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loopctl

`derive/src/` — the `#[derive(Tool)]` crate [feature: derive]

The companion crate loopctl-derive (a Cargo workspace member): three files that turn a Deserialize struct into a full Tool impl.

Files

  • lib.rs — the proc-macro entry point: #[proc_macro_derive(Tool, attributes(tool))], re-exported by loopctl under the derive feature.
  • attr.rs — attribute parsing: container keys (name, description, read_only, concurrency_safe, system_prompt, handler, allow_extra) and field keys (name, description, skip, default); serde-rename agreement checking; the snake-case/acronym-aware name derivation; later-attribute-wins.
  • expand.rs — code generation: the impl Tool (name/description literals, statically emitted json! schema, call that clones the ToolContext, deserializes, and dispatches to the handler — default run), the Rust-type→JSON-Schema map, the Option/serde-default required-list rules, and every spanned error case.

Behavior notes

  • All diagnostics are spanned syn::Errors → normal compile errors at the offending token; the macro itself never panics.
  • Generated code uses loopctl::__private::serde_json — downstream crates need no direct serde_json dependency.
  • The UI test suite (derive/tests/ui/ with trybuild goldens) pins every error message.

Deep dive: The derive macro.