Add `text_len` to `TextWrapper` for ANSI and variable character width awareness

Feature or enhancement

Proposal:

This is a proposal to add a text_len parameter to textwrap.wrap, textwrap.fill, textwrap.shorten and textwrap.TextWrapper.

That way we can teach these functions how to measure the length of visible text.

The main use-case is ignoring ANSI sequences like so:

>>> import re, textwrap
>>> visible_len = lambda s: len(re.sub(r'\x1b\[[0-9;]*m', '', s))
>>> colored = 'normal \x1b[31mcolored\x1b[0m words here'
>>> lines = textwrap.wrap(colored, width=14, text_len=visible_len)
>>> [re.sub(r'\x1b\[[0-9;]*m', '', line) for line in lines]
['normal colored', 'words here']

This allow flexibility without having to maintain or introduce full ANSI awareness to all the string-manipulating utilities.

And I am pretty sure some users can come up with creative usage other than ANSI, and it provides a future escape-hatch.

An implementation is available at #152702

Has this already been discussed elsewhere?

I have already discussed this feature proposal on Discourse

Links to previous discussion of this feature:

This is a direct follow up on https://github.com/python/cpython/issues/142035 , which introduced a local patch in _split_lines via https://github.com/python/cpython/pull/154634 to address that bug. A new issue has been requested by a project member to track the generalization of that local patch.

Linked PRs

• gh-152702

Start by reviewing the implementation in PR #152702 and the related discussion in issues #142035 and #154634. Compare the proposed text_len parameter across textwrap.wrap, fill, shorten, and TextWrapper, then verify that the visible-width use case and existing behavior are covered before considering the work done.