avoid double define for native descriptors

packages/@ember/-internals/metal/lib/alias.ts

@@ -31,6 +31,7 @@ export class AliasedProperty extends Descriptor implements DescriptorWithDepende
 
   setup(obj: object, keyName: string): void {
     assert(`Setting alias '${keyName}' on self`, this.altKey !== keyName);
+    super.setup(obj, keyName);
     let meta = metaFor(obj);
     if (meta.peekWatching(keyName) > 0) {
       addDependentKeys(this, obj, keyName, meta);

packages/@ember/-internals/metal/lib/descriptor.ts

@@ -1,25 +1,25 @@
-import { Descriptor as EmberDescriptor } from './properties';
+import { Descriptor } from './properties';
 
 export default function descriptor(desc: PropertyDescriptor) {
-  return new Descriptor(desc);
+  return new NativeDescriptor(desc);
 }
 
 /**
   A wrapper for a native ES5 descriptor. In an ideal world, we wouldn't need
   this at all, however, the way we currently flatten/merge our mixins require
   a special value to denote a descriptor.
 
-  @class Descriptor
+  @class NativeDescriptor
   @private
 */
-class Descriptor extends EmberDescriptor {
+class NativeDescriptor extends Descriptor {
   desc: PropertyDescriptor;
-  enumerable: boolean;
 
   constructor(desc: PropertyDescriptor) {
     super();
     this.desc = desc;
     this.enumerable = desc.enumerable !== false;
+    this.configurable = desc.configurable !== false;
   }
 
   setup(obj: object, key: string) {

packages/@ember/-internals/metal/lib/properties.ts

@@ -27,14 +27,18 @@ export type InheritingGetterFunction = ((this: object) => void) & {
   @private
 */
 export abstract class Descriptor {
-  isDescriptor: boolean;
-  enumerable: boolean;
-  constructor() {
-    this.isDescriptor = true;
-    this.enumerable = true;
+  isDescriptor = true;
+  enumerable = true;
+  configurable = true;
+
+  setup(obj: object, keyName: string): void {
+    Object.defineProperty(obj, keyName, {
+      enumerable: this.enumerable,
+      configurable: this.configurable,
+      get: DESCRIPTOR_GETTER_FUNCTION(keyName, this),
+    });
   }
 
-  setup(_obj: object, _keyName: string): void {}
   teardown(_obj: object, _keyName: string, _meta: Meta): void {}
 
   abstract get(obj: object, keyName: string): any | null | undefined;
@@ -188,16 +192,8 @@ export function defineProperty(
   let value;
   if (desc instanceof Descriptor) {
     value = desc;
-
-    Object.defineProperty(obj, keyName, {
-      configurable: true,
-      enumerable,
-      get: DESCRIPTOR_GETTER_FUNCTION(keyName, value),
-    });
-
-    meta.writeDescriptors(keyName, value);
-
     desc.setup(obj, keyName);
+    meta.writeDescriptors(keyName, value);
   } else if (desc === undefined || desc === null) {
     value = data;
 

packages/@ember/-internals/metal/lib/property_get.ts

@@ -131,14 +131,6 @@ export function get(obj: object, keyName: string): any {
         }
       );
 
-      Object.defineProperty(obj, keyName, {
-        configurable: true,
-        enumerable: value.enumerable === false,
-        get() {
-          return value.get(this, keyName);
-        },
-      });
-
       meta(obj).writeDescriptors(keyName, value);
 
       value.setup(obj, keyName);

packages/@ember/-internals/metal/lib/property_set.ts

@@ -108,14 +108,6 @@ export function set(obj: object, keyName: string, value: any, tolerant?: boolean
 
     let cv: Descriptor = currentValue;
 
-    Object.defineProperty(obj, keyName, {
-      configurable: true,
-      enumerable: cv.enumerable === false,
-      get() {
-        return cv.get(this, keyName);
-      },
-    });
-
     meta(obj).writeDescriptors(keyName, cv);
 
     cv.setup(obj, keyName);

packages/@ember/-internals/metal/tests/descriptor_test.js

@@ -1,6 +1,7 @@
 import { Object as EmberObject } from '@ember/-internals/runtime';
 import { Mixin, defineProperty, descriptor } from '..';
 import { moduleFor, AbstractTestCase } from 'internal-test-helpers';
+import { isEdge } from 'internal-test-helpers';
 
 let classes = [
   class {
@@ -148,7 +149,7 @@ let classes = [
   },
 ];
 
-classes.forEach(TestClass => {
+classes.forEach((TestClass, testCaseIndex) => {
   moduleFor(
     TestClass.module('@ember/-internals/metal/descriptor'),
     class extends AbstractTestCase {
@@ -182,7 +183,12 @@ classes.forEach(TestClass => {
 
         let source = factory.source();
 
-        assert.throws(() => delete source.foo, TypeError);
+        if (isEdge && testCaseIndex === 0) {
+          // https://github.com/emberjs/ember.js/pull/16741#issuecomment-420963181
+          assert.equal(delete source.foo, false);
+        } else {
+          assert.throws(() => delete source.foo, TypeError);
+        }
 
         assert.throws(
           () =>

packages/internal-test-helpers/index.js

@@ -27,5 +27,5 @@ export {
   ModuleBasedResolver as ModuleBasedTestResolver,
 } from './lib/test-resolver';
 
-export { isIE11 } from './lib/browser-detect';
+export { isIE11, isEdge } from './lib/browser-detect';
 export { verifyInjection, verifyRegistration } from './lib/registry-check';

packages/internal-test-helpers/lib/browser-detect.ts

@@ -8,3 +8,4 @@ declare global {
   }
 }
 export const isIE11 = !window.ActiveXObject && 'ActiveXObject' in window;
+export const isEdge = /Edge/.test(navigator.userAgent);