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feat(helpers)!: use const generics where possible (#2685)
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Lines changed: 165 additions & 21 deletions

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‎docs/guide/upgrading_v9/2685.md‎

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### Usage of TypeScript 5 Features
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_This upgrade is an extension to_ [#1953](./1953.md)
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The helpers module now uses TS5 features, so if you are using Faker with TypeScript, you must use TS5.
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```ts
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// v8
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faker.helpers.arrayElement([1, 2, 3]); // number
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faker.helpers.arrayElement([1, 2, 3] as const); // 1 | 2 | 3
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// v9
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faker.helpers.arrayElement([1, 2, 3]); // 1 | 2 | 3
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```
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If you are unable to upgrade to TS5, you have to keep using Faker v8.

‎package.json‎

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@@ -31,14 +31,7 @@
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"type": "module",
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"main": "dist/index.cjs",
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"module": "dist/index.js",
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"types": "index.d.ts",
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"typesVersions": {
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">=4.0": {
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"*": [
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"dist/types/*"
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]
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}
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},
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"types": "dist/types/index.d.ts",
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"exports": {
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".": {
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"types": "./dist/types/index.d.ts",

‎src/modules/helpers/index.ts‎

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@@ -633,7 +633,7 @@ export class SimpleHelpersModule extends SimpleModuleBase {
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*
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* @since 8.0.0
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*/
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shuffle<T>(
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shuffle<const T>(
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list: T[],
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options: {
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/**
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*
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* @since 2.0.1
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*/
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shuffle<T>(
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shuffle<const T>(
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list: ReadonlyArray<T>,
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options?: {
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/**
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*
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* @since 2.0.1
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*/
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shuffle<T>(
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shuffle<const T>(
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list: T[],
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options?: {
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/**
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inplace?: boolean;
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}
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): T[];
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shuffle<T>(list: T[], options: { inplace?: boolean } = {}): T[] {
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shuffle<const T>(list: T[], options: { inplace?: boolean } = {}): T[] {
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const { inplace = false } = options;
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if (!inplace) {
@@ -734,7 +734,10 @@ export class SimpleHelpersModule extends SimpleModuleBase {
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*
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* @since 6.0.0
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*/
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uniqueArray<T>(source: ReadonlyArray<T> | (() => T), length: number): T[] {
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uniqueArray<const T>(
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source: ReadonlyArray<T> | (() => T),
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length: number
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): T[] {
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if (Array.isArray(source)) {
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const set = new Set<T>(source);
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const array = [...set];
@@ -813,7 +816,7 @@ export class SimpleHelpersModule extends SimpleModuleBase {
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*
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* @since 6.3.0
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*/
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maybe<TResult>(
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maybe<const TResult>(
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callback: () => TResult,
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options: {
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/**
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*
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* @since 6.3.0
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*/
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objectKey<T extends Record<string, unknown>>(object: T): keyof T {
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objectKey<const T extends Record<string, unknown>>(object: T): keyof T {
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const array: Array<keyof T> = Object.keys(object);
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return this.arrayElement(array);
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}
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*
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* @since 6.3.0
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*/
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objectValue<T extends Record<string, unknown>>(object: T): T[keyof T] {
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objectValue<const T extends Record<string, unknown>>(object: T): T[keyof T] {
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const key = this.faker.helpers.objectKey(object);
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return object[key];
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}
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*
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* @since 8.0.0
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*/
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objectEntry<T extends Record<string, unknown>>(
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objectEntry<const T extends Record<string, unknown>>(
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object: T
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): [keyof T, T[keyof T]] {
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const key = this.faker.helpers.objectKey(object);
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*
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* @since 6.3.0
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*/
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arrayElement<T>(array: ReadonlyArray<T>): T {
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arrayElement<const T>(array: ReadonlyArray<T>): T {
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// TODO @xDivisionByZerox 2023-04-20: Remove in v9
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if (array == null) {
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throw new FakerError(
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*
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* @since 8.0.0
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*/
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weightedArrayElement<T>(
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weightedArrayElement<const T>(
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array: ReadonlyArray<{
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/**
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* The weight of the value.
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*
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* @since 6.3.0
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*/
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arrayElements<T>(
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arrayElements<const T>(
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array: ReadonlyArray<T>,
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count?:
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| number
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*
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* @since 8.0.0
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*/
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// This does not use `const T` because enums shouldn't be created on the spot.
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enumValue<T extends Record<string | number, string | number>>(
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enumObject: T
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): T[keyof T] {
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*
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* @since 8.0.0
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*/
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multiple<TResult>(
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multiple<const TResult>(
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method: () => TResult,
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options: {
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/**

