Support an equivalent of Trusted<T> for Rc<Promise> objects named TrustedPromise.

components/script/dom/bindings/refcounted.rs

@@ -26,6 +26,7 @@ use core::nonzero::NonZero;
 use dom::bindings::js::Root;
 use dom::bindings::reflector::{Reflectable, Reflector};
 use dom::bindings::trace::trace_reflector;
+use dom::promise::Promise;
 use js::jsapi::JSTracer;
 use libc;
 use std::cell::RefCell;
@@ -34,6 +35,7 @@ use std::collections::hash_map::HashMap;
 use std::hash::Hash;
 use std::marker::PhantomData;
 use std::os;
+use std::rc::Rc;
 use std::sync::{Arc, Weak};
 
 
@@ -58,6 +60,63 @@ impl TrustedReference {
     }
 }
 
+/// A safe wrapper around a DOM Promise object that can be shared among threads for use
+/// in asynchronous operations. The underlying DOM object is guaranteed to live at least
+/// as long as the last outstanding `TrustedPromise` instance. These values cannot be cloned,
+/// only created from existing Rc<Promise> values.
+pub struct TrustedPromise {
+    dom_object: *const Promise,
+    owner_thread: *const libc::c_void,
+}
+
+unsafe impl Send for TrustedPromise {}
+
+impl TrustedPromise {
+    /// Create a new `TrustedPromise` instance from an existing DOM object. The object will
+    /// be prevented from being GCed for the duration of the resulting `TrustedPromise` object's
+    /// lifetime.
+    #[allow(unrooted_must_root)]
+    pub fn new(promise: Rc<Promise>) -> TrustedPromise {
+        LIVE_REFERENCES.with(|ref r| {
+            let r = r.borrow();
+            let live_references = r.as_ref().unwrap();
+            let ptr = &*promise as *const Promise;
+            live_references.addref_promise(promise);
+            TrustedPromise {
+                dom_object: ptr,
+                owner_thread: (&*live_references) as *const _ as *const libc::c_void,
+            }
+        })
+    }
+
+    /// Obtain a usable DOM Promise from a pinned `TrustedPromise` value. Fails if used on
+    /// a different thread than the original value from which this `TrustedPromise` was
+    /// obtained.
+    #[allow(unrooted_must_root)]
+    pub fn root(self) -> Rc<Promise> {
+        LIVE_REFERENCES.with(|ref r| {
+            let r = r.borrow();
+            let live_references = r.as_ref().unwrap();
+            assert!(self.owner_thread == (&*live_references) as *const _ as *const libc::c_void);
+            // Borrow-check error requires the redundant `let promise = ...; promise` here.
+            let promise = match live_references.promise_table.borrow_mut().entry(self.dom_object) {
+                Occupied(mut entry) => {
+                    let promise = {
+                        let promises = entry.get_mut();
+                        promises.pop().expect("rooted promise list unexpectedly empty")
+                    };
+                    if entry.get().is_empty() {
+                        entry.remove();
+                    }
+                    promise
+                }
+                Vacant(_) => unreachable!(),
+            };
+            promise
+        })
+    }
+}
+
 /// A safe wrapper around a raw pointer to a DOM object that can be
 /// shared among threads for use in asynchronous operations. The underlying
 /// DOM object is guaranteed to live at least as long as the last outstanding
@@ -117,9 +176,11 @@ impl<T: Reflectable> Clone for Trusted<T> {
 
 /// The set of live, pinned DOM objects that are currently prevented
 /// from being garbage collected due to outstanding references.
+#[allow(unrooted_must_root)]
 pub struct LiveDOMReferences {
     // keyed on pointer to Rust DOM object
-    table: RefCell<HashMap<*const libc::c_void, Weak<TrustedReference>>>,
+    reflectable_table: RefCell<HashMap<*const libc::c_void, Weak<TrustedReference>>>,
+    promise_table: RefCell<HashMap<*const Promise, Vec<Rc<Promise>>>>,
 }
 
 impl LiveDOMReferences {
@@ -127,13 +188,20 @@ impl LiveDOMReferences {
     pub fn initialize() {
         LIVE_REFERENCES.with(|ref r| {
             *r.borrow_mut() = Some(LiveDOMReferences {
-                table: RefCell::new(HashMap::new()),
+                reflectable_table: RefCell::new(HashMap::new()),
+                promise_table: RefCell::new(HashMap::new()),
             })
         });
     }
 
