forma-ir-derive

#[derive(PageProps)] supplies Forma's Rust page contract. Use its re-export from forma-ir; applications do not need a direct dependency on this proc-macro crate. The historical version 0.0.0 was a reservation placeholder. The current 3.0.0 implementation supports the declared FMIR props schema.

use forma_ir::PageProps;

#[derive(PageProps)]
struct User {
    display_name: String, // TypeScript displayName
    #[props(rename = "account-id")]
    account_id: u64,
    last_seen: Option<std::time::SystemTime>,
    roles: Vec<Role>,
}

#[derive(PageProps)]
enum Role {
    #[props(rename = "reader")]
    Reader,
    #[props(rename = "editor")]
    Editor,
}

Named structs and unit enums may contain bool, String, integer types through 64 bits, f32, f64, SystemTime, Option<T>, Vec<T>, and other derived named types. Struct fields default to camelCase; enum literals retain their variant names unless renamed. Attributes belong on fields or enum variants. Tuples, unit structs, enum payloads/discriminants, generic declarations, recursive shapes, maps, sets, references and unrestricted JSON values are unsupported. Invalid shapes, attributes and duplicate final names report the offending declaration. Recursive shapes return a bind error before value encoding.

The derive uses FMIR's actual PropsSchema and records each Rust field's source file, line and column. Binding compares fields by name, regardless of order. Every TypeScript field must exist in Rust, including optional fields. A required Rust field may satisfy an optional TypeScript field; a Rust Option cannot satisfy a required TypeScript field. Enum sets must match exactly. Extra Rust fields produce warnings and are never encoded.

forma_ir::props::BoundProps<P> verifies a module once and retains it immutably. Each call to encode projects only the declared fields, omits absent object fields, and preserves absent array elements as null placeholders. Integer checks run before any floating-point conversion and enforce ±(2^53−1); floats must be finite. Dates encode signed epoch milliseconds, truncating sub-millisecond precision toward zero, with the valid JavaScript Date bound ±8.64e15 ms. Failures include route, property path and both declarations where available. A development reload constructs a fresh binding for the new module.

Licensed under the MIT licence.