feat(ivy): add a runtime feature to copy cmp/dir definitions (#33362)

This commit adds CopyDefinitionFeature, which supports the case where an
entire decorator (@Component or @Directive) is inherited from parent to
child.

The existing inheritance feature, InheritDefinitionFeature, supports merging
of parent and child definitions when both were originally present. This
merges things like inputs, outputs, host bindings, etc.

CopyDefinitionFeature, on the other hand, compensates for a definition that
was missing entirely on the child class, by copying fields that aren't
ordinarily inherited (like the template function itself).

This feature is intended to only be used as part of ngcc code generation.

PR Close #33362

packages/compiler/src/render3/r3_identifiers.ts

@@ -284,6 +284,9 @@ export class Identifiers {
   static InheritDefinitionFeature:
       o.ExternalReference = {name: 'ɵɵInheritDefinitionFeature', moduleName: CORE};
 
+  static CopyDefinitionFeature:
+      o.ExternalReference = {name: 'ɵɵCopyDefinitionFeature', moduleName: CORE};
+
   static ProvidersFeature: o.ExternalReference = {name: 'ɵɵProvidersFeature', moduleName: CORE};
 
   static listener: o.ExternalReference = {name: 'ɵɵlistener', moduleName: CORE};

packages/core/src/core_render3_private_export.ts

@@ -40,6 +40,7 @@ export {
   ɵɵsetNgModuleScope,
   ɵɵtemplateRefExtractor,
   ɵɵProvidersFeature,
+  ɵɵCopyDefinitionFeature,
   ɵɵInheritDefinitionFeature,
   ɵɵNgOnChangesFeature,
   LifecycleHooksFeature as ɵLifecycleHooksFeature,

packages/core/src/render3/features/copy_definition_feature.ts

@@ -0,0 +1,93 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {ComponentDef, DirectiveDef} from '../interfaces/definition';
+import {isComponentDef} from '../interfaces/type_checks';
+
+import {getSuperType} from './inherit_definition_feature';
+
+/**
+ * Fields which exist on either directive or component definitions, and need to be copied from
+ * parent to child classes by the `ɵɵCopyDefinitionFeature`.
+ */
+const COPY_DIRECTIVE_FIELDS: (keyof DirectiveDef<unknown>)[] = [
+  // The child class should use the providers of its parent.
+  'providersResolver',
+
+  // Not listed here are any fields which are handled by the `ɵɵInheritDefinitionFeature`, such
+  // as inputs, outputs, and host binding functions.
+];
+
+/**
+ * Fields which exist only on component definitions, and need to be copied from parent to child
+ * classes by the `ɵɵCopyDefinitionFeature`.
+ *
+ * The type here allows any field of `ComponentDef` which is not also a property of `DirectiveDef`,
+ * since those should go in `COPY_DIRECTIVE_FIELDS` above.
+ */
+const COPY_COMPONENT_FIELDS: Exclude<keyof ComponentDef<unknown>, keyof DirectiveDef<unknown>>[] = [
+  // The child class should use the template function of its parent, including all template
+  // semantics.
+  'template',
+  'decls',
+  'consts',
+  'vars',
+  'onPush',
+  'ngContentSelectors',
+
+  // The child class should use the CSS styles of its parent, including all styling semantics.
+  'styles',
+  'encapsulation',
+
+  // The child class should be checked by the runtime in the same way as its parent.
+  'schemas',
+];
+
+/**
+ * Copies the fields not handled by the `ɵɵInheritDefinitionFeature` from the supertype of a
+ * definition.
+ *
+ * This exists primarily to support ngcc migration of an existing View Engine pattern, where an
+ * entire decorator is inherited from a parent to a child class. When ngcc detects this case, it
+ * generates a skeleton definition on the child class, and applies this feature.
+ *
+ * The `ɵɵCopyDefinitionFeature` then copies any needed fields from the parent class' definition,
+ * including things like the component template function.
+ *
+ * @param definition The definition of a child class which inherits from a parent class with its
+ * own definition.
+ *
+ * @codeGenApi
+ */
+export function ɵɵCopyDefinitionFeature(definition: DirectiveDef<any>| ComponentDef<any>): void {
+  let superType = getSuperType(definition.type) !;
+
+  let superDef: DirectiveDef<any>|ComponentDef<any>|undefined = undefined;
+  if (isComponentDef(definition)) {
+    // Don't use getComponentDef/getDirectiveDef. This logic relies on inheritance.
+    superDef = superType.ɵcmp !;
+  } else {
+    // Don't use getComponentDef/getDirectiveDef. This logic relies on inheritance.
+    superDef = superType.ɵdir !;
+  }
+
+  // Needed because `definition` fields are readonly.
+  const defAny = (definition as any);
+
+  // Copy over any fields that apply to either directives or components.
+  for (const field of COPY_DIRECTIVE_FIELDS) {
+    defAny[field] = superDef[field];
+  }
+
+  if (isComponentDef(superDef)) {
+    // Copy over any component-specific fields.
+    for (const field of COPY_COMPONENT_FIELDS) {
+      defAny[field] = superDef[field];
+    }
+  }
+}

packages/core/src/render3/features/inherit_definition_feature.ts

@@ -14,7 +14,7 @@ import {isComponentDef} from '../interfaces/type_checks';
 
 import {ɵɵNgOnChangesFeature} from './ng_onchanges_feature';
 
