fix(css): fix lightningcss dep url resolution with custom root

[hi-ogawa]

Description

• closes Relative CSS asset import does not work with root config set #18117

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[sapphi-red]

I pushed a commit that renames root dir to dir dir because root dir has a special meaning and the test wasn't actually testing the issue.

vite/playground/vitestSetup.ts

Lines 138 to 140 in 993d45b

	// when `root` dir is present, use it as vite's root
	const testCustomRoot = path.resolve(testDir, 'root')
	rootDir = fs.existsSync(testCustomRoot) ? testCustomRoot : testDir

[sapphi-red]

Sorry, I think I just mixed things up. The first code was correct. 😅

[hi-ogawa]

I pushed a commit that renames root dir to dir dir because root dir has a special meaning and the test wasn't actually testing the issue.

Aha, I didn't notice that. I initially used playground/css-lightningcss/root with a separate config vite.config-root.ts dceaaf3 , but things got broken, so I just moved it off to a separate playground css-lightningcss-root.