tsc --watch via directory-level fsevents not working on macOS 14.4

[nfarina]

🔎 Search Terms

fsevents tsc watch macOS 14.4 not watching working detecting changes found 0 errors

🕗 Version & Regression Information

• This changed between versions 5.3.3 and 5.4.2 (also occurs in 5.5 dev latest)

⏯ Playground Link

https://gist.github.com/nfarina/d5538d16343830e41c9f3e031a65237e

💻 Code

Reproducible with just this package.json and an arbitrary test.ts file (see Gist link):

{
  "name": "tsc-test",
  "version": "1.0.0",
  "description": "tsc watch problem repro",
  "license": "ISC",
  "scripts": {
    "start": "tsc test.ts --watch"
  },
  "dependencies": {
    "typescript": "^5.4.2"
  }
}

🙁 Actual behavior

This is confusing to me because it seems like many people would be experiencing this right now, but I have tested quite a lot and, for me, TypeScript 5.4.2 broke folder watching completely on my system. (This is a brand new M3 MacBook Air running macOS 14.4).

This works:

"watchFile": "useFsEvents"

And this doesn't:

"watchFile": "useFsEventsOnParentDirectory"

On TypeScript 5.3.3 and below, both work as expected.

🙂 Expected behavior

tsc --watch should observe file changes using fsevents folder watching

Additional information about the issue

I did some digging in the tsc codebase to find where fsevents is being used but was unsuccessful - I'm happy to investigate further if anyone can give me a lead.

[NMinhNguyen]

Just to add an observation: I think this issue is Sonoma specific as watch seems to work on 13.6.4 (Ventura).

[llllvvuu]

When testing this issue, make sure you don't use Vim. Creating/deleting files seems to trigger the file watcher, so it's possible for Vim users to not notice this issue (possibly due to swap files) while VSCode users do.

Consistent repro can be done like:

tsc --watch --watchFile usefseventsonparentdirectory
echo "console.log('Hello world!')" > main.ts
cat main.js
echo "console.log('Hello world 2!')" > main.ts
cat main.js

[llllvvuu]

I found the bisect:

git checkout dc113f8170 // latest `main` as of this post
git revert e40730f
npm run build && npm run build:compiler

I suspect the issue is that the modifiedTime is the modified time of the directory, not the file. At least when I console.log it and compare with stat this seems to be the case, and fileOrDirectory is printing as the directory and only relativeFileName has the file.

[o-alexandrov]

For anyone (like me just now) who stumbles on this, the fix hasn't been released on npm yet in non-next tags.