[Group 2] Enable nullable annotations for `Microsoft.Extensions.FileP…

…roviders.Abstractions` (#57405)

* Annotate src

* Annotate ref

* GetFileInfo.subpath is not null

* Update Microsoft.Extensions.FileProviders.Abstractions.cs

* Commit to rerun CI

* Revert "Commit to rerun CI"

This reverts commit 4675f86.

* subpath is non-nullable

src/libraries/Microsoft.Extensions.FileProviders.Abstractions/ref/Microsoft.Extensions.FileProviders.Abstractions.cs

@@ -17,7 +17,7 @@ public partial interface IFileInfo
         System.DateTimeOffset LastModified { get; }
         long Length { get; }
         string Name { get; }
-        string PhysicalPath { get; }
+        string? PhysicalPath { get; }
         System.IO.Stream CreateReadStream();
     }
     public partial interface IFileProvider
@@ -42,7 +42,8 @@ public NotFoundFileInfo(string name) { }
         public System.DateTimeOffset LastModified { get { throw null; } }
         public long Length { get { throw null; } }
         public string Name { get { throw null; } }
-        public string PhysicalPath { get { throw null; } }
+        public string? PhysicalPath { get { throw null; } }
+        [System.Diagnostics.CodeAnalysis.DoesNotReturn]
         public System.IO.Stream CreateReadStream() { throw null; }
     }
     public partial class NullChangeToken : Microsoft.Extensions.Primitives.IChangeToken
@@ -51,7 +52,7 @@ internal NullChangeToken() { }
         public bool ActiveChangeCallbacks { get { throw null; } }
         public bool HasChanged { get { throw null; } }
         public static Microsoft.Extensions.FileProviders.NullChangeToken Singleton { get { throw null; } }
-        public System.IDisposable RegisterChangeCallback(System.Action<object> callback, object state) { throw null; }
+        public System.IDisposable RegisterChangeCallback(System.Action<object?> callback, object? state) { throw null; }
     }
     public partial class NullFileProvider : Microsoft.Extensions.FileProviders.IFileProvider
     {

src/libraries/Microsoft.Extensions.FileProviders.Abstractions/ref/Microsoft.Extensions.FileProviders.Abstractions.csproj

@@ -1,6 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFrameworks>$(NetCoreAppCurrent);netstandard2.0;net461</TargetFrameworks>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
   <ItemGroup>
     <Compile Include="Microsoft.Extensions.FileProviders.Abstractions.cs" />

src/libraries/Microsoft.Extensions.FileProviders.Abstractions/src/IFileInfo.cs

@@ -24,7 +24,7 @@ public interface IFileInfo
         /// <summary>
         /// The path to the file, including the file name. Return null if the file is not directly accessible.
         /// </summary>
-        string PhysicalPath { get; }
+        string? PhysicalPath { get; }
 
         /// <summary>
         /// The name of the file or directory, not including any path.

src/libraries/Microsoft.Extensions.FileProviders.Abstractions/src/Microsoft.Extensions.FileProviders.Abstractions.csproj

@@ -3,6 +3,7 @@
   <PropertyGroup>
     <RootNamespace>Microsoft.Extensions.FileProviders</RootNamespace>
     <TargetFrameworks>$(NetCoreAppCurrent);netstandard2.0;net461</TargetFrameworks>
+    <Nullable>enable</Nullable>
     <EnableDefaultItems>true</EnableDefaultItems>
     <PackageDescription>Abstractions of files and directories.
 

src/libraries/Microsoft.Extensions.FileProviders.Abstractions/src/NotFoundDirectoryContents.cs

@@ -15,7 +15,7 @@ public class NotFoundDirectoryContents : IDirectoryContents
         /// <summary>
         /// A shared instance of <see cref="NotFoundDirectoryContents"/>
         /// </summary>
-        public static NotFoundDirectoryContents Singleton { get; } = new NotFoundDirectoryContents();
+        public static NotFoundDirectoryContents Singleton { get; } = new();
 
         /// <summary>
         /// Always false.

src/libraries/Microsoft.Extensions.FileProviders.Abstractions/src/NotFoundFileInfo.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 
 namespace Microsoft.Extensions.FileProviders
@@ -46,13 +47,14 @@ public NotFoundFileInfo(string name)
         /// <summary>
         /// Always null.
         /// </summary>
-        public string PhysicalPath => null;
+        public string? PhysicalPath => null;
 
         /// <summary>
         /// Always throws. A stream cannot be created for non-existing file.
         /// </summary>
         /// <exception cref="FileNotFoundException">Always thrown.</exception>
         /// <returns>Does not return</returns>
+        [DoesNotReturn]
         public Stream CreateReadStream()
         {
             throw new FileNotFoundException(SR.Format(SR.FileNotExists, Name));

src/libraries/Microsoft.Extensions.FileProviders.Abstractions/src/NullChangeToken.cs

@@ -36,7 +36,7 @@ private NullChangeToken()
         /// <param name="callback">This parameter is ignored</param>
         /// <param name="state">This parameter is ignored</param>
         /// <returns>A disposable object that noops on dispose.</returns>
-        public IDisposable RegisterChangeCallback(Action<object> callback, object state)
+        public IDisposable RegisterChangeCallback(Action<object?> callback, object? state)
         {
             return EmptyDisposable.Instance;
         }