+    #[allow(unrooted_must_root)]
+    fn addref_promise(&self, promise: Rc<Promise>) {
+        let mut table = self.promise_table.borrow_mut();
+        table.entry(&*promise).or_insert(vec![]).push(promise)
+    }
+
     fn addref<T: Reflectable>(&self, ptr: *const T) -> Arc<TrustedReference> {
-        let mut table = self.table.borrow_mut();
+        let mut table = self.reflectable_table.borrow_mut();
         let capacity = table.capacity();
         let len = table.len();
         if (0 < capacity) && (capacity <= len) {
@@ -173,17 +241,27 @@ fn remove_nulls<K: Eq + Hash + Clone, V> (table: &mut HashMap<K, Weak<V>>) {
 }
 
 /// A JSTraceDataOp for tracing reflectors held in LIVE_REFERENCES
+#[allow(unrooted_must_root)]
 pub unsafe extern "C" fn trace_refcounted_objects(tracer: *mut JSTracer,
                                                   _data: *mut os::raw::c_void) {
     info!("tracing live refcounted references");
     LIVE_REFERENCES.with(|ref r| {
         let r = r.borrow();
         let live_references = r.as_ref().unwrap();
-        let mut table = live_references.table.borrow_mut();
+        {
+            let mut table = live_references.reflectable_table.borrow_mut();
             remove_nulls(&mut table);
             for obj in table.keys() {
                 let reflectable = &*(*obj as *const Reflector);
                 trace_reflector(tracer, "refcounted", reflectable);
             }
+        }
+
+        {
+            let table = live_references.promise_table.borrow_mut();
+            for promise in table.keys() {
+                trace_reflector(tracer, "refcounted", (**promise).reflector());
+            }
+        }
     });
 }

components/script/dom/bindings/trace.rs

@@ -36,7 +36,7 @@ use devtools_traits::CSSError;
 use devtools_traits::WorkerId;
 use dom::abstractworker::SharedRt;
 use dom::bindings::js::{JS, Root};
-use dom::bindings::refcounted::Trusted;
+use dom::bindings::refcounted::{Trusted, TrustedPromise};
 use dom::bindings::reflector::{Reflectable, Reflector};
 use dom::bindings::str::{DOMString, USVString};
 use dom::bindings::utils::WindowProxyHandler;
@@ -303,6 +303,7 @@ no_jsmanaged_fields!(Metadata);
 no_jsmanaged_fields!(NetworkError);
 no_jsmanaged_fields!(Atom, Namespace, QualName);
 no_jsmanaged_fields!(Trusted<T: Reflectable>);
+no_jsmanaged_fields!(TrustedPromise);
 no_jsmanaged_fields!(PropertyDeclarationBlock);
 no_jsmanaged_fields!(HashSet<T>);
 // These three are interdependent, if you plan to put jsmanaged data

components/script/dom/promise.rs

@@ -79,6 +79,14 @@ impl Promise {
         }
     }
 
+    #[allow(unsafe_code, unrooted_must_root)]
+    pub fn duplicate(&self) -> Rc<Promise> {
+        let cx = self.global().r().get_cx();
+        unsafe {
+            Promise::new_with_js_promise(self.reflector().get_jsobject(), cx)
+        }
+    }
+
     #[allow(unsafe_code, unrooted_must_root)]
     unsafe fn new_with_js_promise(obj: HandleObject, cx: *mut JSContext) -> Rc<Promise> {
         assert!(IsPromiseObject(obj));

components/script/dom/testbinding.rs

@@ -25,6 +25,7 @@ use dom::bindings::global::{GlobalRef, global_root_from_context};
 use dom::bindings::js::Root;
 use dom::bindings::mozmap::MozMap;
 use dom::bindings::num::Finite;
+use dom::bindings::refcounted::TrustedPromise;
 use dom::bindings::reflector::{Reflectable, Reflector, reflect_dom_object};
 use dom::bindings::str::{ByteString, DOMString, USVString};
 use dom::bindings::weakref::MutableWeakRef;
@@ -32,12 +33,14 @@ use dom::blob::{Blob, BlobImpl};
 use dom::promise::Promise;
 use dom::promisenativehandler::{PromiseNativeHandler, Callback};
 use dom::url::URL;
-use js::jsapi::{HandleObject, HandleValue, JSContext, JSObject};
+use js::jsapi::{HandleObject, HandleValue, JSContext, JSObject, JSAutoCompartment};
 use js::jsapi::{JS_NewPlainObject, JS_NewUint8ClampedArray};
 use js::jsval::{JSVal, NullValue};
+use script_traits::MsDuration;
 use std::borrow::ToOwned;
 use std::ptr;
 use std::rc::Rc;
+use timers::OneshotTimerCallback;
 use util::prefs::PREFS;
 
