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cexbrayatjasonaden
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feat(common): stricter types for SlicePipe (#30156)
Adds overloads to the `transform` methods of `SlicePipe`, to have better types than `any` for `value` and `any` as a return. With this commit, using `slice` in an `ngFor` still allow to type-check the content of the `ngFor` with `fullTemplateTypeCheck` enabled in Ivy: <div *ngFor="let user of users | slice:0:2">{{ user.typo }}</div> | `typo` does not exist on type `UserModel` whereas it is currently not catched (as the return of `slice` is `any`) neither in VE nor in Ivy. BREAKING CHANGE `SlicePipe` now only accepts an array of values, a string, null or undefined. This was already the case in practice, and it still throws at runtime if another type is given. But it is now a compilation error to try to call it with an unsupported type. PR Close #30156
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Lines changed: 16 additions & 2 deletions

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‎packages/common/src/pipes/slice_pipe.ts‎

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@@ -62,6 +62,10 @@ export class SlicePipe implements PipeTransform {
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* - **if positive**: return all items before `end` index of the list or string.
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* - **if negative**: return all items before `end` index from the end of the list or string.
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*/
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transform<T>(value: ReadonlyArray<T>, start: number, end?: number): Array<T>;
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transform(value: string, start: number, end?: number): string;
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transform(value: null, start: number, end?: number): null;
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transform(value: undefined, start: number, end?: number): undefined;
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transform(value: any, start: number, end?: number): any {
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if (value == null) return value;
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‎packages/common/test/pipes/slice_pipe_spec.ts‎

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@@ -26,16 +26,23 @@ import {expect} from '@angular/platform-browser/testing/src/matchers';
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describe('supports', () => {
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it('should support strings', () => { expect(() => pipe.transform(str, 0)).not.toThrow(); });
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it('should support lists', () => { expect(() => pipe.transform(list, 0)).not.toThrow(); });
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it('should support readonly lists',
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() => { expect(() => pipe.transform(list as ReadonlyArray<number>, 0)).not.toThrow(); });
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it('should not support other objects',
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() => { expect(() => pipe.transform({}, 0)).toThrow(); });
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// this would not compile
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// so we cast as `any` to check that it throws for unsupported objects
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() => { expect(() => pipe.transform({} as any, 0)).toThrow(); });
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});
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describe('transform', () => {
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it('should return null if the value is null',
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() => { expect(pipe.transform(null, 1)).toBe(null); });
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it('should return undefined if the value is undefined',
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() => { expect(pipe.transform(undefined, 1)).toBe(undefined); });
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it('should return all items after START index when START is positive and END is omitted',
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() => {
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expect(pipe.transform(list, 3)).toEqual([4, 5]);

‎tools/public_api_guard/common/common.d.ts‎

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@@ -410,7 +410,10 @@ export interface PopStateEvent {
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export declare function registerLocaleData(data: any, localeId?: string | any, extraData?: any): void;
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export declare class SlicePipe implements PipeTransform {
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transform(value: any, start: number, end?: number): any;
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transform<T>(value: ReadonlyArray<T>, start: number, end?: number): Array<T>;
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transform(value: string, start: number, end?: number): string;
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transform(value: null, start: number, end?: number): null;
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transform(value: undefined, start: number, end?: number): undefined;
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}
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export declare type Time = {

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