Slow unocss config loading since v0.59.0

[hi-ogawa]

UnoCSS version

0.60.2

Describe the bug

I was seeing slower startup when integrating unocss in a recent project and it looks like this is happening since v0.59.0.
It might not be noticeable on a decent PC, but I happen to be (temporary) using a worst laptop and this felt like a significant slow down (for exampele, from 608.85ms to 2.020s in a stackblitz reproduction below).

I briefly checked perf from node --inspect-brk repro.mjs and it appears that jiti (used by unconfig, which in turn used by @unocss/config) is taking a long time transforming something. I'm suspecting this might be because jiti is transforming entire unocss after it became esm only.

Show screenshot of performance devtools

Reproduction

https://github.com/hi-ogawa/reproductions/tree/main/unocss-jiti-esm-slow-config
https://stackblitz.com/github/hi-ogawa/reproductions/tree/main/unocss-jiti-esm-slow-config?file=repro.mjs

// node repro.mjs
import { loadConfig } from "@unocss/config";

console.time("[loadConfig]");
console.log(await loadConfig());
console.timeEnd("[loadConfig]");

$ npm install && (node repro.mjs && (cd fast && npm i && node repro.mjs))
... on v0.60.2 ...
{
  config: {},
  sources: [ '/home/projects/qgnigvkoz.github/uno.config.ts' ]
}
[loadConfig]: 2.020s

... on v0.58.9 ...
{
  config: {},
  sources: [ '/home/projects/qgnigvkoz.github/fast/uno.config.ts' ]
}
[loadConfig]: 608.85ms

System Info

(stackblitz)

Validations

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• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
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• The provided reproduction is a minimal reproducible example of the bug.

[userquin]

On my latpop also reproducible (i7 12700H):

• v0.58.9: [loadConfig]: 889.937ms
• v0.60.2: [loadConfig]: 1.620s

[userquin]

@hi-ogawa you can provide cwd and file name when loading the configuration: await loadConfig(process.cwd(), 'unocss.config.ts'):

• v0.58.9: [loadConfig]: 225.94ms
• v0.60.2: [loadConfig]: 664.644ms

[userquin]

Using in the reproductions (preparing PR):

	"overrides": {
		"unconfig": "0.4.1"
	}

• v0.58.9: [loadConfig]: 215.667ms
• v0.60.2: [loadConfig]: 203.762ms