fs.createWriteStream can cause out-of-order writes, in v18.16+

[dy-dx]

Version

v18.16.0 and up, v19.8.0 and up, v20.x, v21.x

Platform

Darwin x86_64

Subsystem

fs, stream

What steps will reproduce the bug?

const fs = require('fs');

const w = fs.createWriteStream('file.txt');

w.on('open', () => {
  w.write('hello');

  process.nextTick(() => {
    w.write('world');
    w.end();
  });
});

w.on('close', () => {
  console.log(fs.readFileSync('file.txt', 'utf8'));
});

How often does it reproduce? Is there a required condition?

Always

What is the expected behavior? Why is that the expected behavior?

helloworld

What do you see instead?

worldhello

Additional information

The issue was caused by this change: #46818, which landed in node v18.16.0 and v19.8.0.
(Thanks to @Fadorico for tracking down this change. I have also confirmed this by building node locally.)

This is causing the 'unzipper' module to create corrupted files, because its 'fstream' dependency uses fs.createWriteStream() like in the example above.

It looks like when the stream's "open" event fires, the stream does not yet have the "constructed" flag set, so that might be why things are getting weird.

As a workaround, if I wait an additional tick after the "open" event, there are no issues:

w.on('open', () => {
  process.nextTick(() => {
    w.write('hello');

    process.nextTick(() => {
      w.write('world');
      w.end();
    });
  });
});

[benjamingr]

@mcollina @ronag

[mcollina]

I'm sorry it caused a regression this far down. Will patch it. Hopefully we can backport the fix to v18.

[dy-dx]

I can confirm the issue has been fixed in the following node.js versions:

• v18.20.0
• v20.12.0
• v21.7.1