Rust / Prost : How do add Debug to structs & unions?

Question

It looks like the prost protobuf generator only adds derive(Debug) to generated enum types (and only enums not inside a pub mod block). None of the generated structs, or unions have it applied. How can I get prost to add it to everything?

Using Prost version 0.9 and rustic 1.56

I don't see the logic in trying to implement `Debug` on a `union` safely. — Optimistic Peach, Nov 05 '21 at 18:06
I meant union in the protobuf, not rust. I don't think prost generates rust unions. — West_JR, Nov 07 '21 at 03:03

score 1 · Accepted Answer · answered Nov 07 '21 at 21:28

1

Prost does derive Debug on everything. But you need prost::Messaeg in scope or you'll get an error about missing Debug traits.

answered Nov 07 '21 at 21:28

West_JR

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2
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could you please elaborate on this more? – taras Jan 04 '22 at 20:03

score -1 · Answer 2 · answered Nov 06 '21 at 15:19

prost doesn't have an option to turn that on so you have to do it yourself.

If you want to implement a trait for a type. You need to have either the trait or the type in your library/binary.

Since the trait is in std and the type is in an external crate the best you can do is create a unit struct to wrap the type. Then implement Debug for that.

use std::fmt;

struct DebugStruct(NonDebugEnum);

impl fmt::Debug for DebugStruct {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        todo!()
    }
}

fn main() {
    let wrapped = DebugStruct(NonDebugEnum::Example);
    println!("{:?}", wrapped);
}

You will have to come up with the actual logic of how to format it.

So I have to add all the fields manually? And if the protobuf ever changes, I either won't compile anymore or no longer be complete? — West_JR, Nov 07 '21 at 02:57
Yes pretty much. Or you can ask the developers of the crate to add that functionality. It isn't a very nice situation either way. — Hadus, Nov 07 '21 at 11:31

Rust / Prost : How do add Debug to structs & unions?

2 Answers2