Module list_derive 

List and Preference Derive Macros

This module implements derive macros for bidirectional Rust struct <-> R list conversion, plus “preference” derives that control how a type is converted to R when returned from #[miniextendr] functions.

List Derives

• #[derive(IntoList)] – Rust struct -> R named/unnamed list
• #[derive(TryFromList)] – R list -> Rust struct

Preference Derives

These marker derives select the IntoR strategy for a type. Only one preference derive should be applied to a given type:

• #[derive(PreferList)] – convert via IntoList::into_list
• #[derive(PreferExternalPtr)] – wrap in ExternalPtr::new
• #[derive(PreferDataFrame)] – convert via ColumnSource::into_column_list
• #[derive(PreferRNativeType)] – convert via AsRNative wrapper

Stacking two of them is a conflict: each derive emits a fixed-name marker const (prefer_conflict_marker), so a second Prefer* produces a guided “duplicate definitions” error pointing at the call-site As* wrappers as the way to choose a representation per return value (see #870).

Field Attributes

• #[into_list(ignore)] – skip this field during IntoList/TryFromList conversion. For TryFromList, ignored fields are filled with Default::default().

Functions

derive_into_list

Derive IntoList for structs (Rust -> R).

derive_prefer_data_frame

Derive PreferDataFrame: emits an IntoR impl that converts to R via ColumnSource::into_column_list, then into_sexp.

derive_prefer_externalptr

Derive PreferExternalPtr: emits an IntoR impl that wraps the value in ExternalPtr::new before converting to SEXP.

derive_prefer_list

Derive PreferList: emits an IntoR impl that converts to R by first calling IntoList::into_list, then into_sexp.

derive_prefer_rnative

Derive PreferRNativeType: emits an IntoR impl that wraps the value in AsRNative(self) before calling IntoR::into_sexp.

derive_try_from_list

Derive TryFromList for structs (R -> Rust).

field_is_ignored 🔒

Check whether a struct field has the #[into_list(ignore)] attribute.

prefer_conflict_marker 🔒

Emit a fixed-name conflict marker so that stacking two Prefer* derives on a single type produces a guided compile error instead of a cryptic E0119 conflicting-IntoR-implementation error.