Enable nullable ref types

src/Directory.Build.props

@@ -6,6 +6,7 @@
     <BaseOutputPath Condition=" '$(BaseOutputPath)' == '' ">$(RepoRootPath)bin\$(MSBuildProjectName)\</BaseOutputPath>
     <PackageOutputPath>$(RepoRootPath)bin\Packages\$(Configuration)\NuGet\</PackageOutputPath>
     <LangVersion>8.0</LangVersion>
+    <Nullable>enable</Nullable>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <UpdateXlfOnBuild Condition=" '$(UpdateXlfOnBuild)' == '' ">true</UpdateXlfOnBuild>
 
@@ -27,10 +28,11 @@
 
   <ItemGroup>
     <PackageReference Include="MicroBuild.VisualStudio" Version="$(MicroBuildPackageVersion)" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.Net.Compilers.Toolset" Version="3.4.0-beta2-final" PrivateAssets="all" />
     <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.0-preview.2" PrivateAssets="all" />
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0-beta2-19367-01" PrivateAssets="All" />
     <PackageReference Include="Nerdbank.GitVersioning" Version="3.0.25" PrivateAssets="all" />
-    <PackageReference Include="StyleCop.Analyzers" Version="1.1.118" PrivateAssets="all" />
+    <PackageReference Include="StyleCop.Analyzers" Version="1.2.0-beta.66" PrivateAssets="all" />
   </ItemGroup>
   <ItemGroup>
     <None Include="$(MSBuildThisFileDirectory)PackageIcon.png" Pack="true" PackagePath="" />

src/StreamJsonRpc.Tests/CommonErrorDataTests.cs

@@ -17,7 +17,7 @@ public CommonErrorDataTests(ITestOutputHelper logger)
     [Fact]
     public void Ctor_CopyFrom_Null()
     {
-        Assert.Throws<ArgumentNullException>(() => new CommonErrorData(null));
+        Assert.Throws<ArgumentNullException>(() => new CommonErrorData(null!));
     }
 
     [Fact]

src/StreamJsonRpc.Tests/CommonMethodNameTransformsTests.cs

@@ -14,7 +14,7 @@ public void CamelCase()
         Assert.Equal("fireOne", CommonMethodNameTransforms.CamelCase("fireOne"));
         Assert.Equal("fireOneAndTwo", CommonMethodNameTransforms.CamelCase("FIREOneAndTwo"));
         Assert.Equal("fire", CommonMethodNameTransforms.CamelCase("FIRE"));
-        Assert.Throws<ArgumentNullException>(() => CommonMethodNameTransforms.CamelCase(null));
+        Assert.Throws<ArgumentNullException>(() => CommonMethodNameTransforms.CamelCase(null!));
         Assert.Equal(string.Empty, CommonMethodNameTransforms.CamelCase(string.Empty));
     }
 
@@ -25,7 +25,7 @@ public void Prefix()
         Assert.Equal("Foo.Do", CommonMethodNameTransforms.Prepend("Foo.")("Do"));
         Assert.Equal("Foo.Bar/Do", CommonMethodNameTransforms.Prepend("Foo.Bar/")("Do"));
         Assert.Equal("Foo.Bar.Do", CommonMethodNameTransforms.Prepend("Foo.Bar.")("Do"));
-        Assert.Throws<ArgumentNullException>(() => CommonMethodNameTransforms.Prepend(null));
+        Assert.Throws<ArgumentNullException>(() => CommonMethodNameTransforms.Prepend(null!));
         Assert.Equal("Do", CommonMethodNameTransforms.Prepend(string.Empty)("Do"));
     }
 }

src/StreamJsonRpc.Tests/DirectMessageHandler.cs

@@ -31,7 +31,7 @@ public DirectMessageHandler()
 
     internal AsyncQueue<JToken> WrittenMessages { get; } = new AsyncQueue<JToken>();
 
-    protected override async ValueTask<JsonRpcMessage> ReadCoreAsync(CancellationToken cancellationToken)
+    protected override async ValueTask<JsonRpcMessage?> ReadCoreAsync(CancellationToken cancellationToken)
     {
         return this.Formatter.Deserialize(await this.MessagesToRead.DequeueAsync(cancellationToken));
     }

src/StreamJsonRpc.Tests/DuplexPipeMarshalingTests.cs

@@ -28,7 +28,9 @@ public class DuplexPipeMarshalingTests : TestBase, IAsyncLifetime
     private JsonRpc clientRpc;
     private MultiplexingStream clientMx;
 
