Many regular expression tests fail with CMake 3.31

[musicinmybrain]

With CMake 3.30.5, as a “control” to show that I’m running the tests correctly:

$ gh repo clone editorconfig/editorconfig-core-py
$ cd editorconfig-core-py
$ python3.13 -m venv _e
$ . _e/bin/activate
(_e) $ pip install -e .
(_e) $ cmake .
(_e) $ ctest .
[…]
100% tests passed, 0 tests failed out of 197

Total Test time (real) =  56.53 sec

Ok, great! Now, upgrading CMake from 3.30.5 to 3.31.1, and re-running just ctest .:

(_e) $ ctest .
[…]
90% tests passed, 20 tests failed out of 197

Total Test time (real) =  59.15 sec

The following tests FAILED:
          2 - meta_multiline (Failed)
          3 - star_single_ML (Failed)
          4 - star_zero_ML (Failed)
          5 - star_multiple_ML (Failed)
          7 - star_after_slash_ML (Failed)
          8 - star_matches_dot_file_after_slash_ML (Failed)
        131 - tab_width_default_ML (Failed)
        132 - tab_width_default_indent_size_tab_ML (Failed)
        133 - indent_size_default_ML (Failed)
        136 - indent_size_default_with_tab_width_ML (Failed)
        137 - lowercase_values1_ML (Failed)
        138 - lowercase_values2_ML (Failed)
        141 - repeat_sections_ML (Failed)
        142 - basic_cascade_ML (Failed)
        148 - blank_lines_between_properties_ML (Failed)
        152 - spaces_before_middle_property_ML (Failed)
        154 - comment_between_props_ML (Failed)
        158 - octothorpe_comment_between_props_ML (Failed)
        172 - parent_and_current_dir_ML (Failed)
        190 - unset_indent_size_ML (Failed)

All of the failing tests have output similar to

  2/197 Test   #2: meta_multiline ............................***Failed  Required regular expression not found. Regex=[^[
]*answer=42[
]+$
]  0.50 sec

I’m not sure quite what changed here, or how to fix it. I didn’t see anything obviously relevant in https://cmake.org/cmake/help/latest/release/3.31.html.

[musicinmybrain]

Full output from ctest .