Formatting file empties file

[Ten0]

rust-analyzer version: 0add6e9 2021-12-20 stable
rustc version: rustc 1.58.0 (02072b482 2022-01-11)

Formatting files that have @generated instead empties the whole file.
This issue will hit more users as we had to use rustfmt +nightly before to encounter it, while with the 1.58 release all users will be affected.

This only happens if format_generated_files is false in rustfmt.toml (newly released in 1.58).

[bjorn3]

This is a rustfmt bug. It doesn't return any code if the input to format contains @generated.

$ echo "//@notgenerated\nfn   foo() {}" | rustfmt
//@notgenerated
fn foo() {}
$ echo "//@generated\nfn   foo() {}" | rustfmt

Instead it should emit the original code.

[bjorn3]

Opened rust-lang/rustfmt#5172.

[bjorn3]

Rust 1.58.1 will contain a fix (rust-lang/rust#93071). It will probably be released tomorrow.