Failing test and fix for #17243

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

@@ -13,7 +13,7 @@ import {
 
 import { run } from '@ember/runloop';
 import { DEBUG } from '@glimmer/env';
-import { set, get, observer, on, computed } from '@ember/-internals/metal';
+import { alias, set, get, observer, on, computed } from '@ember/-internals/metal';
 import Service, { inject as injectService } from '@ember/service';
 import { Object as EmberObject, A as emberA } from '@ember/-internals/runtime';
 import { jQueryDisabled } from '@ember/-internals/views';
@@ -3576,6 +3576,67 @@ moduleFor(
 
       this.render('{{foo-bar}}');
     }
+
+    ['@test ensure aliases are watched properly [GH#17243]']() {
+      let fooInstance, barInstance;
+
+      let FooComponent = Component.extend({
+        source: 'first',
+        foo: alias('source'),
+
+        init() {
+          this._super(...arguments);
+          fooInstance = this;
+        },
+      });
+
+      this.registerComponent('foo', {
+        ComponentClass: FooComponent,
+        template: '{{this.foo}}',
+      });
+
+      let BarComponent = Component.extend({
+        target: null,
+
+        init() {
+          this._super(...arguments);
+          barInstance = this;
+        },
+
+        bar: computed('target.foo', function() {
+          if (this.target) {
+            return this.target.foo.toUpperCase();
+          }
+        }),
+      });
+
+      this.registerComponent('bar', {
+        ComponentClass: BarComponent,
+        template: '{{this.bar}}',
+      });
+
+      this.render('[<Foo />][<Bar />]');
+
+      this.assertText('[first][]');
+
+      // addObserver
+      runTask(() => set(barInstance, 'target', fooInstance));
+
+      this.assertText('[first][FIRST]');
+
+      runTask(() => set(fooInstance, 'source', 'second'));
+
+      this.assertText('[second][SECOND]');
+
+      // removeObserver
+      runTask(() => set(barInstance, 'target', null));
+
+      this.assertText('[second][]');
+
+      runTask(() => set(fooInstance, 'source', 'third'));
+
+      this.assertText('[third][]');
+    }
   }
 );
 

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

@@ -46,10 +46,6 @@ export class AliasedProperty extends Descriptor implements DescriptorWithDepende
     this.consume(obj, keyName, meta);
   }
 
-  didUnwatch(obj: object, keyName: string, meta: Meta): void {
-    this.unconsume(obj, keyName, meta);
-  }
-
   get(obj: object, keyName: string): any {
     let ret = get(obj, this.altKey);
     this.consume(obj, keyName, metaFor(obj));

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

@@ -7,6 +7,7 @@ import {
   addObserver,
   removeObserver,
   tagFor,
+  tagForProperty,
 } from '..';
 import { meta } from '@ember/-internals/meta';
 import { moduleFor, AbstractTestCase } from 'internal-test-helpers';
@@ -164,5 +165,57 @@ moduleFor(
 
       assert.equal(count, 2);
     }
+
+    ['@test property tags are bumped when the source changes [GH#17243]'](assert) {
+      function assertPropertyTagChanged(obj, keyName, callback) {
+        let tag = tagForProperty(obj, keyName);
+        let before = tag.value();
+
+        callback();
+
+        let after = tag.value();
+
+        assert.notEqual(after, before, `tagForProperty ${keyName} should change`);
+      }
+
+      function assertPropertyTagUnchanged(obj, keyName, callback) {
+        let tag = tagForProperty(obj, keyName);
+        let before = tag.value();
+
+        callback();
+
+        let after = tag.value();
+
+        assert.equal(after, before, `tagForProperty ${keyName} should not change`);
+      }
+
+      defineProperty(obj, 'bar', alias('foo.faz'));
+
+      assertPropertyTagUnchanged(obj, 'bar', () => {
+        assert.equal(get(obj, 'bar'), 'FOO');
+      });
+
+      assertPropertyTagChanged(obj, 'bar', () => {
+        set(obj, 'foo.faz', 'BAR');
+      });
+
+      assertPropertyTagUnchanged(obj, 'bar', () => {
+        assert.equal(get(obj, 'bar'), 'BAR');
+      });
+
+      assertPropertyTagUnchanged(obj, 'bar', () => {
+        // trigger willWatch, then didUnwatch
+        addObserver(obj, 'bar', incrementCount);
+        removeObserver(obj, 'bar', incrementCount);
+      });
+
+      assertPropertyTagChanged(obj, 'bar', () => {
+        set(obj, 'foo.faz', 'FOO');
+      });
+
+      assertPropertyTagUnchanged(obj, 'bar', () => {
+        assert.equal(get(obj, 'bar'), 'FOO');
+      });
+    }
   }
 );