Drop `Send` in `Command` and `Executor` on Wasm

7 files changed, 227 insertions, 105 deletions

diff --git a/futures/src/command.rs b/futures/src/command.rs
index e7885fb8..26f58fde 100644
--- a/futures/src/command.rs
+++ b/futures/src/command.rs
@@ -1,100 +1,11 @@
-use futures::future::{BoxFuture, Future, FutureExt};
+#[cfg(not(target_arch = "wasm32"))]
+mod native;
 
-/// A collection of async operations.
-///
-/// You should be able to turn a future easily into a [`Command`], either by
-/// using the `From` trait or [`Command::perform`].
-///
-/// [`Command`]: struct.Command.html
-pub struct Command<T> {
-    futures: Vec<BoxFuture<'static, T>>,
-}
+#[cfg(not(target_arch = "wasm32"))]
+pub use native::Command;
 
-impl<T> Command<T> {
-    /// Creates an empty [`Command`].
-    ///
-    /// In other words, a [`Command`] that does nothing.
-    ///
-    /// [`Command`]: struct.Command.html
-    pub fn none() -> Self {
-        Self {
-            futures: Vec::new(),
-        }
-    }
+#[cfg(target_arch = "wasm32")]
+mod web;
 
-    /// Creates a [`Command`] that performs the action of the given future.
-    ///
-    /// [`Command`]: struct.Command.html
-    pub fn perform<A>(
-        future: impl Future<Output = T> + 'static + Send,
-        f: impl Fn(T) -> A + 'static + Send,
-    ) -> Command<A> {
-        Command {
-            futures: vec![future.map(f).boxed()],
-        }
-    }
-
-    /// Applies a transformation to the result of a [`Command`].
-    ///
-    /// [`Command`]: struct.Command.html
-    pub fn map<A>(
-        mut self,
-        f: impl Fn(T) -> A + 'static + Send + Sync,
-    ) -> Command<A>
-    where
-        T: 'static,
-    {
-        let f = std::sync::Arc::new(f);
-
-        Command {
-            futures: self
-                .futures
-                .drain(..)
-                .map(|future| {
-                    let f = f.clone();
-
-                    future.map(move |result| f(result)).boxed()
-                })
-                .collect(),
-        }
-    }
-
-    /// Creates a [`Command`] that performs the actions of all the given
-    /// commands.
-    ///
-    /// Once this command is run, all the commands will be exectued at once.
-    ///
-    /// [`Command`]: struct.Command.html
-    pub fn batch(commands: impl IntoIterator<Item = Command<T>>) -> Self {
-        Self {
-            futures: commands
-                .into_iter()
-                .flat_map(|command| command.futures)
-                .collect(),
-        }
-    }
-
-    /// Converts a [`Command`] into its underlying list of futures.
-    ///
-    /// [`Command`]: struct.Command.html
-    pub fn futures(self) -> Vec<BoxFuture<'static, T>> {
-        self.futures
-    }
-}
-
-impl<T, A> From<A> for Command<T>
-where
-    A: Future<Output = T> + 'static + Send,
-{
-    fn from(future: A) -> Self {
-        Self {
-            futures: vec![future.boxed()],
-        }
-    }
-}
-
-impl<T> std::fmt::Debug for Command<T> {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        f.debug_struct("Command").finish()
-    }
-}
+#[cfg(target_arch = "wasm32")]
+pub use web::Command;
diff --git a/futures/src/command/native.rs b/futures/src/command/native.rs
new file mode 100644
index 00000000..38cb4e06
--- /dev/null
+++ b/futures/src/command/native.rs
@@ -0,0 +1,100 @@
+use futures::future::{BoxFuture, Future, FutureExt};
+
+/// A collection of async operations.
+///
+/// You should be able to turn a future easily into a [`Command`], either by
+/// using the `From` trait or [`Command::perform`].
+///
+/// [`Command`]: struct.Command.html
+pub struct Command<T> {
+    futures: Vec<BoxFuture<'static, T>>,
+}
+
+impl<T> Command<T> {
+    /// Creates an empty [`Command`].
+    ///
+    /// In other words, a [`Command`] that does nothing.
+    ///
+    /// [`Command`]: struct.Command.html
+    pub fn none() -> Self {
+        Self {
+            futures: Vec::new(),
+        }
+    }
+
+    /// Creates a [`Command`] that performs the action of the given future.
+    ///
+    /// [`Command`]: struct.Command.html
+    pub fn perform<A>(
+        future: impl Future<Output = T> + 'static + Send,
+        f: impl Fn(T) -> A + 'static + Send,
+    ) -> Command<A> {
+        Command {
+            futures: vec![future.map(f).boxed()],
+        }
+    }
+
+    /// Applies a transformation to the result of a [`Command`].
+    ///
+    /// [`Command`]: struct.Command.html
+    pub fn map<A>(
+        mut self,
+        f: impl Fn(T) -> A + 'static + Send + Sync,
