[Foundation] Several fixes to NSFileManager. (#18371)

* Enable nullability.
* Add API that was previously iOS-specific to all platforms.

src/Foundation/NSFileManager.cs

@@ -26,11 +26,15 @@
 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 //
 //
+using CoreFoundation;
 using ObjCRuntime;
+
 using System;
 using System.Runtime.InteropServices;
 using System.Runtime.Versioning;
 
+#nullable enable
+
 namespace Foundation {
 
 	// This is a convenience enum around a set of native strings.
@@ -57,15 +61,15 @@ public class NSFileAttributes {
 		public bool? AppendOnly { get; set; }
 		public bool? Busy { get; set; }
 		public bool? ExtensionHidden { get; set; }
-		public NSDate CreationDate { get; set; }
-		public string OwnerAccountName { get; set; }
-		public string GroupOwnerAccountName { get; set; }
+		public NSDate? CreationDate { get; set; }
+		public string? OwnerAccountName { get; set; }
+		public string? GroupOwnerAccountName { get; set; }
 		public nint? SystemNumber { get; set; } // NSInteger
 		public nuint? DeviceIdentifier { get; set; } // unsigned long
 		public nuint? GroupOwnerAccountID { get; set; } // unsigned long
 
 		public bool? Immutable { get; set; }
-		public NSDate ModificationDate { get; set; }
+		public NSDate? ModificationDate { get; set; }
 		public nuint? OwnerAccountID { get; set; } // unsigned long
 		public nuint? HfsCreatorCode { get; set; }
 		public nuint? HfsTypeCode { get; set; } // unsigned long
@@ -83,7 +87,7 @@ public class NSFileAttributes {
 		internal NSDictionary ToDictionary ()
 		{
 			NSFileType? type;
-			NSString v = null;
+			NSString? v = null;
 			var dict = new NSMutableDictionary ();
 			if (AppendOnly.HasValue)
 				dict.SetObject (NSNumber.FromBoolean (AppendOnly.Value), NSFileManager.AppendOnly);
@@ -158,7 +162,8 @@ internal NSDictionary ToDictionary ()
 				case NSFileProtection.CompleteUntilFirstUserAuthentication:
 					v = NSFileManager.FileProtectionCompleteUntilFirstUserAuthentication; break;
 				}
-				dict.SetObject (v, NSFileManager.FileProtectionKey);
+				if (v is not null)
+					dict.SetObject (v, NSFileManager.FileProtectionKey);
 			}
 #endif
 			return dict;
@@ -222,7 +227,7 @@ internal NSDictionary ToDictionary ()
 		}
 		#endregion
 
-		public static NSFileAttributes FromDictionary (NSDictionary dict)
+		public static NSFileAttributes? FromDictionary (NSDictionary dict)
 		{
 			if (dict is null)
 				return null;
@@ -247,9 +252,7 @@ public static NSFileAttributes FromDictionary (NSDictionary dict)
 			ret.SystemFileNumber = fetch_nuint (dict, NSFileManager.SystemFileNumber);
 			ret.Size = fetch_ulong (dict, NSFileManager.Size);
 
-			NSString name;
-
-			name = dict.ObjectForKey (NSFileManager.NSFileType) as NSString;
+			var name = dict.ObjectForKey (NSFileManager.NSFileType) as NSString;
 			if (name is not null) {
 				NSFileType? type = null;
 
@@ -314,7 +317,7 @@ internal NSFileSystemAttributes (NSDictionary dict)
 		// "The value corresponds to the value of st_dev, as returned by stat(2)" => st_dev is defined to be int32_t in all architectures.
 		public uint Number { get; internal set; }
 
-		internal static NSFileSystemAttributes FromDictionary (NSDictionary dict)
+		internal static NSFileSystemAttributes? FromDictionary (NSDictionary dict)
 		{
 			if (dict is null)
 				return null;
@@ -341,108 +344,99 @@ public partial class NSFileManager {
 		[DllImport (Constants.FoundationLibrary)]
 		static extern IntPtr NSUserName ();
 