+#pragma warning disable CS8618 // Non-nullable field is uninitialized. Consider declaring as nullable.
     public DuplexPipeMarshalingTests(ITestOutputHelper logger)
+#pragma warning restore CS8618 // Non-nullable field is uninitialized. Consider declaring as nullable.
         : base(logger)
     {
     }
@@ -375,7 +377,7 @@ public async Task PipeRemainsOpenAfterSuccessfulServerResult()
         (IDuplexPipe, IDuplexPipe) pipePair = FullDuplexStream.CreatePipePair();
         await this.clientRpc.InvokeWithCancellationAsync(nameof(Server.AcceptPipeAndChatLater), new object[] { false, pipePair.Item2 }, this.TimeoutToken);
 
-        await WhenAllSucceedOrAnyFault(TwoWayTalkAsync(pipePair.Item1, writeOnOdd: true, this.TimeoutToken), this.server.ChatLaterTask);
+        await WhenAllSucceedOrAnyFault(TwoWayTalkAsync(pipePair.Item1, writeOnOdd: true, this.TimeoutToken), this.server.ChatLaterTask!);
         pipePair.Item1.Output.Complete();
 
         // Verify that the pipe closes when the server completes writing.
@@ -432,7 +434,7 @@ public async Task ClientSendsMultiplePipes()
     [Fact]
     public async Task ClientSendsNullPipe()
     {
-        await this.clientRpc.InvokeWithCancellationAsync(nameof(Server.AcceptNullPipe), new object[] { null }, this.TimeoutToken);
+        await this.clientRpc.InvokeWithCancellationAsync(nameof(Server.AcceptNullPipe), new object?[] { null }, this.TimeoutToken);
     }
 
     /// <summary>
@@ -471,7 +473,7 @@ public async Task InvokeWithPipe_ServerMethodDoesNotExist_ChannelOfferCanceled()
         // It may or may not have already occurred so for test stability, we code our assertion to handle both cases.
         try
         {
-            MultiplexingStream.Channel serverChannel = this.serverMx.AcceptChannel(channelIdOffered.Value);
+            MultiplexingStream.Channel serverChannel = this.serverMx.AcceptChannel(channelIdOffered!.Value);
 
             // The client had not yet canceled the offer. So wait for the client to close the channel now that we've accepted it.
             await serverChannel.Completion.WithCancellation(this.TimeoutToken);
@@ -575,7 +577,7 @@ public async Task OverloadedMethod(bool writeOnOdd, IDuplexPipe pipe, string mes
 
     private class Server
     {
-        internal Task ChatLaterTask { get; private set; }
+        internal Task? ChatLaterTask { get; private set; }
 
         public async Task<long> AcceptReadablePipe(string fileName, IDuplexPipe content, CancellationToken cancellationToken)
         {
@@ -702,7 +704,7 @@ public Task AcceptPipeAndChatLater(bool writeOnOdd, IDuplexPipe pipe, Cancellati
 
     private class ServerWithIDuplexPipeReturningMethod
     {
-        public IDuplexPipe MethodThatReturnsIDuplexPipe() => null;
+        public IDuplexPipe? MethodThatReturnsIDuplexPipe() => null;
     }
 
     private class OneWayStreamWrapper : Stream

src/StreamJsonRpc.Tests/FullDuplexStream.cs

@@ -20,8 +20,6 @@ public class FullDuplexStream : Stream
         /// The options to use when creating the value for <see cref="enqueuedSource"/>.
         /// </summary>
         private const TaskCreationOptions EnqueuedSourceOptions = TaskCreationOptions.RunContinuationsAsynchronously;
-        private static readonly byte[] EmptyByteArray = new byte[0];
-        private static readonly Task CompletedTask = Task.FromResult<object>(null);
 
         /// <summary>
         /// The messages posted by the <see cref="other"/> party,
@@ -32,13 +30,15 @@ public class FullDuplexStream : Stream
         /// <summary>
         /// The stream to write to.
         /// </summary>
+#pragma warning disable CS8618 // Non-nullable field is uninitialized. Consider declaring as nullable.
         private FullDuplexStream other;
+#pragma warning restore CS8618 // Non-nullable field is uninitialized. Consider declaring as nullable.
 
