rename_all on a Subcommand applies to variant-struct fields

[epage]

Please complete the following tasks

• I have searched the discussions
• I have searched the existing issues

Rust Version

rustc 1.57.0 (f1edd0429 2021-11-29)

Clap Version

v3.0.6

Minimal reproducible code

use clap::{Parser, Subcommand};

#[derive(Parser, Debug)]
#[clap(author, version, about, long_about = None)]
struct Cli {
    #[clap(long)]
    out_dir: Option<String>,

    #[clap(subcommand)]
    command: Commands,
}

#[derive(Subcommand, Debug)]
#[clap(rename_all = "snake_case")]
enum Commands {
    /// Adds files to myapp
    Add {
        #[clap(long)]
        out_dir: Option<String>,
    },
}

fn main() {
    let cli = Cli::parse();
    dbg!(cli);
}

Steps to reproduce the bug with the above code

$ cargo run -- add --help

Actual Behaviour

test-clap-add 
Adds files to myapp

USAGE:
    test-clap add [OPTIONS]

OPTIONS:
    -h, --help                 Print help information
        --out_dir <OUT_DIR>    

Expected Behaviour

test-clap-add 
Adds files to myapp

USAGE:
    test-clap add [OPTIONS]

OPTIONS:
    -h, --help                 Print help information
        --out-dir <OUT_DIR>    

Additional Context

Found via rust-lang/rustc-perf#1142

Debug Output

No response

[epage]

Since clap specifically tests for this behavior, I got worried about what precedent is set for this so I tested serde

#!/usr/bin/env rust-script

//! ```cargo
//! [dependencies]
//! serde = { version = "1", features = ["derive"] }
//! serde_json = "1"
//! ```

#[derive(serde::Serialize, serde::Deserialize, Debug)]
#[serde(rename_all = "SCREAMING_SNAKE_CASE")]
enum Args {
    One,
    Two { field: String },
}

fn main() {
    let args = Args::One;
    let json = serde_json::to_string(&args).unwrap();
    println!("{}", json);
    let args = Args::Two {
        field: "value".into(),
    };
    let json = serde_json::to_string(&args).unwrap();
    println!("{}", json);
}

$ ./clap-3282.rs
    Finished dev [unoptimized + debuginfo] target(s) in 0.01s
     Running `/home/epage/src/personal/cargo-script-mvs/target/debug/rust-script ./clap-3282.rs`
"ONE"
{"TWO":{"field":"value"}}

Looks like serde does not apply rename_all recursively which makes sense because variants and fields are very different and can have different naming needs.

[epage]

Thinking about it more, I think with it being an id, it is fine being skipped by rename_all, especially since we set value_name. However, I could see us providing more specialized renames, rename_flags, rename_commands, rename_values