Annotate System.IO.FileSystem for nullable

src/libraries/Common/src/Interop/Windows/Kernel32/Interop.ReplaceFile.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
 using System;
 using System.IO;
 using System.Runtime.InteropServices;
@@ -12,11 +13,11 @@ internal partial class Kernel32
     {
         [DllImport(Libraries.Kernel32, EntryPoint = "ReplaceFileW", SetLastError = true, CharSet = CharSet.Unicode, BestFitMapping = false)]
         private static extern bool ReplaceFilePrivate(
-            string replacedFileName, string replacementFileName, string backupFileName,
+            string replacedFileName, string replacementFileName, string? backupFileName,
             int dwReplaceFlags, IntPtr lpExclude, IntPtr lpReserved);
 
         internal static bool ReplaceFile(
-            string replacedFileName, string replacementFileName, string backupFileName,
+            string replacedFileName, string replacementFileName, string? backupFileName,
             int dwReplaceFlags, IntPtr lpExclude, IntPtr lpReserved)
         {
             replacedFileName = PathInternal.EnsureExtendedPrefixIfNeeded(replacedFileName);

src/libraries/Common/src/System/IO/FileSystem.Attributes.Windows.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
 using Microsoft.Win32.SafeHandles;
 using System;
 using System.Collections.Generic;
@@ -18,12 +19,12 @@ namespace System.IO
 {
     internal static partial class FileSystem
     {
-        public static bool DirectoryExists(string fullPath)
+        public static bool DirectoryExists(string? fullPath)
         {
             return DirectoryExists(fullPath, out int lastError);
         }
 
-        private static bool DirectoryExists(string path, out int lastError)
+        private static bool DirectoryExists(string? path, out int lastError)
         {
             Interop.Kernel32.WIN32_FILE_ATTRIBUTE_DATA data = default;
             lastError = FillAttributeInfo(path, ref data, returnErrorOnNotFound: true);
@@ -52,7 +53,7 @@ public static bool FileExists(string fullPath)
         /// <param name="path">The file path from which the file attribute information will be filled.</param>
         /// <param name="data">A struct that will contain the attribute information.</param>
         /// <param name="returnErrorOnNotFound">Return the error code for not found errors?</param>
-        internal static int FillAttributeInfo(string path, ref Interop.Kernel32.WIN32_FILE_ATTRIBUTE_DATA data, bool returnErrorOnNotFound)
+        internal static int FillAttributeInfo(string? path, ref Interop.Kernel32.WIN32_FILE_ATTRIBUTE_DATA data, bool returnErrorOnNotFound)
         {
             int errorCode = Interop.Errors.ERROR_SUCCESS;
 
@@ -97,7 +98,7 @@ internal static int FillAttributeInfo(string path, ref Interop.Kernel32.WIN32_FI
                         // cases that we know we don't want to retry on.
 
                         Interop.Kernel32.WIN32_FIND_DATA findData = default;
-                        using (SafeFindHandle handle = Interop.Kernel32.FindFirstFile(path, ref findData))
+                        using (SafeFindHandle handle = Interop.Kernel32.FindFirstFile(path!, ref findData))
                         {
                             if (handle.IsInvalid)
                             {

src/libraries/Common/src/System/IO/FileSystem.DirectoryCreation.Windows.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
 using Microsoft.Win32.SafeHandles;
 using System;
 using System.Collections.Generic;
@@ -18,7 +19,7 @@ namespace System.IO
 {
     internal static partial class FileSystem
     {
-        public static unsafe void CreateDirectory(string fullPath, byte[] securityDescriptor = null)
+        public static unsafe void CreateDirectory(string fullPath, byte[]? securityDescriptor = null)
         {
             // We can save a bunch of work if the directory we want to create already exists.  This also
             // saves us in the case where sub paths are inaccessible (due to ERROR_ACCESS_DENIED) but the
@@ -126,7 +127,7 @@ public static unsafe void CreateDirectory(string fullPath, byte[] securityDescri
             // Handle CreateDirectory("X:\\") when X: doesn't exist. Similarly for n/w paths.
             if ((count == 0) && !somepathexists)
             {
-                string root = Path.GetPathRoot(fullPath);
+                string? root = Path.GetPathRoot(fullPath);
 
