Clippy warnings in auto generated code: derive-partial-eq-without-eq

[arvid-norlander]

I'm getting many instances of clippy::derive-partial-eq-without-eq (an non-default lint that I like to enable for my code) for auto-generated code from prost/prost-build. E.g.

warning: you are deriving `PartialEq` and can implement `Eq`
   --> .../target/debug/build/crate_name-8fbbd81e799a35b3/out/analysis.rs:216:17
    |
216 | #[derive(Clone, PartialEq, ::prost::Message)]
    |                 ^^^^^^^^^ help: consider deriving `Eq` as well: `PartialEq, Eq`

This happens on for example the following protobuf code (which comes from the bazel project):

syntax = "proto3";

// ...

// A set of fragment options.
message FragmentOptions {
  // The name of this set of fragment options.
  string name = 1;

  // The options themselves, in sorted order by name.
  repeated Option options = 2;
}

// A fragment option.
message Option {
  // The name of the option.
  optional string name = 1;

  // The value of the option.
  optional string value = 2;
}

For some reason Prost marks Option as implementing Eq, but not FragmentOptions. Which triggers clippy. And I think clippy is right in this case.

Note that there is a workaround available:

mod proto {
    #![allow(clippy::derive_partial_eq_without_eq)]
    #![allow(clippy::doc_lazy_continuation)]
    #![allow(clippy::enum_variant_names)]
    // ...
    include!(concat!(env!("OUT_DIR"), "/includes.rs"));
}

Most of those are reasonable to ignore for protobuf generated code, but derive_partial_eq_without_eq looks like an actual problem to my eye in the generated code.

[caspermeijn]

I did some work to automatically derive Eq where possible in #1175

That has not yet been released. Can you verify the clippy warnings are fixed on the main branch of prost-build?

[arvid-norlander]

I tried that, using commit fcf610e, but I still get a bunch of these warnings, including the one from the example snippet above.

I did this using

[patch.crates-io]
prost-build = { git = 'https://github.com/tokio-rs/prost.git' }

It seems it was correctly using the newer version:

   Compiling prost-derive v0.13.5 (https://github.com/tokio-rs/prost.git#fcf610ed)
   Compiling prost v0.13.5 (https://github.com/tokio-rs/prost.git#fcf610ed)
   Compiling prost-types v0.13.5 (https://github.com/tokio-rs/prost.git#fcf610ed)
   Compiling prost-build v0.13.5 (https://github.com/tokio-rs/prost.git#fcf610ed)