i.exclude[x.Mod] = true
	}

	return i
}

// modFileIsDirty reports whether the go.mod file differs meaningfully
// from what was indexed.
// If modFile has been changed (even cosmetically) since it was first read,
// modFile.Cleanup must be called before modFileIsDirty.
func (i *modFileIndex) modFileIsDirty(modFile *modfile.File) bool {
	if i == nil {
		return modFile != nil
	}

	if err != nil {
		if errors.Is(err, errNoChange) {
			return nil
		}
		return err
	}

	index := MainModules.GetSingleIndexOrNil()
	dirty := index.modFileIsDirty(modFile)
	if dirty && cfg.BuildMod != "mod" {
		// If we're about to fail due to -mod=readonly,
		// prefer to report a dirty go.mod over a dirty go.sum
		return errGoModDirty
	}