public FileSystemCompletionHelper(
            CompletionListProvider completionProvider,
            TextSpan textChangeSpan,
            ICurrentWorkingDirectoryDiscoveryService fileSystemDiscoveryService,
            Glyph folderGlyph,
            Glyph fileGlyph,
            ImmutableArray<string> searchPaths,
            IEnumerable<string> allowableExtensions,
            Func<string, bool> exclude = null,
            CompletionItemRules itemRules = null)
        {
            Debug.Assert(searchPaths.All(path => PathUtilities.IsAbsolute(path)));

            _completionProvider = completionProvider;
            _textChangeSpan = textChangeSpan;
            _searchPaths = searchPaths;
            _allowableExtensions = allowableExtensions.Select(e => e.ToLowerInvariant()).ToSet();
            _fileSystemDiscoveryService = fileSystemDiscoveryService;
            _folderGlyph = folderGlyph;
            _fileGlyph = fileGlyph;
            _exclude = exclude;
            _itemRules = itemRules;

            _lazyGetDrives = new Lazy<string[]>(() =>
                IOUtilities.PerformIO(Directory.GetLogicalDrives, SpecializedCollections.EmptyArray<string>()));
        }
        public FileSystemCompletionHelper(
            CompletionProvider completionProvider,
            TextSpan textChangeSpan,
            ICurrentWorkingDirectoryDiscoveryService fileSystemDiscoveryService,
            Glyph folderGlyph,
            Glyph fileGlyph,
            ImmutableArray <string> searchPaths,
            IEnumerable <string> allowableExtensions,
            Func <string, bool> exclude   = null,
            CompletionItemRules itemRules = null)
        {
            Debug.Assert(searchPaths.All(path => PathUtilities.IsAbsolute(path)));

            _completionProvider         = completionProvider;
            _textChangeSpan             = textChangeSpan;
            _searchPaths                = searchPaths;
            _allowableExtensions        = allowableExtensions.Select(e => e.ToLowerInvariant()).ToSet();
            _fileSystemDiscoveryService = fileSystemDiscoveryService;
            _folderGlyph                = folderGlyph;
            _fileGlyph = fileGlyph;
            _exclude   = exclude;
            _itemRules = itemRules;

            _lazyGetDrives = new Lazy <string[]>(() =>
                                                 IOUtilities.PerformIO(Directory.GetLogicalDrives, SpecializedCollections.EmptyArray <string>()));
        }