Add FileAttributes.None

src/libraries/System.IO.FileSystem.Primitives/tests/FileAttributesTests.cs

@@ -11,6 +11,7 @@ public static class FileAttributesTests
         [Fact]
         public static void ValueTest()
         {
+            Assert.Equal(0x0000, (int)FileAttributes.None);
             Assert.Equal(0x0001, (int)FileAttributes.ReadOnly);
             Assert.Equal(0x0002, (int)FileAttributes.Hidden);
             Assert.Equal(0x0004, (int)FileAttributes.System);

src/libraries/System.IO.FileSystem/tests/File/GetSetAttributes_SafeFileHandle.cs

@@ -22,7 +22,7 @@ protected override FileAttributes GetAttributes(string path)
             using SafeFileHandle fileHandle = OpenFileHandle(path, FileAccess.Read);
             return File.GetAttributes(fileHandle);
         }
-        
+
         protected override void SetAttributes(string path, FileAttributes attributes)
         {
             using SafeFileHandle fileHandle = OpenFileHandle(path, FileAccess.ReadWrite);
@@ -33,7 +33,7 @@ protected override void SetAttributes(string path, FileAttributes attributes)
         public void NullArgumentValidation()
         {
             Assert.Throws<ArgumentNullException>("fileHandle", static () => File.GetAttributes(default(SafeFileHandle)!));
-            Assert.Throws<ArgumentNullException>("fileHandle", static () => File.SetAttributes(default(SafeFileHandle)!, (FileAttributes)0));
+            Assert.Throws<ArgumentNullException>("fileHandle", static () => File.SetAttributes(default(SafeFileHandle)!, FileAttributes.None));
         }
     }
 }

src/libraries/System.Private.CoreLib/src/System/IO/Enumeration/FileSystemEnumerator.Unix.cs

@@ -129,7 +129,7 @@ public bool MoveNext()
                             }
                         }
 
-                        if (!isSpecialDirectory && _options.AttributesToSkip != 0)
+                        if (!isSpecialDirectory && _options.AttributesToSkip != FileAttributes.None)
                         {
                             // entry.IsHidden and entry.IsReadOnly will hit the disk if the caches had not been
                             // initialized yet and we could not soft-retrieve the attributes in Initialize

src/libraries/System.Private.CoreLib/src/System/IO/FileAttributes.cs

@@ -6,6 +6,7 @@ namespace System.IO
     [Flags]
     public enum FileAttributes
     {
+        None = 0x0000,
         ReadOnly = 0x0001,
         Hidden = 0x0002,
         System = 0x0004,

src/libraries/System.Runtime/ref/System.Runtime.cs

@@ -9746,6 +9746,7 @@ public enum FileAccess
     [System.FlagsAttribute]
     public enum FileAttributes
     {
+        None = 0,
         ReadOnly = 1,
         Hidden = 2,
         System = 4,

src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/EnumConverterTests.cs

@@ -186,8 +186,8 @@ public void ConvertFileAttributes(bool useGenericVariant)
                 options);
             Assert.Equal(@"""directory, compressed, integrity_stream""", json);
 
-            json = JsonSerializer.Serialize(FileAttributes.Compressed & FileAttributes.Device, options);
-            Assert.Equal(@"0", json);
+            json = JsonSerializer.Serialize((FileAttributes)(-1), options);
+            Assert.Equal(@"-1", json);
 
             json = JsonSerializer.Serialize(FileAttributes.Directory & FileAttributes.Compressed | FileAttributes.IntegrityStream, options);
             Assert.Equal(@"""integrity_stream""", json);