         /// <summary>
         /// The completion source for a Task that completes whenever a message
         /// is enqueued to <see cref="readQueue"/>.
         /// </summary>
-        private TaskCompletionSource<object> enqueuedSource = new TaskCompletionSource<object>(EnqueuedSourceOptions);
+        private TaskCompletionSource<object?> enqueuedSource = new TaskCompletionSource<object?>(EnqueuedSourceOptions);
 
         /// <summary>
         /// Gets or sets a value indicating whether the stream is disposed.
@@ -71,7 +71,7 @@ public override long Position
         /// Gets or sets a delegate that is called just before writing to the stream,
         /// but after the caller's cancellation token has been checked.
         /// </summary>
-        public BeforeWriteToFullDuplexStreamDelegate BeforeWrite { get; set; }
+        public BeforeWriteToFullDuplexStreamDelegate? BeforeWrite { get; set; }
 
         /// <summary>
         /// Creates a pair of streams that can be passed to two parties
@@ -101,10 +101,10 @@ public override async Task<int> ReadAsync(byte[] buffer, int offset, int count,
             Requires.Range(offset + count <= buffer.Length, nameof(count));
 
             cancellationToken.ThrowIfCancellationRequested();
-            Message message = null;
+            Message? message = null;
             while (message == null)
             {
-                Task waitTask = null;
+                Task? waitTask = null;
                 lock (this.readQueue)
                 {
                     if (this.readQueue.Count > 0)
@@ -123,7 +123,7 @@ public override async Task<int> ReadAsync(byte[] buffer, int offset, int count,
                     {
                         // Arrange to wake up when a new message is posted, or when the caller's CancellationToken is canceled.
                         var wakeUpEarly = new TaskCompletionSource<object>();
-                        using (cancellationToken.Register(state => ((TaskCompletionSource<object>)state).SetResult(null), wakeUpEarly, false))
+                        using (cancellationToken.Register(state => ((TaskCompletionSource<object?>)state).SetResult(null), wakeUpEarly, false))
                         {
                             await Task.WhenAny(waitTask, wakeUpEarly.Task).ConfigureAwait(false);
                         }
@@ -206,7 +206,7 @@ public override Task WriteAsync(byte[] buffer, int offset, int count, Cancellati
         {
             cancellationToken.ThrowIfCancellationRequested();
             this.Write(buffer, offset, count);
-            return CompletedTask;
+            return Task.CompletedTask;
         }
 
         /// <inheritdoc />
@@ -242,7 +242,7 @@ protected override void Dispose(bool disposing)
 
             // Sending an empty buffer is the traditional way to signal
             // that the transmitting stream has closed.
-            this.other.PostMessage(new Message(EmptyByteArray));
+            this.other.PostMessage(new Message(Array.Empty<byte>()));
             base.Dispose(disposing);
         }
 
@@ -254,12 +254,12 @@ private void PostMessage(Message message)
         {
             Requires.NotNull(message, nameof(message));
 
-            TaskCompletionSource<object> enqueuedSource;
+            TaskCompletionSource<object?> enqueuedSource;
             lock (this.readQueue)
             {
                 this.readQueue.Add(message);
                 Monitor.PulseAll(this.readQueue);
-                enqueuedSource = Interlocked.Exchange(ref this.enqueuedSource, new TaskCompletionSource<object>(EnqueuedSourceOptions));
+                enqueuedSource = Interlocked.Exchange(ref this.enqueuedSource, new TaskCompletionSource<object?>(EnqueuedSourceOptions));
             }
 
             enqueuedSource.TrySetResult(null);

src/StreamJsonRpc.Tests/HeaderDelimitedMessageHandlerTests.cs

@@ -62,8 +62,8 @@ public async Task ReadCoreAsync_HandlesSpacingCorrectly()
         this.receivingStream.Flush();
         this.receivingStream.Position = 0;
 
-        var readContent = (JsonRpcRequest)await this.handler.ReadAsync(CancellationToken.None);
-        Assert.Equal("test", readContent.Method);
+        var readContent = (JsonRpcRequest?)await this.handler.ReadAsync(CancellationToken.None);
+        Assert.Equal("test", readContent!.Method);
 
         this.receivingStream.Position = 0;
         this.receivingStream.SetLength(0);
@@ -77,8 +77,8 @@ public async Task ReadCoreAsync_HandlesSpacingCorrectly()
         this.receivingStream.Flush();
         this.receivingStream.Position = 0;
 
-        readContent = (JsonRpcRequest)await this.handler.ReadAsync(CancellationToken.None);
-        Assert.Equal("test", readContent.Method);
+        readContent = (JsonRpcRequest?)await this.handler.ReadAsync(CancellationToken.None);
+        Assert.Equal("test", readContent!.Method);
     }
 
