Derive Macro SerializeDisplayAlt

#[derive(SerializeDisplayAlt)]
{
    // Attributes available to this derive:
    #[serde_with]
}

Serialize value by using its Display implementation with the “alternate” (#) format flag

This derive implements serde::Serialize for any type that already implements std::fmt::Display, emitting its string form using the alternate formatting specifier ({:#}) instead of the normal {}. In other words, rather than calling format!("{}", self), it calls format!("{:#}", self).

Ensure that your type implements Display, or you will get a compile‐error such as:

error[E0277]: `MyType` doesn't implement `std::fmt::Display`

Deserialization from strings via std::str::FromStr is handled by the companion DeserializeFromStr derive.

Attributes

You may customize which serde_with crate is used (for renamed or re-exported crates) via the same attribute namespace:

• #[serde_with(crate = "...")] When your workspace renames or re-exports serde_with, use this to point at the correct path. For example:

  #[derive(SerializeDisplayAlt)]
  #[serde_with(crate = "my_forked_serde_with")]
  pub struct Foo(/* … */);

Example

use std::fmt;
use serde_with::{SerializeDisplayAlt, DeserializeFromStr};

#[derive(Debug, Clone, SerializeDisplayAlt, DeserializeFromStr)]
#[serde(transparent)]
pub struct MyType(u32);

impl fmt::Display for MyType {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if f.alternate() {
            // Alternate formatting: hex with 0x prefix
            write!(f, "0x{:X}", self.0)
        } else {
            // Standard formatting: decimal
            write!(f, "{}", self.0)
        }
    }
}

let v = MyType(15);
// SerializeDisplayAlt always uses `{:#}`, so this yields `"0xF"`
assert_eq!(r#""0xF""#, serde_json::to_string(&v).unwrap());