macro/src/lib.rs

#![allow(
    clippy::large_enum_variant,
    clippy::new_without_default,
    clippy::or_fun_call,
    clippy::toplevel_ref_arg,
    clippy::useless_let_if_seq
)]

extern crate proc_macro;

mod expand;
mod namespace;
mod syntax;

use crate::namespace::Namespace;
use proc_macro::TokenStream;
use syn::{parse_macro_input, ItemMod};

/// `#[cxx::bridge] mod ffi { ... }`
///
/// Refer to the crate-level documentation for the explanation of how this macro
/// is intended to be used.
///
/// The only additional thing to note here is namespace support — if the
/// types and functions on the `extern "C"` side of our bridge are in a
/// namespace, specify that namespace as an argument of the cxx::bridge
/// attribute macro.
///
/// ```
/// #[cxx::bridge(namespace = mycompany::rust)]
/// # mod ffi {}
/// ```
///
/// The types and functions from the `extern "Rust"` side of the bridge will be
/// placed into that same namespace in the generated C++ code.
#[proc_macro_attribute]
pub fn bridge(args: TokenStream, input: TokenStream) -> TokenStream {
    let _ = syntax::error::ERRORS;

    let namespace = parse_macro_input!(args as Namespace);
    let ffi = parse_macro_input!(input as ItemMod);

    expand::bridge(&namespace, ffi)
        .unwrap_or_else(|err| err.to_compile_error())
        .into()
}