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derive_enum_dataframe

miniextendr_macros::dataframe_derive::enum_expansion

Function derive_enum_dataframe 

Source 
pub(super) fn derive_enum_dataframe(
    row_name: &Ident,
    input: &DeriveInput,
    data: &DataEnum,
    df_name: &Ident,
    attrs: &DataFrameAttrs,
) -> Result<TokenStream>
Expand description

Derive DataFrameRow for an enum with #[dataframe(align)].

Generates a companion struct where every column is Vec<Option<T>>, with None fill for fields absent in a given variant. This is the enum counterpart of super::derive_struct_dataframe.

§Generated items

  • Companion struct {Name}DataFrame with Vec<Option<T>> columns (field-name union)
  • Optional _tag: Vec<String> column for variant discrimination
  • impl IntoDataFrame (converts companion struct to R data.frame)
  • impl From<Vec<Enum>> (sequential row->column transposition)
  • from_rows() / from_rows_par() methods on the companion struct
  • to_dataframe() / DATAFRAME_TYPE_NAME associated items on the enum

§Variant support

  • Named variants ({ field: T }): fields contribute by name to the unified schema
  • Tuple variants ((T, U)): fields are named _0, _1, etc.
  • Unit variants: contribute no columns (only tag if present)

§Auto-expand fields

Fields with #[dataframe(expand)] on Vec<T> types get dynamic column counts determined at runtime from the maximum row length across all rows. These are tracked separately from the static ColumnRegistry.

Returns Err if the enum has no variants or if type conflicts arise without #[dataframe(conflicts = "string")].