     [Fact]
@@ -95,8 +95,8 @@ public async Task ReadCoreAsync_HandlesUtf8CharsetCorrectly()
         this.receivingStream.Flush();
         this.receivingStream.Position = 0;
 
-        var readContent = (JsonRpcRequest)await this.handler.ReadAsync(CancellationToken.None);
-        Assert.Equal("test", readContent.Method);
+        var readContent = (JsonRpcRequest?)await this.handler.ReadAsync(CancellationToken.None);
+        Assert.Equal("test", readContent!.Method);
 
         this.receivingStream.Position = 0;
         this.receivingStream.SetLength(0);
@@ -112,8 +112,8 @@ public async Task ReadCoreAsync_HandlesUtf8CharsetCorrectly()
         this.receivingStream.Flush();
         this.receivingStream.Position = 0;
 
-        readContent = (JsonRpcRequest)await this.handler.ReadAsync(CancellationToken.None);
-        Assert.Equal("test", readContent.Method);
+        readContent = (JsonRpcRequest?)await this.handler.ReadAsync(CancellationToken.None);
+        Assert.Equal("test", readContent!.Method);
     }
 
     [Fact]

src/StreamJsonRpc.Tests/InteropTestBase.cs

@@ -18,7 +18,6 @@
 public class InteropTestBase : TestBase
 {
     protected readonly DirectMessageHandler messageHandler;
-    protected readonly JsonRpc rpc;
 
     public InteropTestBase(ITestOutputHelper logger, bool serverTest)
         : base(logger)

src/StreamJsonRpc.Tests/JsonMessageFormatterTests.cs

@@ -50,7 +50,7 @@ public void ProtocolVersion_AcceptedVersions(int major, int minor)
     public void ProtocolVersion_RejectsOtherVersions()
     {
         var formatter = new JsonMessageFormatter();
-        Assert.Throws<ArgumentNullException>(() => formatter.ProtocolVersion = null);
+        Assert.Throws<ArgumentNullException>(() => formatter.ProtocolVersion = null!);
         Assert.Throws<NotSupportedException>(() => formatter.ProtocolVersion = new Version(0, 0));
         Assert.Throws<NotSupportedException>(() => formatter.ProtocolVersion = new Version(1, 1));
         Assert.Throws<NotSupportedException>(() => formatter.ProtocolVersion = new Version(2, 1));
@@ -108,7 +108,7 @@ public void JTokenParserHonorsSettingsOnSerializer()
         string jsonRequest = @"{""jsonrpc"":""2.0"",""method"":""asdf"",""params"":[""2019-01-29T03:37:28.4433841Z""]}";
         ReadOnlySequence<byte> jsonSequence = new ReadOnlySequence<byte>(formatter.Encoding.GetBytes(jsonRequest));
         var jsonMessage = (JsonRpcRequest)formatter.Deserialize(jsonSequence);
-        Assert.True(jsonMessage.TryGetArgumentByNameOrIndex(null, 0, typeof(string), out object value));
+        Assert.True(jsonMessage.TryGetArgumentByNameOrIndex(null, 0, typeof(string), out object? value));
         Assert.IsType<string>(value);
         Assert.Equal("2019-01-29T03:37:28.4433841Z", value);
     }

src/StreamJsonRpc.Tests/JsonRpcClient10InteropTests.cs

@@ -42,7 +42,7 @@ public async Task ClientRecognizesResultWithNullError()
         {
             id = request["id"],
             result = expectedResult,
-            error = (object)null, // JSON-RPC 1.0 requires that the error property be specified as null in successful responses.
+            error = (object?)null, // JSON-RPC 1.0 requires that the error property be specified as null in successful responses.
         });
         string actualResult = await invokeTask;
         Assert.Equal(expectedResult, actualResult);
@@ -57,7 +57,7 @@ public async Task ClientRecognizesErrorWithNullResult()
         this.Send(new
         {
             id = request.id,
-            result = (object)null, // JSON-RPC 1.0 requires that result be specified and null if there is an error.
+            result = (object?)null, // JSON-RPC 1.0 requires that result be specified and null if there is an error.
             error = new { message = expectedErrorMessage },
         });
         var error = await Assert.ThrowsAsync<RemoteInvocationException>(() => invokeTask);

src/StreamJsonRpc.Tests/JsonRpcClient20InteropTests.cs

@@ -301,7 +301,7 @@ public async Task ErrorResponseIncludesCallstack()
         };
         this.Send(errorObject);
         var ex = await Assert.ThrowsAsync<RemoteInvocationException>(() => requestTask);
-        var commonErrorData = ((JToken)ex.ErrorData).ToObject<CommonErrorData>();
+        var commonErrorData = ((JToken)ex.ErrorData!).ToObject<CommonErrorData>();
         Assert.Equal(errorObject.error.data.stack, commonErrorData.StackTrace);
     }
 
