Single register_function entry point in the Rust SDK

Documentation Index

Fetch the complete documentation index at: https://iii.dev/docs/llms.txt

Use this file to discover all available pages before exploring further.

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What changed

// Sync — schemas auto-extracted from the function's argument and return types.
// Accepts both typed handlers and `Fn(Value) -> Result<Value, IIIError>`.
iii.register_function("greet", RegisterFunction::new(greet));

// Async — same as `new` but for async fns. Same dual support.
iii.register_function(
    "http::fetch",
    RegisterFunction::new_async(fetch).description("Fetches a URL"),
);
iii.register_function(
    "echo",
    RegisterFunction::new_async(|input: Value| async move { Ok(input) }),
);

// HTTP-invoked function (Lambda, Cloudflare Workers, etc.) — no local handler.
iii.register_function(
    "ext::lambda",
    RegisterFunction::http(http_config).description("Proxies to a Lambda"),
);

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Handler error type fixed to IIIError

1. Update the return type to Result<R, IIIError>.
2. Either return IIIError::Handler(s) directly, or use ?-propagation: Err::<_, IIIError>("oops".into()) works, as does Err("oops".to_string())? once the function returns Result<_, IIIError>.

// Before
fn greet(input: GreetInput) -> Result<String, String> {
    Ok(format!("Hello, {}!", input.name))
}

// After
fn greet(input: GreetInput) -> Result<String, IIIError> {
    Ok(format!("Hello, {}!", input.name))
}

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Removed

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Why

1. The previous changelog entry already moved register_function_with to (id, handler, options) to match Node and Python. While doing the consumer migration, the redundancy between register_function, register_function_with, and the tuple form became evident: three call shapes, one trait machinery, two helper structs (IIIFn / IIIAsyncFn), and two traits (IntoFunctionHandler, IntoFunctionRegistration) — all serving roughly the same purpose with different ergonomics.
2. With a single entry point, a single registration type, and three constructors (new, new_async, http), the surface area becomes one method and one builder. Schemars’ JsonSchema for Value impl lets new / new_async cover both typed and Value handlers without a separate untyped escape hatch.

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Migration