                 if (!DirectoryExists(root))
                 {

src/libraries/Common/src/System/Text/ValueUtf8Converter.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
 using System.Buffers;
 
 namespace System.Text
@@ -13,7 +14,7 @@ namespace System.Text
     /// </summary>
     internal ref struct ValueUtf8Converter
     {
-        private byte[] _arrayToReturnToPool;
+        private byte[]? _arrayToReturnToPool;
         private Span<byte> _bytes;
 
         public ValueUtf8Converter(Span<byte> initialBuffer)
@@ -40,7 +41,7 @@ public Span<byte> ConvertAndTerminateString(ReadOnlySpan<char> value)
 
         public void Dispose()
         {
-            byte[] toReturn = _arrayToReturnToPool;
+            byte[]? toReturn = _arrayToReturnToPool;
             if (toReturn != null)
             {
                 _arrayToReturnToPool = null;

src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.cs

@@ -24,7 +24,7 @@ public static void Delete(string path, bool recursive) { }
         public static System.Collections.Generic.IEnumerable<string> EnumerateFileSystemEntries(string path, string searchPattern) { throw null; }
         public static System.Collections.Generic.IEnumerable<string> EnumerateFileSystemEntries(string path, string searchPattern, System.IO.EnumerationOptions enumerationOptions) { throw null; }
         public static System.Collections.Generic.IEnumerable<string> EnumerateFileSystemEntries(string path, string searchPattern, System.IO.SearchOption searchOption) { throw null; }
-        public static bool Exists(string path) { throw null; }
+        public static bool Exists(string? path) { throw null; }
         public static System.DateTime GetCreationTime(string path) { throw null; }
         public static System.DateTime GetCreationTimeUtc(string path) { throw null; }
         public static string GetCurrentDirectory() { throw null; }
@@ -46,7 +46,7 @@ public static void Delete(string path, bool recursive) { }
         public static System.DateTime GetLastWriteTime(string path) { throw null; }
         public static System.DateTime GetLastWriteTimeUtc(string path) { throw null; }
         public static string[] GetLogicalDrives() { throw null; }
-        public static System.IO.DirectoryInfo GetParent(string path) { throw null; }
+        public static System.IO.DirectoryInfo? GetParent(string path) { throw null; }
         public static void Move(string sourceDirName, string destDirName) { }
         public static void SetCreationTime(string path, System.DateTime creationTime) { }
         public static void SetCreationTimeUtc(string path, System.DateTime creationTimeUtc) { }
@@ -61,7 +61,7 @@ public sealed partial class DirectoryInfo : System.IO.FileSystemInfo
         public DirectoryInfo(string path) { }
         public override bool Exists { get { throw null; } }
         public override string Name { get { throw null; } }
-        public System.IO.DirectoryInfo Parent { get { throw null; } }
+        public System.IO.DirectoryInfo? Parent { get { throw null; } }
         public System.IO.DirectoryInfo Root { get { throw null; } }
         public void Create() { }
         public System.IO.DirectoryInfo CreateSubdirectory(string path) { throw null; }
@@ -111,10 +111,10 @@ public static void AppendAllLines(string path, System.Collections.Generic.IEnume
         public static void AppendAllLines(string path, System.Collections.Generic.IEnumerable<string> contents, System.Text.Encoding encoding) { }
         public static System.Threading.Tasks.Task AppendAllLinesAsync(string path, System.Collections.Generic.IEnumerable<string> contents, System.Text.Encoding encoding, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static System.Threading.Tasks.Task AppendAllLinesAsync(string path, System.Collections.Generic.IEnumerable<string> contents, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
-        public static void AppendAllText(string path, string contents) { }
-        public static void AppendAllText(string path, string contents, System.Text.Encoding encoding) { }
-        public static System.Threading.Tasks.Task AppendAllTextAsync(string path, string contents, System.Text.Encoding encoding, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
-        public static System.Threading.Tasks.Task AppendAllTextAsync(string path, string contents, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
+        public static void AppendAllText(string path, string? contents) { }
+        public static void AppendAllText(string path, string? contents, System.Text.Encoding encoding) { }
