Clippy wants

[repi]

Wish list of Clippy lints and features & bug fixes we would like to see added/improved/fixed based on the Rust projects we've been developing at Embark.

This is not a complete list, but an attempt to keep a bit of structure for our own sake, and may be of interest for Clippy lint developers as well.

Should have

Lints & Clippy features or fixes that would directly improve or help our workflows

• [Roadmap] Configuration file for lints rust-lang/rust-clippy#6625 (also see Be able to disable/enable Clippy lints globally #22)
• Implicit Inheritance for Workspapce Inheritance rust-lang/cargo#12208
• #[allow(unsafe_code)] should be allowed after SAFETY: docs rust-lang/rust-clippy#8679 (Embark filed)
• Detect redundant always successful assert_eq! rust-lang/rust-clippy#8567 (Embark filed)
• Lint on large std::{include_str!, include_bytes!}; calls. rust-lang/rust-clippy#7005 (Embark filed)
• On 32-bit, usize as f64 recommends f64::from(usize) rust-lang/rust-clippy#3689 (cast_lossless)
• undocumented_unsafe_blocks does not trigger on unsafe trait impls rust-lang/rust-clippy#8505
• clippy --fix falsely detects dirty Git LFS files rust-lang/rust-clippy#8349
• Flag let _ = ... as dangerous rust-lang/rust-clippy#8246
• New lint (unnecessary_safety_comment): reverse of undocumented_unsafe_blocks rust-lang/rust-clippy#7954
• Check for invalid target_arch rust-lang/rust-clippy#7828
• New lint: map then unwrap rust-lang/rust-clippy#7763
• not_unsafe_ptr_arg_deref false positives rust-lang/rust-clippy#3045
• not_unsafe_ptr_arg_deref does not trigger on type aliases and trait methods rust-lang/rust-clippy#8092
• use_self still gives false positives rust-lang/rust-clippy#6902
• Lint request: Safety comment on safe code rust-lang/rust-clippy#6880
• Split missing_docs_in_private_items into various lints rust-lang/rust-clippy#5736 (by @jhpratt)
• lint unused (clippy) allow attributes rust-lang/rust-clippy#3122
• derive_partial_eq_without_eq will trigger for third party crate derives rust-lang/rust-clippy#9320
• derive_partial_eq_without_eq should acknowledge the constraint it adds  rust-lang/rust-clippy#9063
• Temporarily downgrade uninlined_format_args (to pedantic or nursery) rust-lang/rust-clippy#10087
• trait_duplication_in_bounds breaks code  rust-lang/rust-clippy#9961
• needless_pass_by_ref_mut: false positive with closures rust-lang/rust-clippy#11620
• Detect unknown features inside #[cfg(feature = "…")] blocks rust-lang/rust-clippy#11649

Nice to have

Lints & Clippy features or fixes that would be nice to have, but are lower priority to us than the above list.

• unwrap-used not triggering for DashMap rust-lang/rust-clippy#8399
• Prefer instant.elapsed() over Instant::now() - instant rust-lang/rust-clippy#8603
• New lint: suggest using "implicit named arguments" rust-lang/rust-clippy#8368
• [ER] Useless str -> String allocation rust-lang/rust-clippy#8088
• New lint to minimize the unsafe block scope. rust-lang/rust-clippy#8022
• Add copy lint name function to Clippy's lint list rust-lang/rust-clippy#7959
• Improve filtering options for Clippy's lint list rust-lang/rust-clippy#7958
• Lint against shadowing the prelude rust-lang/rust-clippy#8439
• Improve explanation of not_unsafe_ptr_arg_deref rust-lang/rust-clippy#7714
• Suggest std::ptr::swap(a, b) instead of std::mem::swap(&mut *a, &mut *b) rust-lang/rust-clippy#7381
• Explicit unlock for locks rust-lang/rust-clippy#7500
• iter() -> into_iter() rust-lang/rust-clippy#7459
• New lint: suggest the use of Result::unwrap_or_else over Result::map_or_else rust-lang/rust-clippy#7328
• Cargo: check license is valid SPDX license expression rust-lang/rust-clippy#5974
• Lint double negation !count != 0 rust-lang/rust-clippy#5794
• unnecessary_lazy_evaluations does not take cost of expression into account rust-lang/rust-clippy#8522 (by @jhpratt)
• Unecessary mut reference in parameter rust-lang/rust-clippy#8863

Not filed / found

Fixes or enhancements that believe there is no issue for yet, if you find one please do comment and we'll update it here.

• cargo clippy --fix often doesn't work and it is unclear to the user which lints it works for and which it skips
• A lint to require types in crate to be used fully qualified, like log::info!("hej") instead of use log::info; info!("hej") by specifying log crate in clippy.toml section for the lint.
• A lint to disallow returning Option<()> as we've seen that use in code just to (too) easily early out with ? on empty options.

---

Related tracking issues for other Rust components:

• Rust wants #84
• rustfmt wants #83
• rust-analyzer wants #86

[MarijnS95]

You are perhaps also interested in unused-crate-dependencies, were the "false-positives" around multi-target crates figured out / resolved: rust-lang/rust#95513

Seems like you're also tracking this in #16 though :)

[linyihai]

this is a awsome list, thanks

[MarijnS95]

@repi what are your thoughts on the new [lints] table? https://blog.rust-lang.org/2023/11/16/Rust-1.74.0.html

I considered converting to it and submitting a PR here, but a massive downside is that the table isn't forced down on all crates from the workspace; instead every individual workspace member crate has to opt-in by setting [lints] workspace = true.

[repi]

it is unfortunate and a miss as it makes it very error prone to opt into the workspace lints (rather than opting out), we should have tested the new clippy workspace lint setting more in nightly and given feedback about that.

for our main projects we'll likely still use the new [lints] and update every crate to use it (cc @Jake-Shadle ), and likely write some small automation script for CI to verify that it is used in all of them (or maybe fit for cargo-deny, though a bit odd to have in there).

for all of our smaller open source projects we will likely not change to use the new functionality just because of this reason, it is easier to use .cargo/config.toml RUSTFLAGS override and have it automatically be enabled for all crates in the project, or cargo cranky.

hope these new lint support can be improved to be implicitly inherited from the workspace without changes in the future, this seems to be the main discussion issue for that:

• Implicit Inheritance for Workspapce Inheritance rust-lang/cargo#12208

[MarijnS95]

we should have tested the new clippy workspace lint setting more in nightly and given feedback about that.

Same for us, I've been subscribed to the relevant issues but was never able to follow up on testing this.

That said it likely won't have made a difference given the same reasons in the linked issue: this is an MVP, and implicit/forced inheritance is an addition that can be supplied in later updates.

Keep us posted if you figure out some trivial CI tooling, we might adopt that :)