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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.