deno/tests/unit_node/stream_test.ts

// Copyright 2018-2025 the Deno authors. MIT license.

import { assert, assertEquals } from "@std/assert";
import { fromFileUrl, relative } from "@std/path";
import { finished, pipeline } from "node:stream/promises";
import { getDefaultHighWaterMark, Stream, Writable } from "node:stream";
import { TextEncoderStream } from "node:stream/web";
import { createReadStream, createWriteStream } from "node:fs";
import { EventEmitter } from "node:events";

Deno.test("stream/promises pipeline", async () => {
  const filePath = relative(
    Deno.cwd(),
    fromFileUrl(new URL("./testdata/lorem_ipsum.txt", import.meta.url)),
  );
  const input = createReadStream(filePath);
  const output = createWriteStream("lorem_ipsum.txt.copy");

  await pipeline(input, output);

  const content = Deno.readTextFileSync("lorem_ipsum.txt.copy");
  assert(content.startsWith("Lorem ipsum dolor sit amet"));
  try {
    Deno.removeSync("lorem_ipsum.txt.copy");
  } catch {
    // pass
  }
});

Deno.test("stream getDefaultHighWaterMark", () => {
  assertEquals(
    getDefaultHighWaterMark(false),
    Deno.build.os === "windows" ? 16 * 1024 : 64 * 1024,
  );
  assertEquals(getDefaultHighWaterMark(true), 16);
});

Deno.test("stream is an instance of EventEmitter", () => {
  const stream = new Stream();
  assert(stream instanceof EventEmitter);
});

Deno.test("finished on web streams", async () => {
  const stream = new ReadableStream({
    start(controller) {
      controller.enqueue("asd");
      controller.close();
    },
  });
  const promise = finished(stream as unknown as NodeJS.ReadableStream);
  for await (const chunk of stream) {
    assertEquals(chunk, "asd");
  }
  await promise;
});

// https://github.com/denoland/deno/issues/28905
Deno.test("Writable toWeb", async () => {
  const nodeWritable = new Writable({
    write(_chunk, _encoding, callback) {
      // Simulate the issue by delaying the callback slightly
      setTimeout(() => {
        callback();
      }, 10);
    },
  });

  const webWritable = Writable.toWeb(nodeWritable);

  const source = ["line1", "line2", "line3"];
  const readable = ReadableStream.from(source);

  await readable
    // @ts-ignore wrong types
    .pipeThrough(new TextEncoderStream())
    // @ts-ignore wrong types
    .pipeTo(webWritable);

  await finished(nodeWritable);
});