test-stream-map.js

'use strict';

const common = require('../common');
const {
  Readable,
} = require('stream');
const assert = require('assert');
const { once } = require('events');
const { setTimeout } = require('timers/promises');

{
  // Map works on synchronous streams with a synchronous mapper
  const stream = Readable.from([1, 2, 3, 4, 5]).map((x) => x + x);
  (async () => {
    assert.deepStrictEqual(await stream.toArray(), [2, 4, 6, 8, 10]);
  })().then(common.mustCall());
}

{
  // Map works on synchronous streams with an asynchronous mapper
  const stream = Readable.from([1, 2, 3, 4, 5]).map(async (x) => {
    await Promise.resolve();
    return x + x;
  });
  (async () => {
    assert.deepStrictEqual(await stream.toArray(), [2, 4, 6, 8, 10]);
  })().then(common.mustCall());
}

{
  // Map works on asynchronous streams with a asynchronous mapper
  const stream = Readable.from([1, 2, 3, 4, 5]).map(async (x) => {
    return x + x;
  }).map((x) => x + x);
  (async () => {
    assert.deepStrictEqual(await stream.toArray(), [4, 8, 12, 16, 20]);
  })().then(common.mustCall());
}

{
  // Map works on an infinite stream
  const stream = Readable.from(async function* () {
    while (true) yield 1;
  }()).map(common.mustCall(async (x) => {
    return x + x;
  }, 5));
  (async () => {
    let i = 1;
    for await (const item of stream) {
      assert.strictEqual(item, 2);
      if (++i === 5) break;
    }
  })().then(common.mustCall());
}

{
  // Map works on non-objectMode streams
  const stream = new Readable({
    read() {
      this.push(Uint8Array.from([1]));
      this.push(Uint8Array.from([2]));
      this.push(null);
    }
  }).map(async ([x]) => {
    return x + x;
  }).map((x) => x + x);
  const result = [4, 8];
  (async () => {
    for await (const item of stream) {
      assert.strictEqual(item, result.shift());
    }
  })().then(common.mustCall());
}

{
  // Does not care about data events
  const source = new Readable({
    read() {
      this.push(Uint8Array.from([1]));
      this.push(Uint8Array.from([2]));
      this.push(null);
    }
  });
  setImmediate(() => stream.emit('data', Uint8Array.from([1])));
  const stream = source.map(async ([x]) => {
    return x + x;
  }).map((x) => x + x);
  const result = [4, 8];
  (async () => {
    for await (const item of stream) {
      assert.strictEqual(item, result.shift());
    }
  })().then(common.mustCall());
}

{
  // Emitting an error during `map`
  const stream = Readable.from([1, 2, 3, 4, 5]).map(async (x) => {
    if (x === 3) {
      stream.emit('error', new Error('boom'));
    }
    return x + x;
  });
  assert.rejects(
    stream.map((x) => x + x).toArray(),
    /boom/,
  ).then(common.mustCall());
}

{
  // Throwing an error during `map` (sync)
  const stream = Readable.from([1, 2, 3, 4, 5]).map((x) => {
    if (x === 3) {
      throw new Error('boom');
    }
    return x + x;
  });
  assert.rejects(
    stream.map((x) => x + x).toArray(),
    /boom/,
  ).then(common.mustCall());
}


{
  // Throwing an error during `map` (async)
  const stream = Readable.from([1, 2, 3, 4, 5]).map(async (x) => {
    if (x === 3) {
      throw new Error('boom');
    }
    return x + x;
  });
  assert.rejects(
    stream.map((x) => x + x).toArray(),
    /boom/,
  ).then(common.mustCall());
}

{
  // Concurrency + AbortSignal
  const ac = new AbortController();
  const range = Readable.from([1, 2, 3, 4, 5]);
  const stream = range.map(common.mustCall(async (_, { signal }) => {
    await once(signal, 'abort');
    throw signal.reason;
  }, 2), { signal: ac.signal, concurrency: 2 });
  // pump
  assert.rejects(async () => {
    for await (const item of stream) {
      assert.fail('should not reach here, got ' + item);
    }
  }, {
    name: 'AbortError',
  }).then(common.mustCall());

  setImmediate(() => {
    ac.abort();
  });
}

{
  // Concurrency result order
  const stream = Readable.from([1, 2]).map(async (item, { signal }) => {
    await setTimeout(10 - item, { signal });
    return item;
  }, { concurrency: 2 });

  (async () => {
    const expected = [1, 2];
    for await (const item of stream) {
      assert.strictEqual(item, expected.shift());
    }
  })().then(common.mustCall());
}

{
  // Error cases
  assert.throws(() => Readable.from([1]).map(1), /ERR_INVALID_ARG_TYPE/);
  assert.throws(() => Readable.from([1]).map((x) => x, {
    concurrency: 'Foo'
  }), /ERR_OUT_OF_RANGE/);
  assert.throws(() => Readable.from([1]).map((x) => x, 1), /ERR_INVALID_ARG_TYPE/);
}
{
  // Test result is a Readable
  const stream = Readable.from([1, 2, 3, 4, 5]).map((x) => x);
  assert.strictEqual(stream.readable, true);
}