napi-rs/crates/macro/src/lib.rs

#[cfg(feature = "compat-mode")]
mod compat_macro;
mod parser;

#[macro_use]
extern crate syn;
#[macro_use]
extern crate napi_derive_backend;
#[macro_use]
extern crate quote;
use napi_derive_backend::{BindgenResult, TryToTokens};

#[cfg(feature = "type-def")]
use napi_derive_backend::{ToTypeDef, TypeDef};
use parser::ParseNapi;
use proc_macro::TokenStream as RawStream;
use proc_macro2::TokenStream;
use std::env;
#[cfg(feature = "type-def")]
use std::{
  fs,
  io::{BufWriter, Result as IOResult, Write},
};
#[cfg(feature = "compat-mode")]
use syn::{fold::Fold, parse_macro_input, ItemFn};

/// ```ignore
/// #[napi]
/// fn test(ctx: CallContext, name: String) {
///   "hello" + name
/// }
/// ```
#[proc_macro_attribute]
pub fn napi(attr: RawStream, input: RawStream) -> RawStream {
  match expand(attr.into(), input.into()) {
    Ok(tokens) => {
      if env::var("DEBUG_GENERATED_CODE").is_ok() {
        println!("{}", tokens.to_string());
      }
      tokens.into()
    }
    Err(diagnostic) => {
      println!("`napi` macro expand failed.");

      (quote! { #diagnostic }).into()
    }
  }
}

fn expand(attr: TokenStream, input: TokenStream) -> BindgenResult<TokenStream> {
  let mut item = syn::parse2::<syn::Item>(input)?;
  let opts = syn::parse2(attr)?;

  let mut tokens = proc_macro2::TokenStream::new();

  let napi = item.parse_napi(&mut tokens, opts)?;
  napi.try_to_tokens(&mut tokens)?;

  #[cfg(feature = "type-def")]
  if let Ok(type_def_file) = env::var("TYPE_DEF_TMP_PATH") {
    if let Err(e) = output_type_def(type_def_file, napi.to_type_def()) {
      println!("Failed to write type def file: {:?}", e);
    };
  }

  Ok(tokens)
}

#[cfg(feature = "type-def")]
fn output_type_def(type_def_file: String, type_def: TypeDef) -> IOResult<()> {
  let file = fs::OpenOptions::new()
    .append(true)
    .create(true)
    .open(type_def_file)?;

  let mut writer = BufWriter::<fs::File>::new(file);
  writer.write_all(type_def.to_string().as_bytes())?;
  writer.write_all("\n".as_bytes())
}

#[cfg(feature = "compat-mode")]
#[proc_macro_attribute]
pub fn contextless_function(_attr: RawStream, input: RawStream) -> RawStream {
  let input = parse_macro_input!(input as ItemFn);
  let mut js_fn = compat_macro::JsFunction::new();
  js_fn.fold_item_fn(input);
  let fn_name = js_fn.name.unwrap();
  let fn_block = js_fn.block;
  let signature = js_fn.signature.unwrap();
  let visibility = js_fn.visibility;
  let new_fn_name = signature.ident.clone();
  let execute_js_function =
    compat_macro::get_execute_js_code(new_fn_name, compat_macro::FunctionKind::Contextless);

  let expanded = quote! {
    #[inline(always)]
    #signature #(#fn_block)*

    #visibility extern "C" fn #fn_name(
      raw_env: napi::sys::napi_env,
      cb_info: napi::sys::napi_callback_info,
    ) -> napi::sys::napi_value {
      use std::ptr;
      use std::panic::{self, AssertUnwindSafe};
      use std::ffi::CString;
      use napi::{Env, NapiValue, NapiRaw, Error, Status};

      let ctx = unsafe { Env::from_raw(raw_env) };
      #execute_js_function
    }
  };
  // Hand the output tokens back to the compiler
  RawStream::from(expanded)
}

#[cfg(feature = "compat-mode")]
#[proc_macro_attribute]
pub fn js_function(attr: RawStream, input: RawStream) -> RawStream {
  let arg_len = parse_macro_input!(attr as compat_macro::ArgLength);
  let arg_len_span = arg_len.length;
  let input = parse_macro_input!(input as ItemFn);
  let mut js_fn = compat_macro::JsFunction::new();
  js_fn.fold_item_fn(input);
  let fn_name = js_fn.name.unwrap();
  let fn_block = js_fn.block;
  let signature = js_fn.signature.unwrap();
  let visibility = js_fn.visibility;
  let new_fn_name = signature.ident.clone();
  let execute_js_function =
    compat_macro::get_execute_js_code(new_fn_name, compat_macro::FunctionKind::JsFunction);
  let expanded = quote! {
    #[inline(always)]
    #signature #(#fn_block)*

    #visibility extern "C" fn #fn_name(
      raw_env: napi::sys::napi_env,
      cb_info: napi::sys::napi_callback_info,
    ) -> napi::sys::napi_value {
      use std::ptr;
      use std::panic::{self, AssertUnwindSafe};
      use std::ffi::CString;
      use napi::{Env, Error, Status, NapiValue, NapiRaw, CallContext};
      let mut argc = #arg_len_span as usize;
      let mut raw_args: [napi::sys::napi_value; #arg_len_span] = [ptr::null_mut(); #arg_len_span];
      let mut raw_this = ptr::null_mut();

      unsafe {
        let status = napi::sys::napi_get_cb_info(
          raw_env,
          cb_info,
          &mut argc,
          raw_args.as_mut_ptr(),
          &mut raw_this,
          ptr::null_mut(),
        );
        debug_assert!(Status::from(status) == Status::Ok, "napi_get_cb_info failed");
      }

      let mut env = unsafe { Env::from_raw(raw_env) };
      let ctx = CallContext::new(&mut env, cb_info, raw_this, &raw_args, argc);
      #execute_js_function
    }
  };
  // Hand the output tokens back to the compiler
  RawStream::from(expanded)
}

#[cfg(feature = "compat-mode")]
#[proc_macro_attribute]
pub fn module_exports(_attr: RawStream, input: RawStream) -> RawStream {
  let input = parse_macro_input!(input as ItemFn);
  let mut js_fn = compat_macro::JsFunction::new();
  js_fn.fold_item_fn(input);
  let fn_block = js_fn.block;
  let fn_name = js_fn.name.unwrap();
  let signature = js_fn.signature_raw.unwrap();
  let args_len = js_fn.args.len();
  let call_expr = if args_len == 1 {
    quote! { #fn_name(exports) }
  } else if args_len == 2 {
    quote! { #fn_name(exports, env) }
  } else {
    panic!("Arguments length of #[module_exports] function must be 1 or 2");
  };

  let register = quote! {
    #[napi::bindgen_prelude::ctor]
    fn __napi__explicit_module_register() {
      unsafe fn register(raw_env: napi::sys::napi_env, raw_exports: napi::sys::napi_value) -> napi::Result<()> {
        use napi::{Env, JsObject, NapiValue};

        let env = Env::from_raw(raw_env);
        let exports = JsObject::from_raw_unchecked(raw_env, raw_exports);

        #call_expr
      }

      napi::bindgen_prelude::register_module_exports(register)
    }
  };

  (quote! {
    #[inline]
    #signature #(#fn_block)*

    #register
  })
  .into()
}