Simultaneous futures compat (#172)

This patch adds opt-in support for futures 0.2.

tokio-executor/src/enter.rs

@@ -2,6 +2,9 @@ use std::prelude::v1::*;
 use std::cell::Cell;
 use std::fmt;
 
+#[cfg(feature = "unstable-futures")]
+use futures2;
+
 thread_local!(static ENTERED: Cell<bool> = Cell::new(false));
 
 /// Represents an executor context.
@@ -10,6 +13,9 @@ thread_local!(static ENTERED: Cell<bool> = Cell::new(false));
 pub struct Enter {
     on_exit: Vec<Box<Callback>>,
     permanent: bool,
+
+    #[cfg(feature = "unstable-futures")]
+    _enter2: futures2::executor::Enter,
 }
 
 /// An error returned by `enter` if an execution scope has already been
@@ -40,6 +46,9 @@ pub fn enter() -> Result<Enter, EnterError> {
             Ok(Enter {
                 on_exit: Vec::new(),
                 permanent: false,
+
+                #[cfg(feature = "unstable-futures")]
+                _enter2: futures2::executor::enter().unwrap(),
             })
         }
     })

tokio-executor/src/global.rs

@@ -6,6 +6,9 @@ use std::cell::Cell;
 use std::marker::PhantomData;
 use std::rc::Rc;
 
+#[cfg(feature = "unstable-futures")]
+use futures2;
+
 /// Executes futures on the default executor for the current execution context.
 ///
 /// `DefaultExecutor` implements `Executor` and can be used to spawn futures
@@ -59,6 +62,23 @@ impl super::Executor for DefaultExecutor {
             }
         })
     }
+
+    #[cfg(feature = "unstable-futures")]
+    fn spawn2(&mut self, future: Box<futures2::Future<Item = (), Error = futures2::Never> + Send>)
+             -> Result<(), futures2::executor::SpawnError>
+    {
+        EXECUTOR.with(|current_executor| {
+            match current_executor.get() {
+                Some(executor) => {
+                    let executor = unsafe { &mut *executor };
+                    executor.spawn2(future)
+                }
+                None => {
+                    Err(futures2::executor::SpawnError::shutdown())
+                }
+            }
+        })
+    }
 }
 
 // ===== global spawn fns =====
@@ -109,6 +129,15 @@ pub fn spawn<T>(future: T)
         .unwrap()
 }
 
+/// Like `spawn` but compatible with futures 0.2
+#[cfg(feature = "unstable-futures")]
+pub fn spawn2<T>(future: T)
+    where T: futures2::Future<Item = (), Error = futures2::Never> + Send + 'static,
+{
+    DefaultExecutor::current().spawn2(Box::new(future))
+        .unwrap()
+}
+
 /// Set the default executor for the duration of the closure
 ///
 /// # Panics

tokio-executor/src/lib.rs

@@ -35,6 +35,9 @@
 
 extern crate futures;
 
+#[cfg(feature = "unstable-futures")]
+extern crate futures2;
+
 mod enter;
 mod global;
 pub mod park;
@@ -42,6 +45,9 @@ pub mod park;
 pub use enter::{enter, Enter, EnterError};
 pub use global::{spawn, with_default, DefaultExecutor};
 
+#[cfg(feature = "unstable-futures")]
+pub use global::spawn2;
+
 use futures::Future;
 
 /// A value that executes futures.
@@ -129,7 +135,12 @@ pub trait Executor {
     /// # fn main() {}
     /// ```
     fn spawn(&mut self, future: Box<Future<Item = (), Error = ()> + Send>)
-        -> Result<(), SpawnError>;
+             -> Result<(), SpawnError>;
+
+    /// Like `spawn`, but compatible with futures 0.2
+    #[cfg(feature = "unstable-futures")]
+    fn spawn2(&mut self, future: Box<futures2::Future<Item = (), Error = futures2::Never> + Send>)
+             -> Result<(), futures2::executor::SpawnError>;
 
     /// Provides a best effort **hint** to whether or not `spawn` will succeed.
     ///