Documentation and Target Extensions

@doc

Attach one string to an annotation-bearing declaration or member:

@doc("A public account identifier.")
struct Account {
    @doc(text = "Stable across API versions.") string id;
};

The string can be positional or named value, text, or doc. Generators consume documentation through their documentation renderers, such as Rust doc comments, TypeScript JSDoc, and OpenAPI descriptions. Use one @doc per declaration: the shared renderer reads the first one rather than joining several annotations. It reads string literals, not string constant references. Documentation does not change validation, serialization, or version availability.

@derive

Allowed on structs, unions, enums, bitsets, bitmasks, typedefs, natives, and exceptions. Supply target derive names as positional values:

@derive(Eq)
struct AccountKey {
    string id;
};

The Rust generator consumes derives on structs, unions, enums, bitsets, bitmasks, and exceptions, adding them to the generated derives and deduplicating them. Typedef and native positions pass lint, but render type aliases without these derives. A requested derive must apply to the generated type and its members, and its macro or trait must be available to the consuming Rust crate. This annotation does not define new IDL traits or validator behavior in other targets.

Rust attribute extensions

The Rust generator recognizes the rust- and rust_ prefixes at supported rendering sites and removes the prefix when rendering a Rust attribute:

@rust_non_exhaustive
struct Account {
    string id;
};

The struct receives #[non_exhaustive]. These attributes are target-specific: XIDL does not check that their Rust syntax, names, or effects are valid. The target compiler and the consuming crate own that validation. Keep transport and lifecycle semantics in their built-in annotations instead of hiding them in a Rust attribute.

Recognized names without portable effects

Spelling	What recognition means
@rust(value)	Registered with one required value and any annotation-bearing position; no general code-injection behavior is implemented
rust-..., rust_...	Exempt from built-in lint checks; Rust renderers can pass through attributes at supported sites
ts-..., ts_...	Exempt from built-in lint checks; no general TypeScript attribute passthrough behavior is implemented
Other project annotations	Reported as unknown-annotation warnings; recognition as project metadata does not create a generator extension

The prefix exemption concerns lint only. It does not make an unsupported annotation portable, and --deny warnings does not validate target compiler attributes. Inspect the rendered attributes and compile the intended target when using an extension.

For the supported output targets and combinations, see Target Generators.