[BUGFIX lts] Ensures that tracked properties initialize property

packages/@ember/-internals/glimmer/tests/integration/components/tracked-test.js

@@ -14,6 +14,44 @@ import { Component } from '../../utils/helpers';
 moduleFor(
   'Component Tracked Properties',
   class extends RenderingTestCase {
+    '@test simple test using classic component'() {
+      let personId = 0;
+      class Person {
+        @tracked first;
+        @tracked last;
+
+        constructor(first, last) {
+          this.id = personId++;
+          this.first = first;
+          this.last = last;
+        }
+      }
+
+      class PersonComponent extends Component {
+        @tracked first;
+        @tracked last;
+
+        get person() {
+          return new Person(this.first, this.last);
+        }
+      }
+
+      this.registerComponent('person-wrapper', {
+        ComponentClass: PersonComponent,
+        template: '{{@first}} {{@last}} | {{this.person.first}} {{this.person.last}}',
+      });
+
+      this.render('<PersonWrapper @first={{first}} @last={{last}} />', {
+        first: 'robert',
+        last: 'jackson',
+      });
+
+      this.assertText('robert jackson | robert jackson');
+
+      runTask(() => this.context.set('first', 'max'));
+      this.assertText('max jackson | max jackson');
+    }
+
     '@test simple test using glimmerish component'() {
       let personId = 0;
       class Person {

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

@@ -1,6 +1,5 @@
 import { Meta, meta as metaFor, peekMeta } from '@ember/-internals/meta';
 import { assert } from '@ember/debug';
-import { _WeakSet as WeakSet } from '@glimmer/util';
 
 export type DecoratorPropertyDescriptor = (PropertyDescriptor & { initializer?: any }) | undefined;
 
@@ -80,17 +79,11 @@ function DESCRIPTOR_SETTER_FUNCTION(
   name: string,
   descriptor: ComputedDescriptor
 ): (value: any) => void {
-  let func = function CPSETTER_FUNCTION(this: object, value: any): void {
+  return function CPSETTER_FUNCTION(this: object, value: any): void {
     return descriptor.set(this, name, value);
   };
-
-  CP_SETTER_FUNCS.add(func);
-
-  return func;
 }
 
-export const CP_SETTER_FUNCS = new WeakSet();
-
 export function makeComputedDecorator(
   desc: ComputedDescriptor,
   DecoratorClass: { prototype: object }

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

@@ -1,13 +1,8 @@
-import {
-  HAS_NATIVE_PROXY,
-  lookupDescriptor,
-  setWithMandatorySetter,
-  toString,
-} from '@ember/-internals/utils';
+import { HAS_NATIVE_PROXY, setWithMandatorySetter, toString } from '@ember/-internals/utils';
 import { assert } from '@ember/debug';
 import EmberError from '@ember/error';
 import { DEBUG } from '@glimmer/env';
-import { CP_SETTER_FUNCS } from './decorator';
+import { descriptorForProperty } from './decorator';
 import { isPath } from './path_cache';
 import { notifyPropertyChange } from './property_events';
 import { _getPath as getPath, getPossibleMandatoryProxyValue } from './property_get';
@@ -72,11 +67,10 @@ export function set(obj: object, keyName: string, value: any, tolerant?: boolean
     return setPath(obj, keyName, value, tolerant);
   }
 
-  let descriptor = lookupDescriptor(obj, keyName);
-  let setter = descriptor === null ? undefined : descriptor.set;
+  let descriptor = descriptorForProperty(obj, keyName);
 
-  if (setter !== undefined && CP_SETTER_FUNCS.has(setter)) {
-    obj[keyName] = value;
+  if (descriptor !== undefined) {
+    descriptor.set(obj, keyName, value);
     return value;
   }
 

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

@@ -5,7 +5,6 @@ import { DEBUG } from '@glimmer/env';
 import { consumeTag, dirtyTagFor, tagFor, trackedData } from '@glimmer/validator';
 import { CHAIN_PASS_THROUGH } from './chain-tags';
 import {
-  CP_SETTER_FUNCS,
   Decorator,
   DecoratorPropertyDescriptor,
   isElementDescriptor,
@@ -183,10 +182,21 @@ function descriptorForField([target, key, desc]: [
     set,
   };
 
-  metaFor(target).writeDescriptors(key, newDesc);
-
-  CP_SETTER_FUNCS.add(set);
-  CHAIN_PASS_THROUGH.add(newDesc);
+  metaFor(target).writeDescriptors(key, new TrackedDescriptor(get, set));
 
   return newDesc;
 }
+
+class TrackedDescriptor {
+  constructor(private _get: () => unknown, private _set: (value: unknown) => void) {
+    CHAIN_PASS_THROUGH.add(this);
+  }
+
+  get(obj: object) {
+    return this._get.call(obj);
+  }
+
+  set(obj: object, _key: string, value: unknown) {
+    this._set.call(obj, value);
+  }
+}