Async test function attribute

futures-macro/src/executor.rs

@@ -0,0 +1,27 @@
+use proc_macro::TokenStream;
+use quote::quote;
+
+pub(crate) fn test(_: TokenStream, item: TokenStream) -> TokenStream {
+    let mut input = syn::parse_macro_input!(item as syn::ItemFn);
+    let attrs = &input.attrs;
+    let vis = &input.vis;
+    let sig = &mut input.sig;
+    let body = &input.block;
+
+    if sig.asyncness.is_none() {
+        return syn::Error::new_spanned(sig.fn_token, "Only async functions are supported")
+            .to_compile_error()
+            .into();
+    }
+
+    sig.asyncness = None;
+
+    let gen = quote! {
+        #(#attrs)*
+        #vis #sig {
+            ::futures_test::__private::block_on(async move { #body })
+        }
+    };
+
+    gen.into()
+}

futures-macro/src/lib.rs

@@ -14,6 +14,7 @@ extern crate proc_macro;
 
 use proc_macro::TokenStream;
 
+mod executor;
 mod join;
 mod select;
 
@@ -44,3 +45,9 @@ pub fn select_internal(input: TokenStream) -> TokenStream {
 pub fn select_biased_internal(input: TokenStream) -> TokenStream {
     crate::select::select_biased(input)
 }
+
+/// The `test` attribute.
+#[proc_macro_attribute]
+pub fn test_internal(input: TokenStream, item: TokenStream) -> TokenStream {
+    crate::executor::test(input, item)
+}

futures-test/Cargo.toml

@@ -18,6 +18,7 @@ futures-io = { version = "0.3.14", path = "../futures-io", default-features = fa
 futures-util = { version = "=0.4.0-alpha.0", path = "../futures-util", default-features = false }
 futures-executor = { version = "=0.4.0-alpha.0", path = "../futures-executor", default-features = false }
 futures-sink = { version = "=0.4.0-alpha.0", path = "../futures-sink", default-features = false }
+futures-macro = { version = "=0.4.0-alpha.0", path = "../futures-macro", default-features = false }
 pin-utils = { version = "0.1.0", default-features = false }
 pin-project = "1.0.1"
 

futures-test/src/lib.rs

@@ -16,6 +16,7 @@ compile_error!(
 #[cfg(feature = "std")]
 pub mod __private {
     pub use futures_core::{future, stream, task};
+    pub use futures_executor::block_on;
     pub use std::{
         option::Option::{None, Some},
         pin::Pin,
@@ -49,3 +50,16 @@ pub mod io;
 mod assert_unmoved;
 mod interleave_pending;
 mod track_closed;
+
+/// Enables an `async` test function. The generated future will be run to completion with
+/// [`futures_executor::block_on`](futures_executor::block_on).
+///
+/// ```
+/// #[futures_test::test]
+/// async fn my_test() {
+///     let fut = async { true };
+///     assert!(fut.await);
+/// }
+/// ```
+#[cfg(feature = "std")]
+pub use futures_macro::test_internal as test;

futures-util/src/sink/mod.rs

@@ -243,7 +243,7 @@ pub trait SinkExt<Item>: Sink<Item> {
     /// This future will drive the stream to keep producing items until it is
     /// exhausted, sending each item to the sink. It will complete once both the
     /// stream is exhausted, the sink has received all items, and the sink has
-    /// been flushed. Note that the sink is **not** closed. If the stream produces 
+    /// been flushed. Note that the sink is **not** closed. If the stream produces
     /// an error, that error will be returned by this future without flushing the sink.
     ///
     /// Doing `sink.send_all(stream)` is roughly equivalent to