How do I tell clippy to ignore code generated by a macro?

[ilyvion]

Clippy is giving me this:

error: `format!(..)` appended to existing `String`
   --> src/models.rs:648:69
    |
648 | #[derive(Clone, Copy, Debug, Deserialize, Eq, PartialEq, Serialize, ts_rs::TS)]
    |                                                                     ^^^^^^^^^
    |
    = help: consider using `write!` to avoid the extra allocation
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#format_push_string
    = note: `-D clippy::format-push-string` implied by `-D clippy::pedantic`
    = help: to override `-D clippy::pedantic` add `#[allow(clippy::format_push_string)]`
    = note: this error originates in the derive macro `ts_rs::TS` (in Nightly builds, run with -Z macro-backtrace for more info)

and that's great and all, except I have no direct control over the code generated and would like clippy to ignore it (and all macro-generated code, really) without having to stick #[allow()]s on things for code I didn't write¹. How do I do that?

Footnotes

1. Which is assuming I can even do that; sometimes the #[allow()] would need to be placed somewhere I can't even "reach" from the code before it's been processed. ↩

[sueun-dev]

fwiw, I tried to repro this with ts-rs on a few combos and couldn't get the same error: ts-rs 12.0.1 / 11.1.0 on current stable, current nightly, and 1.85 all passed for a small ts_rs::TS derive case. I also checked a bunch of older ts-rs struct-derive versions and didn't hit format_push_string there either.

For the actual question: I don't think there's a user-side “ignore all macro-generated code” switch. Clippy tries to avoid macro expansions where it can, but proc-macro spans can make that messy.

The narrow unblock is to allow just this lint:

cargo clippy -- -D clippy::pedantic -A clippy::format_push_string

or in Cargo.toml:

[lints.clippy]
pedantic = "deny"
format_push_string = "allow"

If you want to keep that lint for handwritten code, then yeah, you'd probably need a tiny repro with your exact ts-rs + rust/clippy versions. I wouldn't treat this as current ts-rs behavior without that, since I couldn't reproduce it on the current releases.

[flip1995]

I don't think there's a user-side “ignore all macro-generated code” switch. Clippy tries to avoid macro expansions where it can, but proc-macro spans can make that messy.

Exactly this ☝️ This lint triggering here is a bug in Clippy.

If you can provide a reproducer, the lint can be fixed to not lint in proc_macros.