port @codeworrior's stefanpenner/es6-promise#339

lib/rsvp/promise.js

@@ -228,8 +228,12 @@ class Promise {
     let promise = this;
     let constructor = promise.constructor;
 
-    return promise.then(value => constructor.resolve(callback()).then(() => value),
-                       reason => constructor.resolve(callback()).then(() => { throw reason; }), label);
+    if (typeof callback === 'function') {
+      return promise.then(value => constructor.resolve(callback()).then(() => value),
+                         reason => constructor.resolve(callback()).then(() => { throw reason; }));
+    }
+
+    return promise.then(callback, callback);
   }
 }
 

test/extension-test.js

@@ -2508,6 +2508,23 @@ describe("RSVP extensions", function() {
           });
         });
       });
+
+      it("preserves the original fulfillment value even if a non-callable callback is given", function(done) {
+        var fulfillmentValue = 1;
+        var promise = Promise.resolve(fulfillmentValue);
+         promise['finally']().then(function(value) {
+          assert.equal(fulfillmentValue, value);
+          done();
+        });
+      });
+       it("preserves the original rejection reason even if a non-callable callback is given", function(done) {
+        var rejectionReason = new Error();
+        var promise = Promise.reject(rejectionReason);
+         promise['finally']().then(undefined, function(reason) {
+          assert.equal(rejectionReason, reason);
+          done();
+        });
+      });
     });
 
     describe("inheritance", function() {