Async/await polish (#1058)

A general refresh of Tokio's experimental async / await support.

tokio-macros/src/lib.rs

@@ -0,0 +1,79 @@
+#![cfg(feature = "async-await-preview")]
+
+extern crate proc_macro;
+
+use proc_macro::TokenStream;
+use quote::{quote, quote_spanned};
+use syn::spanned::Spanned;
+
+/// Define the program entry point
+///
+/// # Examples
+///
+/// ```
+/// #[tokio::main]
+/// async fn main() {
+///     println!("Hello world");
+/// }
+#[proc_macro_attribute]
+pub fn main(_attr: TokenStream, item: TokenStream) -> TokenStream {
+    let input = syn::parse_macro_input!(item as syn::ItemFn);
+
+    let ret = &input.decl.output;
+    let name = &input.ident;
+    let body = &input.block;
+
+    if input.asyncness.is_none() {
+        let tokens = quote_spanned! { input.span() =>
+          compile_error!("the async keyword is missing from the function declaration");
+        };
+
+        return TokenStream::from(tokens);
+    }
+
+    let result = quote! {
+        fn #name() #ret {
+            let mut rt = tokio::runtime::Runtime::new().unwrap();
+            rt.block_on_async(async { #body })
+        }
+    };
+
+    result.into()
+}
+
+/// Define a Tokio aware unit test
+///
+/// # Examples
+///
+/// ```
+/// #[tokio::test]
+/// async fn my_test() {
+///     assert!(true);
+/// }
+/// ```
+#[proc_macro_attribute]
+pub fn test(_attr: TokenStream, item: TokenStream) -> TokenStream {
+    let input = syn::parse_macro_input!(item as syn::ItemFn);
+
+    let ret = &input.decl.output;
+    let name = &input.ident;
+    let body = &input.block;
+
+    if input.asyncness.is_none() {
+        let tokens = quote_spanned! { input.span() =>
+          compile_error!("the async keyword is missing from the function declaration");
+        };
+
+        return TokenStream::from(tokens);
+    }
+
+    let result = quote! {
+        #[test]
+        fn #name() #ret {
+            let mut rt = tokio::runtime::current_thread::Runtime::new().unwrap();
+            rt.block_on_async(async { #body })
+        }
+    };
+
+    result.into()
+}