"[\n\n]" doesn't pass topiary's idempotence check.

[maxim-uvarov]

> "[\n\n]" | save -f bug.nu; topiary format bug.nu
[2025-11-23T22:57:41Z ERROR topiary_core] Failed idempotence check
[2025-11-23T22:57:41Z ERROR topiary_core] Diff < left / right > :
     [

    >
     ]


[2025-11-23T22:57:41Z ERROR topiary::error] The formatter did not produce the same
    result when invoked twice (idempotence check).

    If this happened with the built-in query files, it is a bug. It would be
    helpful if you logged this error at
    https://github.com/tweag/topiary/issues/new?assignees=&labels=type%3A+bug&template=bug_report.md

[blindFS]

Thanks for reporting this bug, I can confirm the reproduction, even with a single \n.

The problem is that new newline characters following the list start [ in a multiline setup get absorbed into the list_body node, where it should leave an anonymous "\n" node ideally.

What's worse:

use foo.nu [

]

Will cause a parser error.

I think the best way to fix this is some changes on the parser side, I'll see what I can do.