 #[dom_struct]
@@ -672,6 +675,17 @@ impl TestBindingMethods for TestBinding {
         p.maybe_reject_error(self.global().r().get_cx(), Error::Type(s.0));
     }
 
+    #[allow(unrooted_must_root)]
+    fn ResolvePromiseDelayed(&self, p: &Promise, value: DOMString, delay: u64) {
+        let promise = p.duplicate();
+        let cb = TestBindingCallback {
+            promise: TrustedPromise::new(promise),
+            value: value,
+        };
+        let _ = self.global().r().schedule_callback(OneshotTimerCallback::TestBindingCallback(cb),
+                                                    MsDuration::new(delay));
+    }
+
     #[allow(unrooted_must_root)]
     fn PromiseNativeHandler(&self,
                             resolve: Option<Rc<SimpleCallback>>,
@@ -760,3 +774,20 @@ impl TestBinding {
     pub unsafe fn condition_satisfied(_: *mut JSContext, _: HandleObject) -> bool { true }
     pub unsafe fn condition_unsatisfied(_: *mut JSContext, _: HandleObject) -> bool { false }
 }
+
+#[derive(JSTraceable, HeapSizeOf)]
+pub struct TestBindingCallback {
+    #[ignore_heap_size_of = "unclear ownership semantics"]
+    promise: TrustedPromise,
+    value: DOMString,
+}
+
+impl TestBindingCallback {
+    #[allow(unrooted_must_root)]
+    pub fn invoke(self) {
+        let p = self.promise.root();
+        let cx = p.global().r().get_cx();
+        let _ac = JSAutoCompartment::new(cx, p.reflector().get_jsobject().get());
+        p.maybe_resolve_native(cx, &self.value);
+    }
+}

components/script/dom/webidls/TestBinding.webidl

@@ -519,6 +519,7 @@ interface TestBinding {
   void promiseResolveNative(Promise<any> p, any value);
   void promiseRejectNative(Promise<any> p, any value);
   void promiseRejectWithTypeError(Promise<any> p, USVString message);
+  void resolvePromiseDelayed(Promise<any> p, DOMString value, unsigned long long ms);
 
   void panic();
 };

components/script/timers.rs

@@ -8,6 +8,7 @@ use dom::bindings::codegen::Bindings::FunctionBinding::Function;
 use dom::bindings::global::GlobalRef;
 use dom::bindings::reflector::Reflectable;
 use dom::bindings::str::DOMString;
+use dom::testbinding::TestBindingCallback;
 use dom::window::ScriptHelpers;
 use dom::xmlhttprequest::XHRTimeoutCallback;
 use euclid::length::Length;
@@ -68,6 +69,7 @@ struct OneshotTimer {
 pub enum OneshotTimerCallback {
     XhrTimeout(XHRTimeoutCallback),
     JsTimer(JsTimerTask),
+    TestBindingCallback(TestBindingCallback),
 }
 
 impl OneshotTimerCallback {
@@ -75,6 +77,7 @@ impl OneshotTimerCallback {
         match self {
             OneshotTimerCallback::XhrTimeout(callback) => callback.invoke(),
             OneshotTimerCallback::JsTimer(task) => task.invoke(this, js_timers),
+            OneshotTimerCallback::TestBindingCallback(callback) => callback.invoke(),
         }
     }
 }

tests/wpt/mozilla/tests/mozilla/promise.html

@@ -51,4 +51,17 @@
           assert_equals(rejected, 'success')
       });
   }, 'Native reject callback gets argument');
+
+  promise_test(function(test) {
+      var t = new TestBinding;
+      var resolved;
+      var p = new Promise(function() {});
+      var start = Date.now();
+      t.resolvePromiseDelayed(p, 'success', 100);
+      return p.then(function(v) {
+          var end = Date.now();
+          assert_true(end - start > 100);
+          assert_equals(v, 'success');
+      });
+  }, 'Native promise from async callback can be resolved');
 </script>