Blog post on removing the Clippy plugin interface

[flip1995]

Clippy is removing its plugin interface rust-lang/rust-clippy#4714. Even though the plugin interface has been deprecated for a long time, we want to provide some instructions on how to migrate from the plugin interface.

Rendered

cc @phansch @Manishearth

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[alexcrichton]

r? @Manishearth

[tesuji]

Suggested change

	description: "Now that compiler plugins are deprecated, Clippy is also removing its plugin interface"
	description: "Clippy is removing its deprecated plugin interface"

[flip1995]

Hm that is practically the title then.

[tesuji]

cc @Centril for wording

[flip1995]

Thanks for the reviews!

[nikomatsakis]

I wonder if this would be better suited to the main rust blog? It seems like the audience is perhaps closer to "all Rust users" than "all Rust contributors".

[dtolnay]

I think this would typically be the wrong guidance. People used feature = "clippy" because the canonical lint suppression used to be:

#[cfg(feature = "clippy", allow(name_of_lint))]

The correct migration would be to a tool attr:

#[allow(clippy::name_of_lint)]

There might be remaining use cases for #[cfg(feature = "cargo-clippy")] but it would be extremely unusual, right?

[flip1995]

This is already handled by rustc. Running cargo clippy on

#![cfg_attr(feature = "cargo-clippy", deny(if_not_else))]
// code ...

emits

warning: lint name `if_not_else` is deprecated and may not have an effect in the future. Also `cfg_attr(cargo-clippy)` won't be necessary anymore
 --> src/main.rs:1:44
  |
1 | #![cfg_attr(feature = "cargo-clippy", deny(if_not_else))]
  |                                            ^^^^^^^^^^^ help: change it to: `clippy::if_not_else`
  |
  = note: `#[warn(renamed_and_removed_lints)]` on by default

[flip1995]

Also I wanted to write a clippy lint, that detects cfg_attr(cargo-clippy) and suggests to remove this, but never got to finish this lint.

https://github.com/flip1995/rust-clippy/commits/cfg_attr_lint

[flip1995]

I wonder if this would be better suited to the main rust blog?

I moved it to the main rust blog. If anyone thinks it should stay in inside-rust, I can move it back anytime.

[flip1995]

cc @nikomatsakis @Centril @Manishearth

We'd like to merge rust-lang/rust-clippy#4714, but would like to publish this blog post first. Are there any more comments to this post? Note that it now aimed at the main rust blog.

Should I adapt the date in the file name before merging?

[nikomatsakis]

Hmm. I know I suggested the main blog -- but I'm second guessing that. My main concern is that -- reading this post as a non-clippy user -- I am a bit confused as to its significance. My assumption is that you are removing a "little used" way to integrating clippy, and that this won't affect most users. But the post doesn't make that context clear. I worry that casual readers will be confused into thinking "what's this? clippy is being removed?"

I suppose this isn't really a question as to which blog is appropriate but rather just feedback on the post -- it'd be good to add a few lines putting this change into some greater context. For example: "We don't expect this change to effect most users. It only effects you if you are using clippy in this particular way, which is not the common path." (obviously with more details).

Of course, if I am wrong, and this actually does effect a lot of users, ok!

[Manishearth]

@nikomatsakis right, that's why we wanted it on the inside blog, it doesn't affect most folks but we should write about it somewhere and link to it on the forums.

[flip1995]

@nikomatsakis I added the note and moved it back to the inside rust blog.

[nikomatsakis]

OK, sorry for the confusion! going to merge.