matrix-rust-sdk

// Copyright 2024 The Matrix.org Foundation C.I.C.

//

// Licensed under the Apache License, Version 2.0 (the "License");

// you may not use this file except in compliance with the License.

// You may obtain a copy of the License at

//

//     http://www.apache.org/licenses/LICENSE-2.0

//

// Unless required by applicable law or agreed to in writing, software

// distributed under the License is distributed on an "AS IS" BASIS,

// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

// See the License for the specific language governing permissions and

// limitations under the License.

use proc_macro::TokenStream;

use quote::quote;

use syn::{ImplItem, Item, TraitItem};

/// Attribute to specify the async runtime parameter for the `uniffi`

/// export macros if there any `async fn`s in the input.

#[proc_macro_attribute]

pub fn export(attr: TokenStream, item: TokenStream) -> TokenStream {

    let has_async_fn = |item| {

        if let Item::Fn(fun) = &item {

            if fun.sig.asyncness.is_some() {

                return true;

            }

        } else if let Item::Impl(blk) = &item {

            for item in &blk.items {

                if let ImplItem::Fn(fun) = item

                    && fun.sig.asyncness.is_some()

                {

                    return true;

                }

            }

        } else if let Item::Trait(blk) = &item {

            for item in &blk.items {

                if let TraitItem::Fn(fun) = item

                    && fun.sig.asyncness.is_some()

                {

                    return true;

                }

            }

        }

        false

    };

    let attr2 = proc_macro2::TokenStream::from(attr);

    let item2 = proc_macro2::TokenStream::from(item.clone());

    let res = match syn::parse(item) {

        Ok(item) => match has_async_fn(item) {

            true => {

                quote! {

                  #[cfg_attr(target_family = "wasm", uniffi::export(#attr2))]

                  #[cfg_attr(not(target_family = "wasm"), uniffi::export(async_runtime = "tokio", #attr2))]

                }

            }

            false => quote! { #[uniffi::export(#attr2)] },

        },

        Err(e) => e.into_compile_error(),

    };

    quote! {

        #res

        #item2

    }

    .into()

}