`--watch` mode does not work on volumes mounted via `/etc/synthetic.conf`

[millerick]

Version

v18.15.0

Platform

Darwin BL-mmillerick-NNH946444W 22.3.0 Darwin Kernel Version 22.3.0: Thu Jan 5 20:48:54 PST 2023; root:xnu-8792.81.2~2/RELEASE_ARM64_T6000 arm64

Subsystem

No response

What steps will reproduce the bug?

I am using a Mac. I have the following entry in /etc/synthetic.conf to create a folder in my root directory where I house all of my source code repositories.

src     System/Volumes/Data/src

After mounting a directory in this fashion, create /src/experiment.js with the following contents:

setInterval(() => { console.log('output') }, 1000)

Then begin running it with node --watch /src/experiment.js. Separately run touch /src/experiment.js and observe that the reload does not happen.

If instead you do the above, but replace /src/experiment.js with ~/experiment.js, the reload happens as expected.

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

Always

What is the expected behavior?

I would expect node --watch to work in any directory, and always produce output like

Restarting '/Users/mmillerick/experiment.js'
output
output

What do you see instead?

Instead I do not see reloads happening.

Additional information

No response

[bnoordhuis]

Does fs.watch() work on that directory? If not, you have the answer to why reloads don't work: the operating system doesn't report events.

[mikrosystheme]

The issue must be with --watch because fs.watch() works reliably on those paths.

[millerick]

Does fs.watch() work on that directory? If not, you have the answer to why reloads don't work: the operating system doesn't report events.

Creating ~/experiment2.js and /src/experiment2.js with the following contents results in the expected behavior in both directories.

const fs = require('fs');

fs.watch('experiment2.js', () => console.log('file touched'));

setTimeout(() => {}, 1000000);

I will also add that TypeScript's watch mode works in projects that I have in my /src directory (probably because it relies on fs.watch somewhere). I haven't had the time to look through the differences in implementation and see if there is the possibility for me to apply some type of fix to Node. Maybe I will find time over the weekend.