-function getSuperType(type: Type<any>): Type<any>&
+export function getSuperType(type: Type<any>): Type<any>&
     {ɵcmp?: ComponentDef<any>, ɵdir?: DirectiveDef<any>} {
   return Object.getPrototypeOf(type.prototype).constructor;
 }

packages/core/src/render3/index.ts

@@ -7,6 +7,7 @@
  */
 import {LifecycleHooksFeature, renderComponent, whenRendered} from './component';
 import {ɵɵdefineBase, ɵɵdefineComponent, ɵɵdefineDirective, ɵɵdefineNgModule, ɵɵdefinePipe, ɵɵsetComponentScope, ɵɵsetNgModuleScope} from './definition';
+import {ɵɵCopyDefinitionFeature} from './features/copy_definition_feature';
 import {ɵɵInheritDefinitionFeature} from './features/inherit_definition_feature';
 import {ɵɵNgOnChangesFeature} from './features/ng_onchanges_feature';
 import {ɵɵProvidersFeature} from './features/providers_feature';
@@ -210,6 +211,7 @@ export {
   ɵɵDirectiveDefWithMeta,
   DirectiveType,
   ɵɵNgOnChangesFeature,
+  ɵɵCopyDefinitionFeature,
   ɵɵInheritDefinitionFeature,
   ɵɵProvidersFeature,
   PipeDef,

packages/core/src/render3/jit/environment.ts

@@ -46,6 +46,7 @@ export const angularCoreEnv: {[name: string]: Function} =
        'ɵɵtemplateRefExtractor': r3.ɵɵtemplateRefExtractor,
        'ɵɵNgOnChangesFeature': r3.ɵɵNgOnChangesFeature,
        'ɵɵProvidersFeature': r3.ɵɵProvidersFeature,
+       'ɵɵCopyDefinitionFeature': r3.ɵɵCopyDefinitionFeature,
        'ɵɵInheritDefinitionFeature': r3.ɵɵInheritDefinitionFeature,
        'ɵɵcontainer': r3.ɵɵcontainer,
        'ɵɵnextContext': r3.ɵɵnextContext,

packages/core/test/acceptance/copy_definition_feature_spec.ts

@@ -0,0 +1,86 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {Component, NgModule, ɵɵCopyDefinitionFeature as CopyDefinitionFeature, ɵɵInheritDefinitionFeature as InheritDefinitionFeature, ɵɵdefineComponent as defineComponent} from '@angular/core';
+import {TestBed} from '@angular/core/testing';
+import {onlyInIvy} from '@angular/private/testing';
+
+describe('Ivy CopyDefinitionFeature', () => {
+  onlyInIvy('this feature is not required in View Engine')
+      .it('should copy the template function of a component definition from parent to child',
+          () => {
+
+            // It would be nice if the base component could be JIT compiled. However, this creates
+            // a getter for ɵcmp which precludes adding a static definition of that field for the
+            // child class.
+            // TODO(alxhub): see if there's a cleaner way to do this.
+            class BaseComponent {
+              name !: string;
+              static ɵcmp = defineComponent({
+                type: BaseComponent,
+                selectors: [['some-cmp']],
+                decls: 0,
+                vars: 0,
+                inputs: {name: 'name'},
+                template: function BaseComponent_Template(rf, ctx) { ctx.rendered = true; },
+                encapsulation: 2
+              });
+              static ɵfac = function BaseComponent_Factory(t: any) {
+                return new (t || BaseComponent)();
+              };
+
+              rendered = false;
+            }
+
+            class ChildComponent extends BaseComponent {
+              static ɵcmp = defineComponent({
+                type: ChildComponent,
+                selectors: [['some-cmp']],
+                features: [InheritDefinitionFeature, CopyDefinitionFeature],
+                decls: 0,
+                vars: 0,
+                template: function ChildComponent_Template(rf, ctx) {},
+                encapsulation: 2
+              });
+              static ɵfac = function ChildComponent_Factory(t: any) {
+                return new (t || ChildComponent)();
+              };
+            }
+
+            @NgModule({
+              declarations: [ChildComponent],
+              exports: [ChildComponent],
+            })
+            class Module {
+            }
+
+            @Component({
+              selector: 'test-cmp',
+              template: '<some-cmp name="Success!"></some-cmp>',
+            })
+            class TestCmp {
+            }
+
+            TestBed.configureTestingModule({
+              declarations: [TestCmp],
+              imports: [Module],
+            });
+
+            const fixture = TestBed.createComponent(TestCmp);
+
+            // The child component should have matched and been instantiated.
+            const child = fixture.debugElement.children[0].componentInstance as ChildComponent;
+            expect(child instanceof ChildComponent).toBe(true);
+
+            // And the base class template function should've been called.
+            expect(child.rendered).toBe(true);
+
+            // The input binding should have worked.
+            expect(child.name).toBe('Success!');
+          });
+});

tools/public_api_guard/core/core.d.ts

@@ -756,6 +756,8 @@ export declare function ɵɵcontainerRefreshStart(index: number): void;
 
 export declare function ɵɵcontentQuery<T>(directiveIndex: number, predicate: Type<any> | string[], descend: boolean, read?: any): void;
 
+export declare function ɵɵCopyDefinitionFeature(definition: DirectiveDef<any> | ComponentDef<any>): void;
+
 export declare const ɵɵdefaultStyleSanitizer: StyleSanitizeFn;
 
 export declare function ɵɵdefineBase<T>(baseDefinition: {