-		public static string UserName {
+		public static string? UserName {
 			get {
-				using (var nsstring = ObjCRuntime.Runtime.GetNSObject<NSString> (NSUserName ()))
-					return nsstring.ToString ();
+				return CFString.FromHandle (NSUserName ());
 			}
 		}
 
 		[DllImport (Constants.FoundationLibrary)]
 		static extern IntPtr NSFullUserName ();
 
-		public static string FullUserName {
+		public static string? FullUserName {
 			get {
-				using (var nsstring = ObjCRuntime.Runtime.GetNSObject<NSString> (NSFullUserName ()))
-					return nsstring.ToString ();
+				return CFString.FromHandle (NSFullUserName ());
 			}
 		}
 
 		[DllImport (Constants.FoundationLibrary)]
 		static extern IntPtr NSHomeDirectory ();
 
-		public static string HomeDirectory {
+		public static string? HomeDirectory {
 			get {
-				using (var nsstring = ObjCRuntime.Runtime.GetNSObject<NSString> (NSHomeDirectory ()))
-					return nsstring.ToString ();
+				return CFString.FromHandle (NSHomeDirectory ());
 			}
 		}
 
 		[DllImport (Constants.FoundationLibrary)]
 		static extern IntPtr NSHomeDirectoryForUser (/* NSString */IntPtr userName);
 
-		public static string GetHomeDirectory (string userName)
+		public static string? GetHomeDirectory (string userName)
 		{
 			if (userName is null)
 				throw new ArgumentNullException (nameof (userName));
 
-			using (var nsstring = new NSString (userName))
-			using (var homeDir = ObjCRuntime.Runtime.GetNSObject<NSString> (NSHomeDirectoryForUser (nsstring.GetHandle ())))
-				return homeDir.ToString ();
+			var userNamePtr = CFString.CreateNative (userName);
+			var rv = CFString.FromHandle (NSHomeDirectoryForUser (userNamePtr));
+			CFString.ReleaseNative (userNamePtr);
+			return rv;
 		}
 
 		[DllImport (Constants.FoundationLibrary)]
 		static extern IntPtr NSTemporaryDirectory ();
 
-		public static string TemporaryDirectory {
+		public static string? TemporaryDirectory {
 			get {
-				using (var nsstring = ObjCRuntime.Runtime.GetNSObject<NSString> (NSTemporaryDirectory ()))
-					return nsstring.ToString ();
+				return CFString.FromHandle (NSTemporaryDirectory ());
 			}
 		}
 
 		public bool SetAttributes (NSFileAttributes attributes, string path, out NSError error)
 		{
 			if (attributes is null)
-				throw new ArgumentNullException ("attributes");
+				throw new ArgumentNullException (nameof (attributes));
 			return SetAttributes (attributes.ToDictionary (), path, out error);
 		}
 
 		public bool SetAttributes (NSFileAttributes attributes, string path)
 		{
 			if (attributes is null)
-				throw new ArgumentNullException ("attributes");
+				throw new ArgumentNullException (nameof (attributes));
 
 			return SetAttributes (attributes.ToDictionary (), path, out _);
 		}
 
-		public bool CreateDirectory (string path, bool createIntermediates, NSFileAttributes attributes, out NSError error)
+		public bool CreateDirectory (string path, bool createIntermediates, NSFileAttributes? attributes, out NSError error)
 		{
-			var dict = attributes is null ? null : attributes.ToDictionary ();
-			return CreateDirectory (path, createIntermediates, dict, out error);
+			return CreateDirectory (path, createIntermediates, attributes?.ToDictionary (), out error);
 		}
 
-		public bool CreateDirectory (string path, bool createIntermediates, NSFileAttributes attributes)
+		public bool CreateDirectory (string path, bool createIntermediates, NSFileAttributes? attributes)
 		{
-			NSError error;
-			var dict = attributes is null ? null : attributes.ToDictionary ();
-			return CreateDirectory (path, createIntermediates, dict, out error);
+			return CreateDirectory (path, createIntermediates, attributes?.ToDictionary (), out var _);
 		}
 
