Revamp TaskBuilder API

This patch consolidates and cleans up the task spawning APIs:

* Removes the problematic `future_result` method from `std::task::TaskBuilder`,
  and adds a `try_future` that both spawns the task and returns a future
  representing its eventual result (or failure).

* Removes the public `opts` field from `TaskBuilder`, instead adding appropriate
  builder methods to configure the task.

* Adds extension traits to libgreen and libnative that add methods to
  `TaskBuilder` for spawning the task as a green or native thread.

Previously, there was no way to benefit from the `TaskBuilder` functionality and
also set the scheduler to spawn within.

With this change, all task spawning scenarios are supported through the
`TaskBuilder` interface.

Closes #3725.

[breaking-change]

src/libgreen/lib.rs

@@ -159,16 +159,19 @@
 //!
 //! # Using a scheduler pool
 //!
+//! This library adds a `GreenTaskBuilder` trait that extends the methods
+//! available on `std::task::TaskBuilder` to allow spawning a green task,
+//! possibly pinned to a particular scheduler thread:
+//!
 //! ```rust
-//! use std::rt::task::TaskOpts;
-//! use green::{SchedPool, PoolConfig};
-//! use green::sched::{PinnedTask, TaskFromFriend};
+//! use std::task::TaskBuilder;
+//! use green::{SchedPool, PoolConfig, GreenTaskBuilder};
 //!
 //! let config = PoolConfig::new();
 //! let mut pool = SchedPool::new(config);
 //!
 //! // Spawn tasks into the pool of schedulers
-//! pool.spawn(TaskOpts::new(), proc() {
+//! TaskBuilder::new().green(&mut pool).spawn(proc() {
 //!     // this code is running inside the pool of schedulers
 //!
 //!     spawn(proc() {
@@ -181,12 +184,9 @@
 //! let mut handle = pool.spawn_sched();
 //!
 //! // Pin a task to the spawned scheduler
-//! let task = pool.task(TaskOpts::new(), proc() { /* ... */ });
-//! handle.send(PinnedTask(task));
-//!
-//! // Schedule a task on this new scheduler
-//! let task = pool.task(TaskOpts::new(), proc() { /* ... */ });
-//! handle.send(TaskFromFriend(task));
+//! TaskBuilder::new().green_pinned(&mut pool, &mut handle).spawn(proc() {
+//!     /* ... */
+//! });
 //!
 //! // Handles keep schedulers alive, so be sure to drop all handles before
 //! // destroying the sched pool
@@ -209,6 +209,8 @@
 // NB this does *not* include globs, please keep it that way.
 #![feature(macro_rules, phase)]
 #![allow(visible_private_types)]
+#![allow(deprecated)]
+#![feature(default_type_params)]
 
 #[cfg(test)] #[phase(plugin, link)] extern crate log;
 #[cfg(test)] extern crate rustuv;
@@ -224,8 +226,9 @@ use std::rt::task::TaskOpts;
 use std::rt;
 use std::sync::atomics::{SeqCst, AtomicUint, INIT_ATOMIC_UINT};
 use std::sync::deque;
+use std::task::{TaskBuilder, Spawner};
 
-use sched::{Shutdown, Scheduler, SchedHandle, TaskFromFriend, NewNeighbor};
+use sched::{Shutdown, Scheduler, SchedHandle, TaskFromFriend, PinnedTask, NewNeighbor};
 use sleeper_list::SleeperList;
 use stack::StackPool;
 use task::GreenTask;
@@ -444,6 +447,7 @@ impl SchedPool {
     /// This is useful to create a task which can then be sent to a specific
     /// scheduler created by `spawn_sched` (and possibly pin it to that
     /// scheduler).
+    #[deprecated = "use the green and green_pinned methods of GreenTaskBuilder instead"]
     pub fn task(&mut self, opts: TaskOpts, f: proc():Send) -> Box<GreenTask> {
         GreenTask::configure(&mut self.stack_pool, opts, f)
     }
@@ -454,6 +458,7 @@ impl SchedPool {
     /// New tasks are spawned in a round-robin fashion to the schedulers in this
     /// pool, but tasks can certainly migrate among schedulers once they're in
     /// the pool.
+    #[deprecated = "use the green and green_pinned methods of GreenTaskBuilder instead"]
     pub fn spawn(&mut self, opts: TaskOpts, f: proc():Send) {
         let task = self.task(opts, f);
 
