Cargo fmt and rustfmt are using different editions by default

[ranjeethmahankali]

If I run cargo fmt on my project that targets the 2024 edition, it formats it correctly. If I just run rustfmt on a file, it targets the 2021 edition by default. To be consistent with cargo fmt I have to run rustfmt --edition 2024 <file>.

Is this discrepancy intended?

I noticed this because my editor automatically runs rustfmt on save. So the files keep switching back to 2021 formatting whenever I edit them. I can tweak my editor to not do this, but I figured this might be an unintentional bug that affects others.

[ytmimi]

Yes. It's actually the case that rustfmt uses a default edition of 2015 (it's just that there are no formatting differences between 2015, 2018, and 2021). Default formatting changes were introduced with 2024, and that's why you're seeing differences.

cargo fmt is just a wrapper around rustfmt that first looks up the edition in your Cargo.toml so if you've set the edition to 2024 in there, then that's the edition cargo fmt is going to run with.

For consistency between rustfmt and cargo fmt the recommendation is to add a rustfmt.toml file to your project if you don't already have one, and add a configuration for style_edition. For example:

style_edition = "2024"

I think we meant to update the docs to include these details, but haven't done so yet.

[karolzwolak]

@rustbot claim