULL.

And what about the user code? We leave it with a mine which explodes in rare and most likely not tested case.

My concern is that if you develop on (the future) Python 3.14.4 withPyUnicodeWriter_WriteRepr() which acceptsNULL, you can get crashes if an user uses Python 3.14.0 which doesn't acceptNULL. I don't think that it's a good idea to change the API in a 3.14.x bugfix release.

Python 3.14.0 is broken. It crashes when you callrepr() for uninitialized list or tuple, and it can crash in other cases. Does it mean that we should not backport the bugfix? I think that it is the nature of bugfix releases that they make the code which failed in earlier releases to pass.

The documentation says thatPyUnicodeWriter_WriteRepr() callsPyObject_Repr() onobj and writes the output intowriter.PyObject_Repr() works with NULL.

If you insist to change PyUnicodeWriter_WriteRepr() API, please add aversionchanged markup to document that the API changed.

If we don't fix it in 3.14, we will need a versionchanged for 3.15. But we rarely add versionchanged for bugfixes, especially if the feature was added in the same version.

I'm suggesting to add aversionchanged markup in the 3.14 change to say that the API changed in Python 3.14.x.

Done. Created also a PR for adding in in main.