@@ -563,3 +568,54 @@ impl Drop for SchedPool {
         }
     }
 }
+
+/// A spawner for green tasks
+pub struct GreenSpawner<'a>{
+    pool: &'a mut SchedPool,
+    handle: Option<&'a mut SchedHandle>
+}
+
+impl<'a> Spawner for GreenSpawner<'a> {
+    #[inline]
+    fn spawn(self, opts: TaskOpts, f: proc():Send) {
+        let GreenSpawner { pool, handle } = self;
+        match handle {
+            None    => pool.spawn(opts, f),
+            Some(h) => h.send(PinnedTask(pool.task(opts, f)))
+        }
+    }
+}
+
+/// An extension trait adding `green` configuration methods to `TaskBuilder`.
+pub trait GreenTaskBuilder {
+    fn green<'a>(self, &'a mut SchedPool) -> TaskBuilder<GreenSpawner<'a>>;
+    fn green_pinned<'a>(self, &'a mut SchedPool, &'a mut SchedHandle)
+                        -> TaskBuilder<GreenSpawner<'a>>;
+}
+
+impl<S: Spawner> GreenTaskBuilder for TaskBuilder<S> {
+    fn green<'a>(self, pool: &'a mut SchedPool) -> TaskBuilder<GreenSpawner<'a>> {
+        self.spawner(GreenSpawner {pool: pool, handle: None})
+    }
+
+    fn green_pinned<'a>(self, pool: &'a mut SchedPool, handle: &'a mut SchedHandle)
+                        -> TaskBuilder<GreenSpawner<'a>> {
+        self.spawner(GreenSpawner {pool: pool, handle: Some(handle)})
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use std::task::TaskBuilder;
+    use super::{SchedPool, PoolConfig, GreenTaskBuilder};
+
+    #[test]
+    fn test_green_builder() {
+        let mut pool = SchedPool::new(PoolConfig::new());
+        let res = TaskBuilder::new().green(&mut pool).try(proc() {
+            "Success!".to_string()
+        });
+        assert_eq!(res.ok().unwrap(), "Success!".to_string());
+        pool.shutdown();
+    }
+}

src/libnative/lib.rs

@@ -32,10 +32,13 @@
 //! ```rust
 //! extern crate native;
 //!
+//! use std::task::TaskBuilder;
+//! use native::NativeTaskBuilder;
+//!
 //! fn main() {
 //!     // We're not sure whether this main function is run in 1:1 or M:N mode.
 //!
-//!     native::task::spawn(proc() {
+//!     TaskBuilder::new().native().spawn(proc() {
 //!         // this code is guaranteed to be run on a native thread
 //!     });
 //! }
@@ -50,7 +53,8 @@
        html_root_url = "http://doc.rust-lang.org/")]
 #![deny(unused_result, unused_must_use)]
 #![allow(non_camel_case_types)]
-#![feature(macro_rules)]
+#![allow(deprecated)]
+#![feature(default_type_params)]
 
 // NB this crate explicitly does *not* allow glob imports, please seriously
 //    consider whether they're needed before adding that feature here (the
@@ -65,6 +69,8 @@ use std::os;
 use std::rt;
 use std::str;
 
+pub use task::NativeTaskBuilder;
+
 pub mod io;
 pub mod task;
 

src/libnative/task.rs

@@ -27,6 +27,7 @@ use std::rt;
 
 use io;
 use task;
+use std::task::{TaskBuilder, Spawner};
 
 /// Creates a new Task which is ready to execute as a 1:1 task.
 pub fn new(stack_bounds: (uint, uint)) -> Box<Task> {
@@ -48,12 +49,14 @@ fn ops() -> Box<Ops> {
 }
 
 /// Spawns a function with the default configuration
+#[deprecated = "use the native method of NativeTaskBuilder instead"]
 pub fn spawn(f: proc():Send) {
     spawn_opts(TaskOpts { name: None, stack_size: None, on_exit: None }, f)
 }
 
 /// Spawns a new task given the configuration options and a procedure to run
 /// inside the task.
+#[deprecated = "use the native method of NativeTaskBuilder instead"]
 pub fn spawn_opts(opts: TaskOpts, f: proc():Send) {
     let TaskOpts { name, stack_size, on_exit } = opts;
 
@@ -95,6 +98,26 @@ pub fn spawn_opts(opts: TaskOpts, f: proc():Send) {
     })
 }
 
+/// A spawner for native tasks
+pub struct NativeSpawner;
+
+impl Spawner for NativeSpawner {
+    fn spawn(self, opts: TaskOpts, f: proc():Send) {
+        spawn_opts(opts, f)
+    }
+}
+
+/// An extension trait adding a `native` configuration method to `TaskBuilder`.
+pub trait NativeTaskBuilder {
+    fn native(self) -> TaskBuilder<NativeSpawner>;
+}
+
+impl<S: Spawner> NativeTaskBuilder for TaskBuilder<S> {
+    fn native(self) -> TaskBuilder<NativeSpawner> {
+        self.spawner(NativeSpawner)
+    }
+}
+
 // This structure is the glue between channels and the 1:1 scheduling mode. This
 // structure is allocated once per task.
 struct Ops {
@@ -259,7 +282,8 @@ mod tests {
     use std::rt::local::Local;
     use std::rt::task::{Task, TaskOpts};
     use std::task;
-    use super::{spawn, spawn_opts, Ops};
+    use std::task::TaskBuilder;
+    use super::{spawn, spawn_opts, Ops, NativeTaskBuilder};
 
     #[test]
     fn smoke() {
@@ -347,4 +371,12 @@ mod tests {
         });
         rx.recv();
     }
+
+    #[test]
+    fn test_native_builder() {
+        let res = TaskBuilder::new().native().try(proc() {
+            "Success!".to_string()
+        });
+        assert_eq!(res.ok().unwrap(), "Success!".to_string());
+    }
 }