+    ) -> Command<A>
+    where
+        T: 'static,
+    {
+        let f = std::sync::Arc::new(f);
+
+        Command {
+            futures: self
+                .futures
+                .drain(..)
+                .map(|future| {
+                    let f = f.clone();
+
+                    future.map(move |result| f(result)).boxed()
+                })
+                .collect(),
+        }
+    }
+
+    /// Creates a [`Command`] that performs the actions of all the given
+    /// commands.
+    ///
+    /// Once this command is run, all the commands will be executed at once.
+    ///
+    /// [`Command`]: struct.Command.html
+    pub fn batch(commands: impl IntoIterator<Item = Command<T>>) -> Self {
+        Self {
+            futures: commands
+                .into_iter()
+                .flat_map(|command| command.futures)
+                .collect(),
+        }
+    }
+
+    /// Converts a [`Command`] into its underlying list of futures.
+    ///
+    /// [`Command`]: struct.Command.html
+    pub fn futures(self) -> Vec<BoxFuture<'static, T>> {
+        self.futures
+    }
+}
+
+impl<T, A> From<A> for Command<T>
+where
+    A: Future<Output = T> + 'static + Send,
+{
+    fn from(future: A) -> Self {
+        Self {
+            futures: vec![future.boxed()],
+        }
+    }
+}
+
+impl<T> std::fmt::Debug for Command<T> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Command").finish()
+    }
+}
diff --git a/futures/src/command/web.rs b/futures/src/command/web.rs
new file mode 100644
index 00000000..11b46b90
--- /dev/null
+++ b/futures/src/command/web.rs
@@ -0,0 +1,101 @@
+use futures::future::{Future, FutureExt};
+use std::pin::Pin;
+
+/// A collection of async operations.
+///
+/// You should be able to turn a future easily into a [`Command`], either by
+/// using the `From` trait or [`Command::perform`].
+///
+/// [`Command`]: struct.Command.html
+pub struct Command<T> {
+    futures: Vec<Pin<Box<dyn Future<Output = T> + 'static>>>,
+}
+
+impl<T> Command<T> {
+    /// Creates an empty [`Command`].
+    ///
+    /// In other words, a [`Command`] that does nothing.
+    ///
+    /// [`Command`]: struct.Command.html
+    pub fn none() -> Self {
+        Self {
+            futures: Vec::new(),
+        }
+    }
+
+    /// Creates a [`Command`] that performs the action of the given future.
+    ///
+    /// [`Command`]: struct.Command.html
+    pub fn perform<A>(
+        future: impl Future<Output = T> + 'static,
+        f: impl Fn(T) -> A + 'static,
+    ) -> Command<A> {
+        Command {
+            futures: vec![future.map(f).boxed_local()],
+        }
+    }
+
+    /// Applies a transformation to the result of a [`Command`].
+    ///
+    /// [`Command`]: struct.Command.html
+    pub fn map<A>(
+        mut self,
+        f: impl Fn(T) -> A + 'static + Send + Sync + Unpin,
+    ) -> Command<A>
+    where
+        T: 'static,
+    {
+        let f = std::sync::Arc::new(f);
+
+        Command {
+            futures: self
+                .futures
+                .drain(..)
+                .map(|future| {
+                    let f = f.clone();
+
+                    future.map(move |result| f(result)).boxed_local()
+                })
+                .collect(),
+        }
+    }
+
+    /// Creates a [`Command`] that performs the actions of all the given
+    /// commands.
+    ///
+    /// Once this command is run, all the commands will be executed at once.
+    ///
+    /// [`Command`]: struct.Command.html
+    pub fn batch(commands: impl IntoIterator<Item = Command<T>>) -> Self {
+        Self {
+            futures: commands
+                .into_iter()
+                .flat_map(|command| command.futures)
+                .collect(),
+        }
+    }
+
+    /// Converts a [`Command`] into its underlying list of futures.
+    ///
+    /// [`Command`]: struct.Command.html
+    pub fn futures(self) -> Vec<Pin<Box<dyn Future<Output = T> + 'static>>> {
+        self.futures
+    }
+}
+
+impl<T, A> From<A> for Command<T>
+where
+    A: Future<Output = T> + 'static,
+{
+    fn from(future: A) -> Self {
+        Self {
+            futures: vec![future.boxed_local()],
+        }
+    }
+}
+
+impl<T> std::fmt::Debug for Command<T> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Command").finish()
+    }
+}
diff --git a/futures/src/executor.rs b/futures/src/executor.rs
index 2a5281af..5378c0b3 100644
--- a/futures/src/executor.rs
+++ b/futures/src/executor.rs
@@ -1,7 +1,7 @@
 //! Choose your preferred executor to power a runtime.
 mod null;
 
