Add blog post about deprecating feature = "cargo-clippy"

[flip1995]

I'm not sure, if this blog post should go into the internals Rust blog or the main blog. I put it in the main blog for now as it might affect a bunch of users, but I'm happy to move it to internals.

cc @rust-lang/clippy @Urgau

Rendered

[Urgau]

Great. Looks good to me.

[flip1995]

Thanks for the reviews!

[blyxyas]

Typo (meow)

[flip1995]

@Mark-Simulacrum Not sure who's responsible for merging blog PRs, so pinging you, as I think that you might know: This change will go into nightly with the sync on Thursday (so on Friday), so we'd like to merge this blog post before then. Last open question is: Should this go into Rust internals or the main Rust blog?

[flip1995]

I updated the date in the file name to today. I'd really like to get this merged today, as people will start seeing the deprecation warnings triggering today in nightly: Playground

[Mark-Simulacrum]

A DM on Zulip is probably the most reliable way to get immediate action (i.e. please merge this).

[danielparks]

Hello, this change affects me (I actually wrote the documentation linked in the post). Could you clarify when this takes effect? Currently it reads like this applies now, but:

• ❌ Running cargo clippy on code that uses feature = "cargo-clippy" does not complain.
• ❌ Running cargo +nightly clippy on code that uses feature = "cargo-clippy" does not complain.
• ❌ not(cfg(clippy)) does not work on stable clippy — clippy ignores the cfg and lints the code.
• ✅ not(cfg(clippy)) does work on nightly clippy — clippy ignores the code.

(Naturally these are on latest stable and nightly as of a few minutes ago.)

It would be very helpful to know when I can expect these things to change.

It would not be such a big deal, but I’m having trouble figuring out which issue I should be tracking for stabilization of these changes.

[flip1995]

Oh, I forgot to mention that this currently only works on nightly, and will only be in stable 1.78. I will update the blog post to clarify this. Sorry for the confusion.

[flip1995]

• Running cargo +nightly clippy on code that uses feature = "cargo-clippy" does not complain.

This is surprising. Maybe your nightly is not up-to-date? I tested this on play.rust-lang-org before merging the blog post.

#1264 Here's the update, sorry again for the confusion!

[danielparks]

Thanks!

Running cargo +nightly clippy on code that uses feature = "cargo-clippy" does not complain.

This is surprising. Maybe your nightly is not up-to-date? I tested this on play.rust-lang-org before merging the blog post.

Looks like this has something to do with my code. Clippy properly complains when I tried a minimal test case.

I generate the offensive code in build.rs inside a test crate, so it’s not exactly a common situation. Clippy catches other lints in the generated code though, so I think there may be some sort of bug. I’ll look into it further and raise a new issue once I know more, or discover that I’m doing something silly (sillier than generating 48,000 line match statements, anyway).

Sorry for the confusion! :)

[danielparks]

Issue filed: #12392 — Clippy ignores feature = "cargo-clippy" in generated code.