fix(glob): handle glob imports from folders starting with dot

[Copilot]

Glob imports from folders starting with a dot (e.g., ./.foo/test.ts) were failing in development mode with the error:

Failed to resolve import ".foo/test.ts" from "src/main.ts". Does the file exist?

The issue was in the transformGlobImport function where relative import and file paths were not being consistently formatted. When processing a glob pattern like ./.foo/test.ts, the relative path calculation would result in .foo/test.ts. The existing logic only checked if the path started with . to determine whether to add the ./ prefix:

// Before (incorrect):
if (importPath[0] !== '.') importPath = `./${importPath}`
if (filePath[0] !== '.') filePath = `./${filePath}`

Since .foo/test.ts already started with ., it didn't receive the ./ prefix, resulting in an invalid ES module import path that couldn't be resolved.

Fixed by applying the refined condition to all affected patterns:

// After (correct):
if (!importPath.startsWith('./') && !importPath.startsWith('../')) {
  importPath = `./${importPath}`
}
if (!filePath.startsWith('./') && !filePath.startsWith('../')) {
  filePath = `./${filePath}`
}

This ensures proper handling of all relative import patterns:

• Regular paths like foo/bar.ts get the ./ prefix → ./foo/bar.ts
• Paths already with ./ remain unchanged → ./foo/bar.ts
• Parent directory paths ../ are preserved → ../foo/bar.ts (not ./../foo/bar.ts)
• Dot folder paths get the ./ prefix → .foo/bar.ts → ./.foo/bar.ts

Fixed Locations:

• Line 468: importPath handling (original issue)
• Line 461: Virtual modules with base option
• Line 479: Base option handling
• Line 487: Absolute glob handling (always prefix with /)

Testing:

• Added dot folder test case to unit test fixture (packages/vite/src/node/__tests__/plugins/importGlob/fixture-a/.foo/test.ts)
• Added two test cases in fixture-a/index.ts:
  • export const dotFolder = import.meta.glob('./.foo/*.ts', { eager: true }) (tests basic fix)
  • export const dotFolderWithBase = import.meta.glob('./.foo/*.ts', { eager: true, base: './' }) (tests base option fix)
• Updated test snapshots showing all fixes work correctly with generated imports: import * as __vite_glob_XX_0 from "./.foo/test.ts"
• All unit tests pass in both serve and build modes

The fix resolves the dot folder import issue across all code paths while preserving correct ../ path formatting and maintaining full backward compatibility.

Fixes #20788.

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