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fix(core): default the Component decorator to OnPush change detection in JIT #70261

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fix(core): default the Component decorator to OnPush change detection in JIT #70261

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2 changes: 1 addition & 1 deletion packages/core/src/metadata/directives.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -679,7 +679,7 @@ export interface Component extends Directive {
*/
export const Component: ComponentDecorator = makeDecorator(
'Component',
(c: Component = {}) => ({changeDetection: ChangeDetectionStrategy.Eager, ...c}),
(c: Component = {}) => ({changeDetection: ChangeDetectionStrategy.OnPush, ...c}),
Directive,
undefined,
(type: Type<any>, meta: Component) => compileComponent(type, meta),
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16 changes: 16 additions & 0 deletions packages/core/test/acceptance/change_detection_spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,7 @@ import {
ViewChildren,
ViewContainerRef,
} from '../../src/core';
import {getComponentDef} from '../../src/render3/def_getters';
import {ComponentFixture, ComponentFixtureAutoDetect, TestBed} from '../../testing';

describe('change detection', () => {
Expand All @@ -56,6 +57,21 @@ describe('change detection', () => {
TestBed.inject(ApplicationRef);
}).not.toThrow();
});
it('defaults an unspecified changeDetection strategy to OnPush, matching the AOT compiler default', () => {
// The `@Component` decorator itself must default to OnPush, the same way the AOT
// compiler does (see `compileComponentFromMetadata` in
// packages/compiler/src/render3/view/compiler.ts). Before this fix, the JIT decorator
// in this file still defaulted to `ChangeDetectionStrategy.Eager`, so a component
// without an explicit `changeDetection` behaved differently under TestBed/JIT than in
// a production AOT build.
@Component({
selector: 'default-cd-comp',
template: '',
})
class DefaultCdComponent {}

expect(getComponentDef(DefaultCdComponent)!.onPush).toBe(true);
});
describe('embedded views', () => {
@Directive({
selector: '[viewManipulation]',
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