Make nullable enabled by default across entire repo (#6960)

Author: zivkan

build/Shared/EncodingUtility.cs

@@ -1,8 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#nullable enable
-
 namespace NuGet.Shared
 {
     internal static class EncodingUtility

build/Shared/EqualityUtility.cs

@@ -1,8 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#nullable enable
-
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;

build/Shared/SimplePool.cs

@@ -1,8 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#nullable enable
-
 using System;
 using System.Collections.Generic;
 

build/Shared/StringBuilderPool.cs

@@ -1,8 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
-#nullable enable
-
 using System.Text;
 
 namespace NuGet

build/Shared/TaskResult.cs

@@ -1,15 +1,15 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 
 namespace NuGet;
 
-#nullable enable
-
 internal static class TaskResult
 {
     /// <summary>

build/Shared/TaskResultCache.cs

@@ -1,7 +1,5 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
-#nullable enable
-
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;

build/Shared/Utf8JsonReaderExtensions.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Text.Json;
 

build/Shared/Utf8JsonStreamReader.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Buffers;
 using System.Collections.Generic;

build/common.project.props

@@ -51,6 +51,7 @@
     <NoWarn Condition="'$(DotNetBuildSourceOnly)' == 'true'">$(NoWarn);CS1998;CA1416;CS0618;CS1574</NoWarn>
     <SuppressTfmSupportBuildWarnings>true</SuppressTfmSupportBuildWarnings>
     <DisableImplicitNuGetFallbackFolder>true</DisableImplicitNuGetFallbackFolder>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <!-- Defaults -->

src/NuGet.Clients/NuGet.CommandLine/CommandLineParser.cs

@@ -1,6 +1,8 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+#nullable disable
+
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;