existsSync is expensive

[arcanis]

• Version: master
• Platform: n/a
• Subsystem: fs

The current implementation of fs.existsSync involves wrapping accessSync in a try/catch statement. While conceptually simple, it has one fundamental flaw: it means that Node has to instance an Error for each call to fs.existsSync made on non-existing paths. This can end up very expensive.

Would it be possible to make this function more lightweight by simply checking the return value of the libuv's access call? I'm not familiar with the Node internals, but I feel like simply returning false instead of calling handleErrorFromBinding here would be sufficient.

Relevant lines:

node/lib/fs.js

Lines 229 to 236 in e35f671

	function existsSync(path) {
	try {
	fs.accessSync(path, F_OK);
	return true;
	} catch (e) {
	return false;
	}
	}

[arcanis]

On a related note, I wonder if Node should have a tryStat function that would simply return null when an error happens (to also avoid creating this Error object).

[joyeecheung]

This was added in d3955d1 from a glance I think it should be alright to call the binding and handle it directly instead of using the public fs.accessSync

[jdalton]

V8 now supports optional catch bindings so the e can just be omitted.

[arcanis]

Yep but it will still be constructed, right? In handleErrorFromBinding

[arcanis]

Opened a PR to fix this - 10x faster 🎉

#24068

[arcanis]

Errata: I didn't saw that @joyeecheung had already opened #24015 😃