inference-spec.ts

import '../iterablehelpers';
import '../asynciterablehelpers.js';
import { PassThrough } from 'stream';
import { of } from 'ix/iterable/index.js';
import { map } from 'ix/iterable/operators/index.node.js';

const TEST_DOM_STREAMS = process.env.TEST_DOM_STREAMS === 'true';
const TEST_NODE_STREAMS = process.env.TEST_NODE_STREAMS === 'true';

describe('Iterable type inference', () => {
  test('#pipe type inference is correct with one operator', () => {
    const source = of(0, 1, 2).pipe(map((x) => x + 1));
    expect(source).toEqualStream([1, 2, 3]);
  });
  test('#pipe type inference is correct with two operators', () => {
    const source = of(0, 1, 2).pipe(
      map((x) => x + 1),
      map((x) => x + 1)
    );
    expect(source).toEqualStream([2, 3, 4]);
  });

  if (TEST_NODE_STREAMS) {
    test('#pipe type inference is correct with writable stream', () => {
      const source = of(0, 1, 2).pipe(new PassThrough({ objectMode: true }));
      expect(source).toEqualStream([0, 1, 2]);
    });
    test('#pipe type inference is correct with writable stream and pipe options', () => {
      const source = of(0, 1, 2).pipe(new PassThrough({ objectMode: true }), { end: true });
      expect(source).toEqualStream([0, 1, 2]);
    });
  }

  if (TEST_DOM_STREAMS) {
    test('#pipeThrough type inference is correct with writable stream', () => {
      const source = of(0, 1, 2).pipeThrough(new TransformStream<number, number>());
      expect(source).toEqualStream([0, 1, 2]);
    });
    test('#pipeThrough type inference is correct with writable stream and pipe options', () => {
      const source = of(0, 1, 2).pipeThrough(new TransformStream<number, number>(), {
        preventClose: false,
      });
      expect(source).toEqualStream([0, 1, 2]);
    });
  }
});