+        public static System.Threading.Tasks.Task AppendAllTextAsync(string path, string? contents, System.Text.Encoding encoding, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
+        public static System.Threading.Tasks.Task AppendAllTextAsync(string path, string? contents, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static System.IO.StreamWriter AppendText(string path) { throw null; }
         public static void Copy(string sourceFileName, string destFileName) { }
         public static void Copy(string sourceFileName, string destFileName, bool overwrite) { }
@@ -125,7 +125,7 @@ public static void Copy(string sourceFileName, string destFileName, bool overwri
         public static void Decrypt(string path) { }
         public static void Delete(string path) { }
         public static void Encrypt(string path) { }
-        public static bool Exists(string path) { throw null; }
+        public static bool Exists(string? path) { throw null; }
         public static System.IO.FileAttributes GetAttributes(string path) { throw null; }
         public static System.DateTime GetCreationTime(string path) { throw null; }
         public static System.DateTime GetCreationTimeUtc(string path) { throw null; }
@@ -153,8 +153,8 @@ public static void Move(string sourceFileName, string destFileName, bool overwri
         public static System.Threading.Tasks.Task<string> ReadAllTextAsync(string path, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static System.Collections.Generic.IEnumerable<string> ReadLines(string path) { throw null; }
         public static System.Collections.Generic.IEnumerable<string> ReadLines(string path, System.Text.Encoding encoding) { throw null; }
-        public static void Replace(string sourceFileName, string destinationFileName, string destinationBackupFileName) { }
-        public static void Replace(string sourceFileName, string destinationFileName, string destinationBackupFileName, bool ignoreMetadataErrors) { }
+        public static void Replace(string sourceFileName, string destinationFileName, string? destinationBackupFileName) { }
+        public static void Replace(string sourceFileName, string destinationFileName, string? destinationBackupFileName, bool ignoreMetadataErrors) { }
         public static void SetAttributes(string path, System.IO.FileAttributes fileAttributes) { }
         public static void SetCreationTime(string path, System.DateTime creationTime) { }
         public static void SetCreationTimeUtc(string path, System.DateTime creationTimeUtc) { }
@@ -170,16 +170,16 @@ public static void WriteAllLines(string path, string[] contents) { }
         public static void WriteAllLines(string path, string[] contents, System.Text.Encoding encoding) { }
         public static System.Threading.Tasks.Task WriteAllLinesAsync(string path, System.Collections.Generic.IEnumerable<string> contents, System.Text.Encoding encoding, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static System.Threading.Tasks.Task WriteAllLinesAsync(string path, System.Collections.Generic.IEnumerable<string> contents, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
-        public static void WriteAllText(string path, string contents) { }
-        public static void WriteAllText(string path, string contents, System.Text.Encoding encoding) { }
-        public static System.Threading.Tasks.Task WriteAllTextAsync(string path, string contents, System.Text.Encoding encoding, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
-        public static System.Threading.Tasks.Task WriteAllTextAsync(string path, string contents, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
+        public static void WriteAllText(string path, string? contents) { }
+        public static void WriteAllText(string path, string? contents, System.Text.Encoding encoding) { }
+        public static System.Threading.Tasks.Task WriteAllTextAsync(string path, string? contents, System.Text.Encoding encoding, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
+        public static System.Threading.Tasks.Task WriteAllTextAsync(string path, string? contents, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
     }
     public sealed partial class FileInfo : System.IO.FileSystemInfo
     {
         public FileInfo(string fileName) { }
-        public System.IO.DirectoryInfo Directory { get { throw null; } }
-        public string DirectoryName { get { throw null; } }
+        public System.IO.DirectoryInfo? Directory { get { throw null; } }
+        public string? DirectoryName { get { throw null; } }
         public override bool Exists { get { throw null; } }
         public bool IsReadOnly { get { throw null; } set { } }
         public long Length { get { throw null; } }
