How to get renamed enum name from enum value?

So I have

#[derive(Deserialize, Clone, Debug, Copy)]
pub enum ComparisonOperators {
    #[serde(rename = "=")]
    EQ,
    #[serde(rename = "!=")]
    NEQ,
    #[serde(rename = ">")]
    GT,
    #[serde(rename = ">=")]
    GE,
    #[serde(rename = "<")]
    LT,
    #[serde(rename = "<=")]
    LE,
}

I want to get from let i = ComparisonOperators::GE to ">=". Can I do this by not adding a mapper?

You can add the Serialize tag, and then use the serde_json to serialize to a String as per your attributes renaming:

use serde::{Deserialize, Serialize};
use serde_json; // 1.0.78

#[derive(Deserialize, Serialize, Clone, Debug, Copy)]
pub enum ComparisonOperators {
    #[serde(rename = "=")]
    EQ,
    #[serde(rename = "!=")]
    NEQ,
    #[serde(rename = ">")]
    GT,
    #[serde(rename = ">=")]
    GE,
    #[serde(rename = "<")]
    LT,
    #[serde(rename = "<=")]
    LE,
}

fn main() {
    let tag = serde_json::to_string(&ComparisonOperators::EQ).unwrap();
    println!("{tag}");
}

Playground

You can even implement display for your enum based on that:

impl fmt::Display for ComparisonOperators {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", serde_json::to_string(self).unwrap())
    }
}

Playground

Remember that Display gives you a ToString implementation for free.