‎test/modules/helpers.spec-d.ts‎

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import { describe, expectTypeOf, it } from 'vitest';
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import { faker } from '../../src';
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describe('helpers', () => {
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describe('shuffle', () => {
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describe('inplace: true', () => {
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it('const generic single element', () => {
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const actual = faker.helpers.shuffle([1], { inplace: true });
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expectTypeOf(actual).toEqualTypeOf<Array<1>>();
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});
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it('const generic multiple elements', () => {
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const actual = faker.helpers.shuffle([1, 'a', false], {
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inplace: true,
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});
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expectTypeOf(actual).toEqualTypeOf<Array<1 | 'a' | false>>();
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});
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});
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describe('inplace: false', () => {
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it('const generic single element', () => {
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const actual = faker.helpers.shuffle([1], { inplace: false });
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expectTypeOf(actual).toEqualTypeOf<Array<1>>();
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});
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it('const generic multiple elements', () => {
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const actual = faker.helpers.shuffle([1, 'a', false], {
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inplace: false,
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});
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expectTypeOf(actual).toEqualTypeOf<Array<1 | 'a' | false>>();
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});
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});
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});
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describe('uniqueArray', () => {
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it('const generic single element', () => {
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const actual = faker.helpers.uniqueArray([1], 1);
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expectTypeOf(actual).toEqualTypeOf<Array<1>>();
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});
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it('const generic multiple elements', () => {
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const actual = faker.helpers.uniqueArray([1, 'a', false], 3);
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expectTypeOf(actual).toEqualTypeOf<Array<1 | 'a' | false>>();
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});
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});
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describe('maybe', () => {
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it('const generic single element', () => {
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// TODO @ST-DDT 2024-02-25: Check why this is detected as `number` instead of `1`
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const actual = faker.helpers.maybe(() => 1);
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expectTypeOf(actual).toEqualTypeOf<number | undefined>();
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});
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});
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describe('objectKey', () => {
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it('const generic single element', () => {
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const actual = faker.helpers.objectKey({ a: 1 });
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expectTypeOf(actual).toEqualTypeOf<'a'>();
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});
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it('const generic multiple elements', () => {
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const actual = faker.helpers.objectKey({ a: 1, b: 'a', c: false });
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expectTypeOf(actual).toEqualTypeOf<'a' | 'b' | 'c'>();
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});
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});
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describe('objectValue', () => {
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it('const generic single element', () => {
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const actual = faker.helpers.objectValue({ a: 1 });
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expectTypeOf(actual).toEqualTypeOf<1>();
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});
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it('const generic multiple elements', () => {
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const actual = faker.helpers.objectValue({ a: 1, b: 'a', c: false });
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expectTypeOf(actual).toEqualTypeOf<1 | 'a' | false>();
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});
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});
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describe('objectEntry', () => {
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it('const generic single element', () => {
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const actual = faker.helpers.objectEntry({ a: 1 });
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expectTypeOf(actual).toEqualTypeOf<['a', 1]>();
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});
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it('const generic multiple elements', () => {
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const actual = faker.helpers.objectEntry({ a: 1, b: 'a', c: false });
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// TODO @ST-DDT 2024-02-25: Check whether we can infer the return type any better
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expectTypeOf(actual).toEqualTypeOf<['a' | 'b' | 'c', false | 1 | 'a']>();
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});
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});
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describe('arrayElement', () => {
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it('const generic single element', () => {
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const actual = faker.helpers.arrayElement([1]);
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expectTypeOf(actual).toEqualTypeOf<1>();
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});
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it('const generic multiple elements', () => {
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const actual = faker.helpers.arrayElement([1, 'a', false]);
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expectTypeOf(actual).toEqualTypeOf<1 | 'a' | false>();
101+
});
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});
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describe('arrayElements', () => {
105+
it('const generic single element', () => {
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const actual = faker.helpers.arrayElements([1], 1);
107+
expectTypeOf(actual).toEqualTypeOf<Array<1>>();
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});
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110+
it('const generic multiple elements', () => {
111+
const actual = faker.helpers.arrayElements([1, 'a', false], 3);
112+
expectTypeOf(actual).toEqualTypeOf<Array<1 | 'a' | false>>();
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});
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});
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describe('multiple', () => {
117+
it('const generic single element', () => {
118+
const actual = faker.helpers.multiple(() => 1);
119+
expectTypeOf(actual).toEqualTypeOf<number[]>();
120+
});
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it('const generic multiple elements', () => {
123+
const actual = faker.helpers.multiple(() => 1, { count: 3 });
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expectTypeOf(actual).toEqualTypeOf<number[]>();
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});
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});
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});

‎vitest.config.ts‎

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@@ -19,6 +19,10 @@ export default defineConfig({
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seed: VITEST_SEQUENCE_SEED,
2020
shuffle: true,
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},
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typecheck: {
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enabled: true,
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include: ['test/**/*.spec-d.ts'],
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},
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onConsoleLog(log, type) {
2327
if (
2428
type === 'stderr' &&

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