Derive Macro GraphValue 

#[derive(GraphValue)]
{
    // Attributes available to this derive:
    #[graph]
}

Derive macro for converting between Rust types and Value.

Structs

Structs are converted to Value::Record with field names as keys.

#[derive(GraphValue)]
struct Person {
    name: String,
    age: i64,
}

Enums

Enums are converted to Value::Variant with the variant index as tag.

#[derive(GraphValue)]
enum Shape {
    Circle(f64),           // tag 0, payload = radius
    Rectangle(f64, f64),   // tag 1, payload = tuple(width, height)
    Point,                 // tag 2, no payload
}

Attributes

• #[graph(crate = "path")] - Specify the crate path (default: packr_abi)
• #[graph(rename = "name")] - Use a different name for field/variant
• #[graph(tag = N)] - Use explicit tag number for variant
• #[graph(forward_compatible)] - Tolerant decode for schema evolution on a STRUCT: a missing field defaults and an extra field is ignored, so appending a field is decode-safe both ways (old build reads new data; new build reads old data — no rollback data loss, no hand-written pad-missing migration). Default (absent) is a strict field-count decode. Named structs match fields by name (add/remove/reorder tolerated); tuple structs are positional, so only APPENDING a trailing field is safe. Encode is unchanged (wire-compatible).