Types issues in v4 ?

[dperetti]

Describe the bug

Just upgraded my project from v 3.6 to v4. Worked without hassle, but some type definitions seem to be broken in v4.

Versions:

• Chokidar version 4.02
• Typescript 5.7.3

To Reproduce:

const watcher = chokidar.watch(watchedPaths, {
        persistent: true,
        useFsEvents: true, // 👈 Typescript Error: useFsEvents does not exist in type
        usePolling: false,
        ignoreInitial: true,
        disableGlobbing: true
      })
      //👇 TS2576: Property on does not exist on type FSWatcher. Did you mean to access the static member FSWatcher. on instead?
      .on('change', (f, stats) => {
              log.info(`File ${f} changed. root: (${sourceFullPath})`)
            })

[dperetti]

Ok just figured out it's related to #1392 . But why was it closed?

[43081j]

as per the last comment in that thread, that person's problem was because we hadn't published the type constraint yet

so unless you also haven't updated to latest 4.x, that issue is unrelated and has correctly been closed

useFsEvents isn't an option anymore, as we don't use fs events. i see there are some remnants of it in the readme, we should remove those.

if removing that doesn't help, let me know. it could be that you need to npm up @types/node but not sure why that'd be the case

[JoshuaHintze]

I'm seeing the same problem.

	"chokidar": "^4.0.3",
	"@types/node": "20.11.20",
	"typescript": "^5.6.3",

               import chokidar, { type FSWatcher } from 'chokidar'; // Tried with and without FSWatcher import

		const watcher: FSWatcher = chokidar.watch(this.inboxPath, {
			persistent: true,
			ignoreInitial: false,
			ignored: (path, stats) => {
				if (stats && stats.isFile()) {
					return !path.endsWith('.json');
				}
				return false;
			}
		});
		
               // ERROR HERE: Property 'on' does not exist on type 'FSWatcher'. Did you mean to access the static member 'FSWatcher.on' instead?ts(2576)

		watcher.on('add', async (filePath) => { console.log('File added: ' + filePath); });

[43081j]

Which doesn't make much sense since it always had an on method before and after the type changes

Can you tell us exactly which versions it installed? (npm ls @types/node)

And when you mouse over watcher or something in your editor, what is it?

If you jump to the definition of FSWatcher in your editor, what is the first line? (The class declaration)

[JoshuaHintze]

Here are some screen shots.

When I go to definition I get this.

FS Watcher file and first line

Using @types/node 20.11.20

FYI - and maybe this is the culprit. I'm using pnpm and not npm or yarn.

[dperetti]

if removing that doesn't help, let me know. it could be that you need to npm up @types/node but not sure why that'd be the case

Thank you, indeed my @types/node was outdated! 🫢

It's now working fine with @types/node 22.10.10 .

[43081j]

Yep the same for you @JoshuaHintze , the version of @types/node you have is before they added a type parameter to EventEmitter it seems

If you update that, it'll probably work fine

[JoshuaHintze]

Thanks @43081j - I'm curious doesn't @types/node 22.X.X mean you are using node 22 LTS? If we are actually using Node 20.X.X wouldn't that be an issuse,

Or perhaps you are saying that they typedef maintainers missed a key piece that has always been in there? What is the min requirement for v4 chokidar?

[43081j]

It's purely a types thing so it doesn't align to a version of node. Since node had event emitters (long ago), this was the correct type. At some point they fixed the types but that is nothing to do with any particular node support

In JavaScript, the class has existed for a very long time and hasn't changed much. The types improved separately to better define it

I'm not sure how the DT contributors deal with their versions. In most DT packages, the version is nothing to do with the source package version. With the node types though, I'm not sure. You may have to go ask the node DT contributors