84 lines
2.5 KiB
TypeScript
84 lines
2.5 KiB
TypeScript
// Copyright 2021 Signal Messenger, LLC
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// SPDX-License-Identifier: AGPL-3.0-only
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import { assert } from 'chai';
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import * as sinon from 'sinon';
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import { map, take } from '../../util/iterables';
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describe('iterable utilities', () => {
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describe('map', () => {
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it('returns an empty iterable when passed an empty iterable', () => {
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const fn = sinon.fake();
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assert.deepEqual([...map([], fn)], []);
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assert.deepEqual([...map(new Set(), fn)], []);
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assert.deepEqual([...map(new Map(), fn)], []);
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sinon.assert.notCalled(fn);
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});
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it('returns a new iterator with values mapped', () => {
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const fn = sinon.fake((n: number) => n * n);
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const result = map([1, 2, 3], fn);
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sinon.assert.notCalled(fn);
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assert.deepEqual([...result], [1, 4, 9]);
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assert.notInstanceOf(result, Array);
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sinon.assert.calledThrice(fn);
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});
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it('iterating doesn\'t "spend" the iterable', () => {
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const result = map([1, 2, 3], n => n * n);
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assert.deepEqual([...result], [1, 4, 9]);
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assert.deepEqual([...result], [1, 4, 9]);
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assert.deepEqual([...result], [1, 4, 9]);
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});
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it('can map over an infinite iterable', () => {
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const everyNumber = {
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*[Symbol.iterator]() {
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for (let i = 0; true; i += 1) {
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yield i;
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}
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},
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};
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const fn = sinon.fake((n: number) => n * n);
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const result = map(everyNumber, fn);
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const iterator = result[Symbol.iterator]();
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assert.deepEqual(iterator.next(), { value: 0, done: false });
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assert.deepEqual(iterator.next(), { value: 1, done: false });
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assert.deepEqual(iterator.next(), { value: 4, done: false });
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assert.deepEqual(iterator.next(), { value: 9, done: false });
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});
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});
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describe('take', () => {
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it('returns the first n elements from an iterable', () => {
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const everyNumber = {
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*[Symbol.iterator]() {
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for (let i = 0; true; i += 1) {
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yield i;
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}
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},
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};
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assert.deepEqual([...take(everyNumber, 0)], []);
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assert.deepEqual([...take(everyNumber, 1)], [0]);
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assert.deepEqual([...take(everyNumber, 7)], [0, 1, 2, 3, 4, 5, 6]);
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});
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it('stops after the iterable has been exhausted', () => {
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const set = new Set([1, 2, 3]);
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assert.deepEqual([...take(set, 3)], [1, 2, 3]);
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assert.deepEqual([...take(set, 4)], [1, 2, 3]);
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assert.deepEqual([...take(set, 10000)], [1, 2, 3]);
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});
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});
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});
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