deser-debug

Formats any value that implements deser's Serialize like #[derive(Debug)] would. This is useful when a type is serializable but does not implement Debug (for instance because you want to keep the compile time and binary size of a second derive off your types), when you are generic over Serialize and want to log values, or when you want to implement Debug in terms of Serialize.

The Rust shape of values (struct and variant names, Option, tuples, ...) is taken from their description (see deser::ser::Describe), so for derived types the output matches what #[derive(Debug)] produces, including pretty printing with {:#?}:

use deser::Serialize;
use deser_debug::ToDebug;

#[derive(Serialize)]
struct Point {
    x: i32,
    y: Option<i32>,
}

#[derive(Serialize)]
#[deser(tag = "type")]
enum Shape {
    Circle { center: Point, radius: f64 },
}

let shape = Shape::Circle {
    center: Point { x: 1, y: None },
    radius: 2.5,
};
assert_eq!(
    format!("{:?}", ToDebug::new(&shape)),
    "Circle { center: Point { x: 1, y: None }, radius: 2.5 }"
);

Note that the output shows the Rust value, not the serialized form: the internally tagged enum above is still shown as a Circle variant rather than a map with a type key.

Names are the ones used when serializing: renamed types, variants and fields (for instance with rename_all = "camelCase") are shown with their new names, variants named by integers are shown as numbers and the fields of flattened structs are shown in the struct they are flattened into. Only the shape is taken from the description, which keeps it cheap: types do not carry any extra information for formatting.