30 lines
735 B
TypeScript
30 lines
735 B
TypeScript
import assert from 'node:assert/strict';
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import test from 'node:test';
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import type { Result } from '../src/result.ts';
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function parse(input: string): Result<{ value: number }> {
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const value = Number(input);
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if (Number.isNaN(value)) return { err: new Error('not a number') };
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return { value };
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}
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test('destructuring a result narrows on err', () => {
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const { err, value } = parse('42');
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if (err) {
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assert.fail('should have parsed');
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}
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// Fails to compile if narrowing does not remove undefined from value.
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assert.equal(value.toFixed(0), '42');
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});
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test('a failed result carries err and nothing else', () => {
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const { err, value } = parse('nope');
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assert.ok(err instanceof Error);
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assert.equal(value, undefined);
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});
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