regression: rustfmt using input from stdin emits empty output when using #![rustfmt::skip]

[jhgg]

Since #5094 - rustfmt now emits nothing to stdout if reading a file with #![rustfmt::skip] is provided via stdin.

For example, running echo '#![rustfmt::skip]\n\nfn main() { }' | rustfmt no longer emits anything to stdout.

Rust-analyzer uses rustfmt to format files, and sends rustfmt the file contents to format via stdin.

This has caused an interesting issue, where rustfmt emits nothing, so rust-analyzer deletes the contents of the file being formatted: rust-lang/rust-analyzer#12458

[calebcartwright]

Thank you for the report and bisection!

[calebcartwright]

As I recall the custom tool attributes have only been available on nightly for a while now, so I don't think there's any need to pursue any kind of backport. I'm hoping to cut a new release sometime within the next couple days, and once available on nightly I'll drop a note on the RA issue to share the version that contains the fix