Poem converts cases differently than serde

[banool]

Code demonstrating the issue:

use serde::{Deserialize, Serialize};
use poem_openapi::{Object, Union};
use poem_openapi::types::ToJSON;

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize, Object)]
pub struct Ed25519Signature {}

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize, Object)]
pub struct MultiEd25519Signature {}

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize, Object)]
pub struct MultiAgentSignature {}

#[derive(Clone, Debug, PartialEq, Serialize, Deserialize, Union)]
#[serde(tag = "type", rename_all = "snake_case")]
#[oai(one_of, discriminator_name = "type", rename_all = "snake_case")]
pub enum TransactionSignature {
    Ed25519Signature(Ed25519Signature),
    MultiEd25519Signature(MultiEd25519Signature),
    MultiAgentSignature(MultiAgentSignature),
}

fn main() {
    let test = TransactionSignature::Ed25519Signature(Ed25519Signature{});
    println!("test: {}", serde_json::to_string(&test).unwrap());
    println!("test: {}", test.to_json().unwrap());
}

Output:

test: {"type":"ed25519_signature"}
test: {"type":"ed_25519_signature"}

I feel we should strive to make the behavior match here.

[banool]

Upon diving deeper, I see Poem uses inflector while serde uses its own thing: https://github.com/serde-rs/serde/blob/master/serde_derive/src/internals/case.rs.

[banool]

I don't think I have the context necessary to make a change here, do you have any ideas @sunli829? I figure the best way would be to leverage serde more directly (perhaps optionally, only if the user wants) instead of implementing rename_all separately. This kind of thing would enable #329 too.

[banool]

Seems like the serde stuff is accessible: https://crates.io/crates/serde_derive_internals. I'll make a PR if you think the idea to switch over makes sense @sunli829.

[sunli829]

Can't use serde directly, because can't fully support the serde annotation, I currently use the Inflector crate for case conversion, I will try another one.

[banool]

Perhaps relying on serde_derive_internals might be the best option? Let me know if you're working on this, if not I can try implement it myself :)

[sunli829]

I'm working on this.

[sunli829]

I've push changes in master branch, please help test it.

[banool]

Works perfectly, thanks a lot! Using it in aptos-labs/aptos-core#2764 to great effect.