struct-mapper-derive 0.2.0

Procedural macro implementation for struct-mapper — do not depend on this directly, use struct-mapper instead
Documentation 
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//! # struct-mapper-derive
//!
//! Procedural macro crate for `struct-mapper`.
//! Provides `#[derive(MapFrom)]` and `#[derive(TryMapFrom)]` to auto-generate
//! `impl From<Source> for Target` and `impl TryFrom<Source> for Target`.
//!
//! **Do not depend on this crate directly.** Use `struct-mapper` instead.

use proc_macro::TokenStream;
use syn::{parse_macro_input, DeriveInput};

mod codegen;
mod error;
mod field_match;
mod parse;

/// Derive macro that generates `impl From<Source> for Target` by mapping fields.
///
/// # Usage
///
/// ```rust,ignore
/// use struct_mapper::MapFrom;
///
/// struct UserEntity {
///     name: String,
///     email: String,
/// }
///
/// #[derive(MapFrom)]
/// #[map_from(UserEntity)]
/// struct UserResponse {
///     name: String,
///     email: String,
/// }
///
/// // Now you can do:
/// let entity = UserEntity { name: "Alice".into(), email: "a@b.com".into() };
/// let response: UserResponse = entity.into();
/// ```
///
/// # Field Attributes
///
/// - `#[map(from = "source_field")]` — Map from a differently-named source field
/// - `#[map(skip, default)]` — Skip this field, use `Default::default()`
/// - `#[map(into)]` — Call `.into()` on the source field value
/// - `#[map(with = "path::to::fn")]` — Apply a custom conversion function
#[proc_macro_derive(MapFrom, attributes(map_from, map))]
pub fn derive_map_from(input: TokenStream) -> TokenStream {
    let input = parse_macro_input!(input as DeriveInput);

    match codegen::expand_map_from(&input) {
        Ok(tokens) => tokens.into(),
        Err(err) => err.to_compile_error().into(),
    }
}

/// Derive macro that generates `impl TryFrom<Source> for Target` by mapping fields.
///
/// Use this when one or more field conversions can fail (e.g., type narrowing,
/// parsing, validation). The generated implementation returns
/// `Result<Self, struct_mapper::MapError>`.
///
/// # Usage
///
/// ```rust,ignore
/// use struct_mapper::TryMapFrom;
///
/// struct RawInput {
///     count: i64,
///     name: String,
/// }
///
/// #[derive(TryMapFrom)]
/// #[try_map_from(RawInput)]
/// struct ValidInput {
///     #[map(try_into)]
///     count: u32,     // i64 -> u32 can fail
///     name: String,   // direct (infallible)
/// }
///
/// // Now you can do:
/// let raw = RawInput { count: 42, name: "Alice".into() };
/// let valid: ValidInput = raw.try_into().unwrap();
/// ```
///
/// # Field Attributes
///
/// All `MapFrom` attributes work here, plus:
///
/// - `#[map(try_into)]` — Call `.try_into()` on the source field (fallible)
/// - `#[map(try_with = "path::to::fn")]` — Apply a fallible conversion function
#[proc_macro_derive(TryMapFrom, attributes(try_map_from, map))]
pub fn derive_try_map_from(input: TokenStream) -> TokenStream {
    let input = parse_macro_input!(input as DeriveInput);

    match codegen::expand_try_map_from(&input) {
        Ok(tokens) => tokens.into(),
        Err(err) => err.to_compile_error().into(),
    }
}