Hi,

I am experiencing an error in a CI job in GitHub in some packages I currently maintain (verilog-ext and vhdl-ext, available on MELPA). The error only happens in the `snapshot` build, cached from a recent Emacs version (https://github.com/purcell/nix-emacs-ci).

In both of these packages (verilog-ext and vhdl-ext) I have created an `xref` backend based on tree-sitter. To test it there is an ERT test suite that writes the xref items to a text file with `(pp-default-function #'pp-29)` and compares it with a reference file created previously using the same function.

This test works well with all Emacs versions from 29.1 to 30.1 and with release-snapshot. However with the latest versions it seems something in `pp` or in `xref` might have changed that I am missing and maybe I should update to. Is there any idea of what could it be?

I attach the log of GitHub actions failing job in case it could be useful.

Thanks in advance!