onerror is now provided (via 2nd arg) the promises label

README.md

@@ -175,6 +175,20 @@ RSVP.on('error', function(reason) {
 });
 ```
 
+`RSVP` allows Promises to be labeled: `Promise.resovle(value, 'I AM A LABEL')`
+If provided, this label is passed as the second argument to `RSVP.on('error')`
+
+```javascript
+RSVP.on('error', function(reason, label) {
+  if (label) {
+    console.error(label);
+  }
+
+  console.assert(false, reason);
+});
+```
+
+
 **NOTE:** promises do allow for errors to be handled asynchronously, so
 this callback may result in false positives.
 
@@ -262,7 +276,7 @@ one of the following formats:
 ## Deferred
 
 > The `RSVP.Promise` constructor is generally a better, less error-prone choice
-> than `RSVP.defer()`. Promises are recommended unless the specific 
+> than `RSVP.defer()`. Promises are recommended unless the specific
 > properties of deferred are needed.
 
 Sometimes one needs to create a deferred object, without immediately specifying
@@ -345,7 +359,7 @@ RSVP.on('chained', listener);
 RSVP.on('fulfilled', listener);
 RSVP.on('rejected', listener);
 ```
-        
+
 Events are only triggered when `RSVP.configure('instrument')` is true, although
 listeners can be registered at any time.
 

lib/rsvp/events.js

@@ -190,15 +190,15 @@ export default {
     @param {*} options optional value to be passed to any event handlers for
     the given `eventName`
   */
-  'trigger': function(eventName, options) {
+  'trigger': function(eventName, options, label) {
     var allCallbacks = callbacksFor(this), callbacks, callback;
 
     if (callbacks = allCallbacks[eventName]) {
       // Don't cache the callbacks.length since it may grow
       for (var i=0; i<callbacks.length; i++) {
         callback = callbacks[i];
 
-        callback(options);
+        callback(options, label);
       }
     }
   }

lib/rsvp/promise.js

@@ -176,7 +176,7 @@ Promise.prototype = {
     var promise = this;
     config.after(function() {
       if (promise._onError) {
-        config['trigger']('error', reason);
+        config['trigger']('error', reason, promise._label);
       }
     });
   },

test/extension-test.js

@@ -1440,6 +1440,23 @@ describe("RSVP extensions", function() {
       });
     });
 
+    it("onerror gets label if provided", function(done) {
+      var thrownError = new Error();
+
+      RSVP.configure('onerror', function(error, label) {
+        assert.equal(error, thrownError, "The thrown error is passed in");
+        assert.equal(label, 'i am label', "the label for the given promise is also provided");
+        done();
+      });
+
+      new RSVP.Promise(function(resolve, reject) {
+        reject(thrownError);
+      }, 'i am label').then(function() {
+        // doesn't get here
+        assert(false);
+      });
+    });
+
     it("When provided, handled exceptions are not sent to it", function(done) {
       var thrownError = new Error();