tokio: add `rt-current-thread` optional feature

- Adds a minimum `rt-current-thread` optional feature that exports
  `tokio::runtime::current_thread`.
- Adds a `macros` optional feature to enable the `#[tokio::main]` and
  `#[tokio::test]` attributes.
- Adjusts `#[tokio::main]` macro to select a runtime "automatically" if
  a specific strategy isn't specified. Allows using the macro with only
  the rt-current-thread feature.

1 files changed, 9 insertions, 1 deletions

diff --git a/tokio-macros/src/lib.rs b/tokio-macros/src/lib.rs
index 9a33c5fd..d8eedb02 100644
--- a/tokio-macros/src/lib.rs
+++ b/tokio-macros/src/lib.rs
@@ -49,6 +49,7 @@ pub fn main(args: TokenStream, item: TokenStream) -> TokenStream {
     enum RuntimeType {
         Single,
         Multi,
+        Auto,
     }
 
     let input = syn::parse_macro_input!(item as syn::ItemFn);
@@ -71,7 +72,7 @@ pub fn main(args: TokenStream, item: TokenStream) -> TokenStream {
             .into();
     }
 
-    let mut runtime = RuntimeType::Multi;
+    let mut runtime = RuntimeType::Auto;
 
     for arg in args {
         if let syn::NestedMeta::Meta(syn::Meta::Path(path)) = arg {
@@ -106,6 +107,13 @@ pub fn main(args: TokenStream, item: TokenStream) -> TokenStream {
                 rt.block_on(async { #body })
             }
         },
+        RuntimeType::Auto => quote! {
+            #(#attrs)*
+            fn #name() #ret {
+                let mut rt = tokio::runtime::__main::Runtime::new().unwrap();
+                rt.block_on(async { #body })
+            }
+        },
     };
 
     result.into()