Black is not honoring fmt: off for comment changes

[nijel]

Describe the bug

black since 23.1.0 breaks Munin magic markers without a way to override.

To Reproduce

For example, take this code:

# fmt: off
#%# family=auto
#%# capabilities=autoconf
# fmt: on

And run it with these arguments:

$ black file.py

The resulting output is:

# fmt: off
# %# family=auto
# %# capabilities=autoconf
# fmt: on

Expected behavior

The block between fmt: off and fmt: on should not be changed.

Environment

• Black's version: 23.1.0
• OS and Python version: Linux/Python 3.11

Additional context

Seem to be related to #2919, it might be a separate bug there as well, as it talks only about #%% (note the double %). So, it might be two bugs here:

• fmt: off not honored
• #%% formatting being actually applied to #%

[scotran]

Taking a look at this. This seems like part of a known limitation noted in the fmtonoff.py tests: some comments in between fmt: off and fmt: on, it's a weird issue. A simple fix would just include % as part of the comment exceptions, COMMENT_EXCEPTIONS, but might go against what the previous commit wanted - if this is fine, then that's an easy fix. The bigger fix would be to fix comment formatting in between fmt: off/on altogether.