TSServer doesn't respect watchOptions for watchFile

[gluxon]

This seems to be intentional, but it looks like TSServer always uses fixed polling to watch files regardless of editor configured options.

The relevant code was written 4.5 years ago. Does the TypeScript team plan on revisiting that decision? If not, should the watchFile option have its choices limited to reduce confusion? (I understand that will partly be a VSCode issue if the answer is yes.)

Personally I think it's strange that this is configurable in tsc but not tsserver.

---

Technical Details:

Here's the watchUtilities.ts call, which passes a WatchOptions arg:

TypeScript/src/compiler/watchUtilities.ts

Line 440 in 4885dec

watchFile: (file, callback, pollingInterval, options) => host.watchFile(file, callback, pollingInterval, options),

TypeScript/src/compiler/types.ts

Lines 5844 to 5853 in 4885dec

	export interface WatchOptions {
	watchFile?: WatchFileKind;
	watchDirectory?: WatchDirectoryKind;
	fallbackPolling?: PollingWatchKind;
	synchronousWatchDirectory?: boolean;
	excludeDirectories?: string[];
	excludeFiles?: string[];
	[option: string]: CompilerOptionsValue | undefined;
	}

Here's the implemention in tsserver, which actually overrides the default implementation and ignores the options arg.

TypeScript/src/tsserver/server.ts

Lines 885 to 890 in 4885dec

	sys.watchFile = (fileName, callback) => {
	const watchedFile = pollingWatchedFileSet.addFile(fileName, callback);
	return {
	close: () => pollingWatchedFileSet.removeFile(watchedFile)
	};
	};

tsserver.log also reports a watchFile option of 3 (WatchFileKind.UseFsEvents), which is incorrect.

Info 40   [19:45:41.986] FileWatcher:: Added:: WatchInfo: /Volumes/git/TypeScript/src/server/types.ts 500 {"watchFile":3,"watchDirectory":0} Project:  WatchType: Closed Script info

TypeScript Version: v4.2.0-dev.20201112

Search Terms:

• tsserver polling

Steps to Reproduce

Add the following to VSCode settings.json:

{
  "typescript.tsserver.watchOptions": {
    "watchFile": "useFsEvents",
  }
}

Expected behavior:

• TSServer watches files through FSEvents.
• Updates to watched source files happen almost immediately.

Actual behavior:

• TSServer watches files with fixed polling.

[gluxon]

@zhengbli Apologies if you're no longer involved with TypeScript, but if you have a moment I'm curious if it was intentional for this to be non-configurable in tsserver (but configurable in tsc).

[gluxon]

This affects language service plugins that provide typings for imported files.

mrmckeb/typescript-plugin-css-modules#95

To summarize, I'm trying to set up CSS type checks but not seeing updates happen until 7+ minutes later due to tsserver's polling watch being slow.

[dko-slapdash]

What an awesome improvement would it be at least on MacOS VSCode! We currently wait for 20-40 seconds after a git pull for some files to be typechecked properly in VSCode. I made an experiment, manually commented out the code @gluxon mentioned above right in tsserver.js:

and it made VSCode pickup changes within several seconds.

[ericjeney]

@sheetalkamat Do you have any updates on whether this is something that the TypeScript team is interested in accepting a fix for? This is the only thing blocking my team from adding type-safety to the last untyped piece of our codebase (CSS modules).

[sheetalkamat]

This is scheduled for 4.2.1

[gluxon]

@sheetalkamat Thanks! 🎉