long lines do not get broken off at line-length

[Morriz]

Describe the bug

Lines do not get cut up after line-length.

According to @JelleZijlstra in issue #1802 the following should work but it does not:

To Reproduce

For example, take this code:

black -v --preview -c 'long = "This is a long line that is longer than 88 characters. I expect Black to shorten this line length."'
Using configuration from project root.
line_length: 88
preview: True
target_version: ['py311']
long = "This is a long line that is longer than 88 characters. I expect Black to shorten this line length."
reformatted <string>
All done! ✨ 🍰 ✨

Expected behavior

Environment

• Black's version: 24.2.0
• OS and Python version: OSX 14.2.1 Sonoma

[JelleZijlstra]

This feature has been relegated to --unstable mode because it is too, well, unstable. I recently proposed to give up on it (#4208). Any related discussion can happen there.