Node: fs.watch() consistently claims a file in a similarly named directory also changed

[Krinkle]

• Version: Latest versions of Current and LTS releases: v11.6.0, v10.15.0, v8.15.0, v6.16.0.
• Platform: macOS
• Subsystem: fs

Description

When using fs.watch() to watch several directories, and changing a file with either fs.writeFileSync or fs.appendFileSync, an unrelated FSWatcher for a similarly named directory is getting an event.

Test case

Code at https://github.com/Krinkle/sandbox/blob/node-fs-watch/test.js.

Build output at https://travis-ci.com/Krinkle/sandbox/jobs/167573963.

In brief:

1. The file system looks as follows:

    - home/
          - a/
             - file1
          - b/
             - file1
             - file2
          - bb/
             - file1

1. Using fs.watch( .., { encoding: 'utf8', recursive: false }) an FSWatcher is created for home/a, home/b and home/bb.

2. A modification is made to home/bb/file1.

Expected

An event relating to home/bb/file1 (file) and/or home/bb (directory).

Actual

Two events:

• change home/b/file1
• change home/bb/file1

... modifying home/bb/file1
home/b [change: UNEXPECTED] rename /file1
home/bb [change: expected] rename file1

It is consistently happening in this way on both Travis CI and for myself locally. It has confused me for a quite a while, and I am at a loss as to why this is happening. It seems to specifically result in an event for the same name in a similarly named directory.

It never fires for a or for file2. Rather, bb/file1 always misfires for b/file1.

[Trott]

Any chance you've tried running this on Linux or Windows or anything else on Travis CI or elsewhere? I'm curious if it's macOS-only or not.

[Krinkle]

Yep, I've got 11 sibling jobs on the same Travis build, for other environments 😃

https://travis-ci.com/Krinkle/sandbox/builds/95971463

os:
 - linux
 - osx
 - windows
node_js:
 - 11
 - 10
 - 8
 - 6

The behaviour is the same across Node.js versions.

Linux:

• event for home/bb/file1

Windows:

• event for home/bb
• event for home/bb/file1

macOS:

• event for home/b/file1 ❓
• event for home/bb/file1

It appears specific to macOS, and not specific to Travis CI; as I'm seeing the same problem on my workstation (MacBook, Node.js 10 from Homebrew, nonvirtualised).

[Trott]

@nodejs/fs @nodejs/platform-macos

[bnoordhuis]

I'm > 50% confident that https://github.com/libuv/libuv/pull/2082 fixes this.

[targos]

I'm closing this as fixed in libuv 1.25.0. Please reopen if it's not the case.