Drop Send in Command and Executor on Wasm

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()
+    }
+}

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()
+    }
+}