Add a .hidden file attribute

Windows has a specific attribute to mark a file as hidden as opposed to
prefixing ".". This allows setting and getting the attribute. On POSIX,
it will return based on the "." prefix and setting it does nothing.

Author: gmittert

Foundation/FileManager.swift

@@ -13,6 +13,10 @@ internal func &(left: UInt32, right: mode_t) -> mode_t {
 }
 #endif
 
+#if os(Windows)
+import MSVCRT
+#endif
+
 #if !canImport(Darwin) && !os(FreeBSD)
 // The values do not matter as long as they are nonzero.
 fileprivate let UF_IMMUTABLE: Int32 = 1
@@ -406,7 +410,22 @@ open class FileManager : NSObject {
                         newAccessDate = providedDate
                     }
                     #endif
-                    
+                case .hidden:
+#if os(Windows)
+                    let attrs = try windowsFileAttributes(atPath: path).dwFileAttributes
+                    guard let isHidden = attributeValues[attribute] as? Bool else {
+                      fatalError("Can't set \(attribute) to \(attributeValues[attribute] as Any?)")
+                    }
+
+                    let hiddenAttrs = isHidden
+                        ? attrs | DWORD(FILE_ATTRIBUTE_HIDDEN)
+                        : attrs & DWORD(bitPattern: ~FILE_ATTRIBUTE_HIDDEN)
+                    guard path.withCString(encodedAs: UTF16.self, { SetFileAttributesW($0, hiddenAttrs) }) else {
+                        fatalError("Couldn't set \(path) to be hidden")
+                    }
+#else
+                    break
+#endif
                 case .immutable: fallthrough
                 case ._userImmutable:
                     prepareToSetOrUnsetFlag(UF_IMMUTABLE)
@@ -537,7 +556,8 @@ open class FileManager : NSObject {
 
 #if os(Windows)
         result[.deviceIdentifier] = NSNumber(value: UInt64(s.st_rdev))
-        let type = FileAttributeType(attributes: try windowsFileAttributes(atPath: path), atPath: path)
+        let attributes = try windowsFileAttributes(atPath: path)
+        let type = FileAttributeType(attributes: attributes, atPath: path)
 #else
         if let pwd = getpwuid(s.st_uid), pwd.pointee.pw_name != nil {
             let name = String(cString: pwd.pointee.pw_name)
@@ -553,6 +573,13 @@ open class FileManager : NSObject {
 #endif
         result[.type] = type
 
+#if os(Windows)
+        let attrs = attributes.dwFileAttributes
+        result[.hidden] = attrs & DWORD(FILE_ATTRIBUTE_HIDDEN) != 0
+#else
+        result[.hidden] = path.first == "."
+#endif
+
         if type == .typeBlockSpecial || type == .typeCharacterSpecial {
             result[.deviceIdentifier] = NSNumber(value: UInt64(s.st_rdev))
         }
@@ -1143,6 +1170,7 @@ public struct FileAttributeKey : RawRepresentable, Equatable, Hashable {
     public static let extensionHidden = FileAttributeKey(rawValue: "NSFileExtensionHidden")
     public static let hfsCreatorCode = FileAttributeKey(rawValue: "NSFileHFSCreatorCode")
     public static let hfsTypeCode = FileAttributeKey(rawValue: "NSFileHFSTypeCode")
+    public static let hidden = FileAttributeKey(rawValue: "NSFileHidden")
     public static let immutable = FileAttributeKey(rawValue: "NSFileImmutable")
     public static let appendOnly = FileAttributeKey(rawValue: "NSFileAppendOnly")
     public static let creationDate = FileAttributeKey(rawValue: "NSFileCreationDate")
@@ -1169,6 +1197,7 @@ public struct FileAttributeKey : RawRepresentable, Equatable, Hashable {
         .extensionHidden,
         .hfsCreatorCode,
         .hfsTypeCode,
+        .hidden,
         .immutable,
         .appendOnly,
         .creationDate,

TestFoundation/TestFileManager.swift

@@ -496,11 +496,13 @@ class TestFileManager : XCTestCase {
     func test_directoryEnumerator() {
         let fm = FileManager.default
         let basePath = NSTemporaryDirectory() + "testdir\(NSUUID().uuidString)/"
-        let subDirs1 = basePath + "subdir1/subdir2/.hiddenDir/subdir3/"
+        let hiddenDir1 = basePath + "subdir1/subdir2/.hiddenDir/"
+        let subDirs1 = hiddenDir1 + "subdir3/"
         let itemPath1 = basePath + "itemFile1"
 #if os(Windows)
         // Filenames ending with '.' are not valid on Windows, so don't bother testing them
-        let subDirs2 = basePath + "subdir1/subdir2/subdir4.app/subdir5/.subdir6.ext/subdir7.ext/"
+        let hiddenDir2 = basePath + "subdir1/subdir2/subdir4.app/subdir5/.subdir6.ext/"
+        let subDirs2 = hiddenDir2 + "subdir7.ext/"
         let itemPath2 = subDirs1 + "itemFile2"
         let itemPath3 = subDirs1 + "itemFile3.ext"
 #else
@@ -555,10 +557,26 @@ class TestFileManager : XCTestCase {
 
         XCTAssertNotNil(try? fm.createDirectory(atPath: subDirs1, withIntermediateDirectories: true, attributes: nil))
         XCTAssertNotNil(try? fm.createDirectory(atPath: subDirs2, withIntermediateDirectories: true, attributes: nil))
-        for filename in [itemPath1, itemPath2, itemPath3, hiddenItem1, hiddenItem2, hiddenItem3, hiddenItem4] {
+        for filename in [itemPath1, itemPath2, itemPath3] {
             XCTAssertTrue(fm.createFile(atPath: filename, contents: Data(), attributes: nil), "Cant create file '\(filename)'")
         }
 
+        for filename in [ hiddenItem1, hiddenItem2, hiddenItem3, hiddenItem4] {
+            XCTAssertTrue(fm.createFile(atPath: filename, contents: Data(), attributes: nil), "Cant create file '\(filename)'")
+            do {
+                try fm.setAttributes([.hidden: true], ofItemAtPath: filename)
+            } catch {
+                XCTFail("Couldn't make \(filename) a hidden file")
+            }
+        }
+
+        do {
+            try fm.setAttributes([.hidden: true], ofItemAtPath: hiddenDir1)
+            try fm.setAttributes([.hidden: true], ofItemAtPath: hiddenDir2)
+        } catch {
+            XCTFail("Couldn't make \(hiddenDir1) and \(hiddenDir2) hidden directories")
+        }
+
         if let foundItems = directoryItems(options: []) {
             XCTAssertEqual(foundItems.count, fileLevels.count)
             for (name, level) in foundItems {