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#[macro_use]
extern crate quote;
use proc_macro::TokenStream;
use syn::spanned::Spanned;
use syn::{parse, ImplItemMethod, ItemImpl, ItemTrait, Token};
fn add_async_trait(mut parsed: ItemTrait) -> TokenStream {
let output = quote! {
#[cfg(all(not(target_arch = "wasm32"), not(feature = "async-interface")))]
#parsed
};
for mut item in &mut parsed.items {
if let syn::TraitItem::Method(m) = &mut item {
m.sig.asyncness = Some(Token![async](m.span()));
}
}
let output = quote! {
#output
#[cfg(any(target_arch = "wasm32", feature = "async-interface"))]
#[async_trait(?Send)]
#parsed
};
output.into()
}
fn add_async_method(mut parsed: ImplItemMethod) -> TokenStream {
let output = quote! {
#[cfg(all(not(target_arch = "wasm32"), not(feature = "async-interface")))]
#parsed
};
parsed.sig.asyncness = Some(Token![async](parsed.span()));
let output = quote! {
#output
#[cfg(any(target_arch = "wasm32", feature = "async-interface"))]
#parsed
};
output.into()
}
fn add_async_impl_trait(mut parsed: ItemImpl) -> TokenStream {
let output = quote! {
#[cfg(all(not(target_arch = "wasm32"), not(feature = "async-interface")))]
#parsed
};
for mut item in &mut parsed.items {
if let syn::ImplItem::Method(m) = &mut item {
m.sig.asyncness = Some(Token![async](m.span()));
}
}
let output = quote! {
#output
#[cfg(any(target_arch = "wasm32", feature = "async-interface"))]
#[async_trait(?Send)]
#parsed
};
output.into()
}
#[proc_macro_attribute]
pub fn maybe_async(_attr: TokenStream, item: TokenStream) -> TokenStream {
if let Ok(parsed) = parse(item.clone()) {
add_async_trait(parsed)
} else if let Ok(parsed) = parse(item.clone()) {
add_async_method(parsed)
} else if let Ok(parsed) = parse(item) {
add_async_impl_trait(parsed)
} else {
(quote! {
compile_error!("#[maybe_async] can only be used on methods, trait or trait impl blocks")
})
.into()
}
}
#[proc_macro]
pub fn maybe_await(expr: TokenStream) -> TokenStream {
let expr: proc_macro2::TokenStream = expr.into();
let quoted = quote! {
{
#[cfg(all(not(target_arch = "wasm32"), not(feature = "async-interface")))]
{
#expr
}
#[cfg(any(target_arch = "wasm32", feature = "async-interface"))]
{
#expr.await
}
}
};
quoted.into()
}
#[proc_macro]
pub fn await_or_block(expr: TokenStream) -> TokenStream {
let expr: proc_macro2::TokenStream = expr.into();
let quoted = quote! {
{
#[cfg(all(not(target_arch = "wasm32"), not(feature = "async-interface")))]
{
tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap().block_on(#expr)
}
#[cfg(any(target_arch = "wasm32", feature = "async-interface"))]
{
#expr.await
}
}
};
quoted.into()
}