Implement the _.hidden File Attributes on Windows

Windows has a specific attribute to mark a file as hidden as opposed to
prefixing ".". This allows setting and getting the attribute.

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 +410,6 @@ open class FileManager : NSObject {
                         newAccessDate = providedDate
                     }
                     #endif
-                    
                 case .immutable: fallthrough
                 case ._userImmutable:
                     prepareToSetOrUnsetFlag(UF_IMMUTABLE)
@@ -418,7 +421,21 @@ open class FileManager : NSObject {
                     prepareToSetOrUnsetFlag(UF_APPEND)
 
                 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
                     prepareToSetOrUnsetFlag(UF_HIDDEN)
+#endif
 
                 // FIXME: On Darwin, these can be set with setattrlist(); and of course chown/chgrp on other OSes.
                 case .ownerAccountID: fallthrough
@@ -537,7 +554,8 @@ 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)
@@ -572,6 +590,11 @@ open class FileManager : NSObject {
             result[.appendOnly] = NSNumber(value: true)
         }
 #endif
+
+#if os(Windows)
+        let attrs = attributes.dwFileAttributes
+        result[._hidden] = attrs & DWORD(FILE_ATTRIBUTE_HIDDEN) != 0
+#endif
         result[.ownerAccountID] = NSNumber(value: UInt64(s.st_uid))
         result[.groupOwnerAccountID] = NSNumber(value: UInt64(s.st_gid))
 

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 +557,31 @@ 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)'")
         }
 
+        var resourceValues = URLResourceValues()
+        resourceValues.isHidden = true
+        for filename in [ hiddenItem1, hiddenItem2, hiddenItem3, hiddenItem4] {
+            XCTAssertTrue(fm.createFile(atPath: filename, contents: Data(), attributes: nil), "Cant create file '\(filename)'")
+            do {
+                var url = URL(fileURLWithPath: filename)
+                try url.setResourceValues(resourceValues)
+            } catch {
+                XCTFail("Couldn't make \(filename) a hidden file")
+            }
+        }
+
+        do {
+            var hiddenURL1 = URL(fileURLWithPath: hiddenDir1)
+            var hiddenURL2 = URL(fileURLWithPath: hiddenDir2)
+            try hiddenURL1.setResourceValues(resourceValues)
+            try hiddenURL2.setResourceValues(resourceValues)
+        } 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 {