@@ -327,7 +327,7 @@ public async Task ErrorResponseIncludesCallstackAndNumericErrorCode()
         };
         this.Send(errorObject);
         var ex = await Assert.ThrowsAsync<RemoteInvocationException>(() => requestTask);
-        var commonErrorData = ((JToken)ex.ErrorData).ToObject<CommonErrorData>();
+        var commonErrorData = ((JToken?)ex.ErrorData)!.ToObject<CommonErrorData>();
         Assert.Equal(errorObject.error.data.stack, commonErrorData.StackTrace);
         Assert.Equal(-2147467261, commonErrorData.HResult);
     }
@@ -355,7 +355,7 @@ public async Task ErrorResponseUsesUnexpectedDataTypes()
         };
         this.Send(errorObject);
         var ex = await Assert.ThrowsAsync<RemoteInvocationException>(() => requestTask);
-        JToken errorDataToken = (JToken)ex.ErrorData;
+        JToken errorDataToken = (JToken)ex.ErrorData!;
         Assert.Throws<JsonReaderException>(() => errorDataToken.ToObject<CommonErrorData>());
         Assert.Equal(errorData.stack.foo, errorDataToken["stack"].Value<int>("foo"));
     }
@@ -406,7 +406,7 @@ public async Task ErrorResponseDataFieldIsPrimitive()
         });
         var ex = await Assert.ThrowsAsync<RemoteInvocationException>(() => requestTask);
         Assert.Equal(expectedMessage, ex.Message);
-        Assert.Equal(expectedData, ((JToken)ex.ErrorData)?.Value<string>());
+        Assert.Equal(expectedData, ((JToken?)ex.ErrorData)?.Value<string>());
     }
 
     [Fact]

src/StreamJsonRpc.Tests/JsonRpcCustomRequestIdTests.cs

@@ -60,7 +60,7 @@ public JsonRpcWithStringIds(IJsonRpcMessageHandler handler)
 
         protected override RequestId CreateNewRequestId()
         {
-            return new RequestId("prefix-" + base.CreateNewRequestId().Number.Value.ToString());
+            return new RequestId("prefix-" + base.CreateNewRequestId().Number);
         }
     }
 }

src/StreamJsonRpc.Tests/JsonRpcJsonHeadersTests.cs

@@ -175,8 +175,8 @@ public async Task ExceptionControllingErrorData()
 
         // C# dynamic is infamously unstable. If this test ends up being unstable, yet the dump clearly shows the fields are there even though the exception claims it isn't,
         // that's consistent with the instability I've seen before. Switching to using JToken APIs will fix the instability, but it relies on using the JsonMessageFormatter.
-        dynamic data = exception.ErrorData;
-        dynamic myCustomData = data.myCustomData;
+        dynamic? data = exception.ErrorData;
+        dynamic myCustomData = data!.myCustomData;
         string actual = myCustomData;
         Assert.Equal("hi", actual);
     }
@@ -189,7 +189,7 @@ public async Task CanPassExceptionFromServer()
 #pragma warning restore SA1139 // Use literal suffix notation instead of casting
         RemoteInvocationException exception = await Assert.ThrowsAnyAsync<RemoteInvocationException>(() => this.clientRpc.InvokeAsync(nameof(Server.MethodThatThrowsUnauthorizedAccessException)));
         Assert.Equal((int)JsonRpcErrorCode.InvocationError, exception.ErrorCode);
-        var errorData = ((JToken)exception.ErrorData).ToObject<CommonErrorData>();
+        var errorData = ((JToken?)exception.ErrorData)!.ToObject<CommonErrorData>();
         Assert.NotNull(errorData.StackTrace);
         Assert.StrictEqual(COR_E_UNAUTHORIZEDACCESS, errorData.HResult);
     }
@@ -207,7 +207,7 @@ protected override void InitializeFormattersAndHandlers()
     public class ParamsObjectWithCustomNames
     {
         [DataMember(Name = "argument")]
-        public string TheArgument { get; set; }
+        public string? TheArgument { get; set; }
     }
 
     private class StringBase64Converter : JsonConverter