[BUGFIX beta] CPs check presence of getter function

packages/ember-metal/lib/computed.js

@@ -115,9 +115,20 @@ function ComputedProperty(config, opts) {
   if (typeof config === 'function') {
     this._getter = config;
   } else {
+    Ember.assert('Ember.computed expects a function or an object as last argument.', typeof config === 'object' && !Array.isArray(config));
+    Ember.assert('Config object pased to a Ember.computed can only contain `get` or `set` keys.', (function() {
+      let keys = Object.keys(config);
+      for (let i = 0; i < keys.length; i++) {
+        if (keys[i] !== 'get' && keys[i] !== 'set') {
+          return false;
+        }
+      }
+      return true;
+    })());
     this._getter = config.get;
     this._setter = config.set;
   }
+  Ember.assert('Computed properties must receive a getter or a setter, you passed none.', !!this._getter || !!this._setter);
   this._dependentKeys = undefined;
   this._suspended = undefined;
   this._meta = undefined;

packages/ember-metal/tests/computed_test.js

@@ -26,6 +26,29 @@ QUnit.test('computed property should be an instance of descriptor', function() {
   ok(computed(function() {}) instanceof Descriptor);
 });
 
+QUnit.test('computed properties assert the presence of a getter or setter function', function() {
+  expectAssertion(function() {
+    computed('nogetternorsetter', {});
+  }, 'Computed properties must receive a getter or a setter, you passed none.');
+});
+
+QUnit.test('computed properties check for the presence of a function or configuration object', function() {
+  expectAssertion(function() {
+    computed('nolastargument');
+  }, 'Ember.computed expects a function or an object as last argument.');
+});
+
+QUnit.test('computed properties defined with an object only allow `get` and `set` keys', function() {
+  expectAssertion(function() {
+    computed({
+      get() {},
+      set() {},
+      other() {}
+    });
+  }, 'Config object pased to a Ember.computed can only contain `get` or `set` keys.');
+});
+
+
 QUnit.test('defining computed property should invoke property on get', function() {
   var obj = {};
   var count = 0;