-		public bool CreateFile (string path, NSData data, NSFileAttributes attributes)
+		public bool CreateFile (string path, NSData data, NSFileAttributes? attributes)
 		{
-			var dict = attributes is null ? null : attributes.ToDictionary ();
-			return CreateFile (path, data, dict);
+			return CreateFile (path, data, attributes?.ToDictionary ());
 		}
 
-		public NSFileAttributes GetAttributes (string path, out NSError error)
+		public NSFileAttributes? GetAttributes (string path, out NSError error)
 		{
 			return NSFileAttributes.FromDictionary (_GetAttributes (path, out error));
 		}
 
-		public NSFileAttributes GetAttributes (string path)
+		public NSFileAttributes? GetAttributes (string path)
 		{
-			NSError error;
-			return NSFileAttributes.FromDictionary (_GetAttributes (path, out error));
+			return NSFileAttributes.FromDictionary (_GetAttributes (path, out var _));
 		}
 
-		public NSFileSystemAttributes GetFileSystemAttributes (string path)
+		public NSFileSystemAttributes? GetFileSystemAttributes (string path)
 		{
-			NSError error;
-			return NSFileSystemAttributes.FromDictionary (_GetFileSystemAttributes (path, out error));
+			return NSFileSystemAttributes.FromDictionary (_GetFileSystemAttributes (path, out var _));
 		}
 
-		public NSFileSystemAttributes GetFileSystemAttributes (string path, out NSError error)
+		public NSFileSystemAttributes? GetFileSystemAttributes (string path, out NSError error)
 		{
 			return NSFileSystemAttributes.FromDictionary (_GetFileSystemAttributes (path, out error));
 		}
@@ -458,5 +452,32 @@ public string CurrentDirectory {
 			// ignore boolean return value
 			set { ChangeCurrentDirectory (value); }
 		}
+
+		public static NSError SetSkipBackupAttribute (string filename, bool skipBackup)
+		{
+			if (filename is null)
+				throw new ArgumentNullException (nameof (filename));
+
+			using (var url = NSUrl.FromFilename (filename)) {
+				url.SetResource (NSUrl.IsExcludedFromBackupKey, (NSNumber) (skipBackup ? 1 : 0), out var error);
+				return error;
+			}
+		}
+
+		public static bool GetSkipBackupAttribute (string filename)
+		{
+			return GetSkipBackupAttribute (filename, out var _);
+		}
+
+		public static bool GetSkipBackupAttribute (string filename, out NSError error)
+		{
+			if (filename is null)
+				throw new ArgumentNullException (nameof (filename));
+
+			using (var url = NSUrl.FromFilename (filename)) {
+				url.TryGetResource (NSUrl.IsExcludedFromBackupKey, out var value, out error);
+				return (error is null) && ((long) ((NSNumber) value) == 1);
+			}
+		}
 	}
 }

src/frameworks.sources

@@ -821,7 +821,6 @@ FOUNDATION_SOURCES = \
 	Foundation/NSFastEnumerationState.cs \
 	Foundation/NSFastEnumerator.cs \
 	Foundation/NSFileManager.cs \
-	Foundation/NSFileManager.iOS.cs \
 	Foundation/NSFileManagerDelegate.cs \
 	Foundation/NSFormatter.cs \
 	Foundation/NSHost.cs \

tests/monotouch-test/Foundation/FileManagerTest.cs

@@ -85,8 +85,6 @@ public void GetUrlForUbiquityContainer ()
 				// aborting is evil, so don't bother aborting the thread, just let it run its course
 			}
 		}
-		//GetSkipBackupAttribute doesn't exist on Mac
-#if !MONOMAC
 
 		[Test]
 		public void GetSkipBackupAttribute ()
@@ -113,7 +111,6 @@ public void GetSkipBackupAttribute ()
 				File.Delete (filename);
 			}
 		}
-#endif
 
 		[Test]
 		public void DefaultManager ()