fix(importMetaGlob): throw early for relative glob patterns in virtual modules

[DoriAlagem]

Fixes #22345.

Problem

When a plugin produces a virtual module that calls import.meta.glob with a relative pattern (e.g. './*.js'), Vite silently returns {} instead of throwing the documented error:

In virtual modules, all globs must start with '/'

The existing check inside resolvePaths is only reached when matched files are iterated. If the relative pattern matches no files (or matches files that are then filtered out), resolvePaths is never called — so the error is never thrown and the caller gets an empty object with no diagnostic.

Minimal repro:

// vite plugin
load(id) {
  if (id === '\0foo') return `export default import.meta.glob('./*.js')`
}

modules is {} with no warning or error logged.

Fix

Add an early guard immediately before the glob() call. If the module is virtual (!dir), the pattern is relative (isRelative), and no base option is set, throw the same error message that already exists further down in resolvePaths. This ensures the user gets a clear diagnostic regardless of whether any files happen to match the broken pattern.

[DoriAlagem]

Hey @bluwy — just a gentle ping on this one! It's been about a week since opening. Happy to make any adjustments if needed.

[sapphi-red]

Would you fix the test failure?

[sapphi-red]

closing as #22497 is merged