@@ -200,8 +200,8 @@ public void MoveTo(string destFileName, bool overwrite) { }
         public System.IO.FileStream OpenRead() { throw null; }
         public System.IO.StreamReader OpenText() { throw null; }
         public System.IO.FileStream OpenWrite() { throw null; }
-        public System.IO.FileInfo Replace(string destinationFileName, string destinationBackupFileName) { throw null; }
-        public System.IO.FileInfo Replace(string destinationFileName, string destinationBackupFileName, bool ignoreMetadataErrors) { throw null; }
+        public System.IO.FileInfo Replace(string destinationFileName, string? destinationBackupFileName) { throw null; }
+        public System.IO.FileInfo Replace(string destinationFileName, string? destinationBackupFileName, bool ignoreMetadataErrors) { throw null; }
         public override string ToString() { throw null; }
     }
     public abstract partial class FileSystemInfo : System.MarshalByRefObject, System.Runtime.Serialization.ISerializable
@@ -266,19 +266,19 @@ public ref partial struct FileSystemEntry
     }
     public partial class FileSystemEnumerable<TResult> : System.Collections.Generic.IEnumerable<TResult>, System.Collections.IEnumerable
     {
-        public FileSystemEnumerable(string directory, System.IO.Enumeration.FileSystemEnumerable<TResult>.FindTransform transform, System.IO.EnumerationOptions options = null) { }
-        public System.IO.Enumeration.FileSystemEnumerable<TResult>.FindPredicate ShouldIncludePredicate { get { throw null; } set { } }
-        public System.IO.Enumeration.FileSystemEnumerable<TResult>.FindPredicate ShouldRecursePredicate { get { throw null; } set { } }
+        public FileSystemEnumerable(string directory, System.IO.Enumeration.FileSystemEnumerable<TResult>.FindTransform transform, System.IO.EnumerationOptions? options = null) { }
+        public System.IO.Enumeration.FileSystemEnumerable<TResult>.FindPredicate? ShouldIncludePredicate { get { throw null; } set { } }
+        public System.IO.Enumeration.FileSystemEnumerable<TResult>.FindPredicate? ShouldRecursePredicate { get { throw null; } set { } }
         public System.Collections.Generic.IEnumerator<TResult> GetEnumerator() { throw null; }
         System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() { throw null; }
         public delegate bool FindPredicate(ref System.IO.Enumeration.FileSystemEntry entry);
         public delegate TResult FindTransform(ref System.IO.Enumeration.FileSystemEntry entry);
     }
     public abstract partial class FileSystemEnumerator<TResult> : System.Runtime.ConstrainedExecution.CriticalFinalizerObject, System.Collections.Generic.IEnumerator<TResult>, System.Collections.IEnumerator, System.IDisposable
     {
-        public FileSystemEnumerator(string directory, System.IO.EnumerationOptions options = null) { }
+        public FileSystemEnumerator(string directory, System.IO.EnumerationOptions? options = null) { }
         public TResult Current { get { throw null; } }
-        object System.Collections.IEnumerator.Current { get { throw null; } }
+        object? System.Collections.IEnumerator.Current { get { throw null; } }
         protected virtual bool ContinueOnError(int error) { throw null; }
         public void Dispose() { }
         protected virtual void Dispose(bool disposing) { }
@@ -293,6 +293,6 @@ public static partial class FileSystemName
     {
         public static bool MatchesSimpleExpression(System.ReadOnlySpan<char> expression, System.ReadOnlySpan<char> name, bool ignoreCase = true) { throw null; }
         public static bool MatchesWin32Expression(System.ReadOnlySpan<char> expression, System.ReadOnlySpan<char> name, bool ignoreCase = true) { throw null; }
-        public static string TranslateWin32Expression(string expression) { throw null; }
+        public static string TranslateWin32Expression(string? expression) { throw null; }
     }
 }

src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.csproj

@@ -1,6 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <Configurations>netcoreapp-Debug;netcoreapp-Release</Configurations>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="System.IO.FileSystem.cs" />

src/libraries/System.IO.FileSystem/src/System.IO.FileSystem.csproj

@@ -5,6 +5,7 @@
     <NoWarn>$(NoWarn);CS1573</NoWarn>
     <IsPartialFacadeAssembly>true</IsPartialFacadeAssembly>
     <Configurations>netcoreapp-Unix-Debug;netcoreapp-Unix-Release;netcoreapp-Windows_NT-Debug;netcoreapp-Windows_NT-Release</Configurations>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
   <PropertyGroup Condition="'$(TargetsUnix)' == 'true'">
     <NoWarn>$(NoWarn);414</NoWarn>