feat(ivy): support for the ngForOf directive, with tests (#21430)

Implement NgOnChangesFeature, ViewContainerRef, TemplateRef,
and the renderEmbeddedTemplate instruction, and wire together the
pieces required for the ngForOf directive to work.

PR Close #21430

packages/core/src/render3/definition.ts

@@ -6,13 +6,15 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import {SimpleChange} from '../change_detection/change_detection_util';
+import {OnChanges, SimpleChanges} from '../metadata/lifecycle_hooks';
 import {RendererType2} from '../render/api';
 import {Type} from '../type';
 import {resolveRendererType2} from '../view/util';
 
 import {diPublic} from './di';
 import {componentRefresh} from './instructions';
-import {ComponentDef, ComponentDefArgs, DirectiveDef, DirectiveDefArgs} from './interfaces/definition';
+import {ComponentDef, ComponentDefArgs, DirectiveDef, DirectiveDefArgs, TypedDirectiveDef} from './interfaces/definition';
 
 
 
@@ -54,8 +56,57 @@ export function defineComponent<T>(componentDefinition: ComponentDefArgs<T>): Co
   return def;
 }
 
-export function NgOnChangesFeature<T>(definition: DirectiveDef<T>) {
-  // TODO: implement. See: https://app.asana.com/0/443577627818617/465170715764659
+
+const PRIVATE_PREFIX = '__ngOnChanges_';
+
+type OnChangesExpando = OnChanges & {
+  __ngOnChanges_: SimpleChanges|null|undefined;
+  [key: string]: any;
+};
+
+export function NgOnChangesFeature<T>(type: Type<T>): (definition: DirectiveDef<any>) => void {
+  return function(definition: DirectiveDef<any>): void {
+    const inputs = definition.inputs;
+    const proto = type.prototype;
+    // Place where we will store SimpleChanges if there is a change
+    Object.defineProperty(proto, PRIVATE_PREFIX, {value: undefined, writable: true});
+    for (let pubKey in inputs) {
+      const minKey = inputs[pubKey];
+      const privateMinKey = PRIVATE_PREFIX + minKey;
+      // Create a place where the actual value will be stored and make it non-enumerable
+      Object.defineProperty(proto, privateMinKey, {value: undefined, writable: true});
+
+      const existingDesc = Object.getOwnPropertyDescriptor(proto, minKey);
+
+      // create a getter and setter for property
+      Object.defineProperty(proto, minKey, {
+        get: function(this: OnChangesExpando) {
+          return (existingDesc && existingDesc.get) ? existingDesc.get.call(this) :
+                                                      this[privateMinKey];
+        },
+        set: function(this: OnChangesExpando, value: any) {
+          let simpleChanges = this[PRIVATE_PREFIX];
+          let isFirstChange = simpleChanges === undefined;
+          if (simpleChanges == null) {
+            simpleChanges = this[PRIVATE_PREFIX] = {};
+          }
+          simpleChanges[pubKey] = new SimpleChange(this[privateMinKey], value, isFirstChange);
+          (existingDesc && existingDesc.set) ? existingDesc.set.call(this, value) :
+                                               this[privateMinKey] = value;
+        }
+      });
+    }
+    proto.ngDoCheck = (function(delegateDoCheck) {
+      return function(this: OnChangesExpando) {
+        let simpleChanges = this[PRIVATE_PREFIX];
+        if (simpleChanges != null) {
+          this.ngOnChanges(simpleChanges);
+          this[PRIVATE_PREFIX] = null;
+        }
+        delegateDoCheck && delegateDoCheck.apply(this);
+      };
+    })(proto.ngDoCheck);
+  };
 }
 
 export function PublicFeature<T>(definition: DirectiveDef<T>) {