-#[cfg(feature = "thread-pool")]
+#[cfg(all(not(target_arch = "wasm32"), feature = "thread-pool"))]
 mod thread_pool;
 
 #[cfg(all(not(target_arch = "wasm32"), feature = "tokio"))]
@@ -15,7 +15,7 @@ mod wasm_bindgen;
 
 pub use null::Null;
 
-#[cfg(feature = "thread-pool")]
+#[cfg(all(not(target_arch = "wasm32"), feature = "thread-pool"))]
 pub use thread_pool::ThreadPool;
 
 #[cfg(all(not(target_arch = "wasm32"), feature = "tokio"))]
@@ -41,8 +41,15 @@ pub trait Executor: Sized {
     /// Spawns a future in the [`Executor`].
     ///
     /// [`Executor`]: trait.Executor.html
+    #[cfg(not(target_arch = "wasm32"))]
     fn spawn(&self, future: impl Future<Output = ()> + Send + 'static);
 
+    /// Spawns a local future in the [`Executor`].
+    ///
+    /// [`Executor`]: trait.Executor.html
+    #[cfg(target_arch = "wasm32")]
+    fn spawn(&self, future: impl Future<Output = ()> + 'static);
+
     /// Runs the given closure inside the [`Executor`].
     ///
     /// Some executors, like `tokio`, require some global state to be in place
diff --git a/futures/src/executor/null.rs b/futures/src/executor/null.rs
index 6d5cf982..65e2e2df 100644
--- a/futures/src/executor/null.rs
+++ b/futures/src/executor/null.rs
@@ -11,5 +11,9 @@ impl Executor for Null {
         Ok(Self)
     }
 
+    #[cfg(not(target_arch = "wasm32"))]
     fn spawn(&self, _future: impl Future<Output = ()> + Send + 'static) {}
+
+    #[cfg(target_arch = "wasm32")]
+    fn spawn(&self, _future: impl Future<Output = ()> + 'static) {}
 }
diff --git a/futures/src/executor/wasm_bindgen.rs b/futures/src/executor/wasm_bindgen.rs
index 69b7c7e2..94d694c8 100644
--- a/futures/src/executor/wasm_bindgen.rs
+++ b/futures/src/executor/wasm_bindgen.rs
@@ -9,10 +9,7 @@ impl Executor for WasmBindgen {
         Ok(Self)
     }
 
-    fn spawn(
-        &self,
-        future: impl futures::Future<Output = ()> + Send + 'static,
-    ) {
+    fn spawn(&self, future: impl futures::Future<Output = ()> + 'static) {
         wasm_bindgen_futures::spawn_local(future);
     }
 }
diff --git a/futures/src/runtime.rs b/futures/src/runtime.rs
index 3be45a26..ede529dc 100644
--- a/futures/src/runtime.rs
+++ b/futures/src/runtime.rs
@@ -73,11 +73,13 @@ where
         for future in futures {
             let mut sender = self.sender.clone();
 
-            self.executor.spawn(future.then(|message| async move {
+            let future = future.then(|message| async move {
                 let _ = sender.send(message).await;
 
                 ()
-            }));
+            });
+
+            self.executor.spawn(future);
         }
     }