Remove a few more instances of newtonsoft

src/Features/LanguageServer/Protocol/Handler/CodeActions/CodeActionResolveData.cs

@@ -3,7 +3,7 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Collections.Immutable;
-using Newtonsoft.Json;
+using System.Text.Json.Serialization;
 using LSP = Roslyn.LanguageServer.Protocol;
 
 namespace Microsoft.CodeAnalysis.LanguageServer.Handler.CodeActions
@@ -33,10 +33,10 @@ internal class CodeActionResolveData
 
         public string[] CodeActionPath { get; }
 
-        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
+        [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
         public string[]? FixAllFlavors { get; }
 
-        [JsonProperty(NullValueHandling = NullValueHandling.Ignore)]
+        [JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)]
         public ImmutableArray<LSP.CodeAction>? NestedCodeActions { get; }
 
         public CodeActionResolveData(

src/Features/LanguageServer/Protocol/Handler/CodeActions/RoslynFixAllCodeAction.cs

@@ -2,15 +2,13 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System.Runtime.Serialization;
-using Newtonsoft.Json;
+using System.Text.Json.Serialization;
 using Roslyn.LanguageServer.Protocol;
 
 namespace Microsoft.CodeAnalysis.LanguageServer.Handler.CodeActions;
 
-[DataContract]
 internal sealed class RoslynFixAllCodeAction(string scope) : CodeAction
 {
-    [JsonProperty(PropertyName = "scope")]
+    [JsonPropertyName("scope")]
     public string Scope { get; } = scope;
 }

src/Features/LanguageServer/Protocol/Handler/Configuration/DidChangeConfigurationNotificationHandler_OnInitialized.cs

@@ -2,10 +2,10 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Text.Json;
 using System.Threading;
 using System.Threading.Tasks;
 using Roslyn.LanguageServer.Protocol;
-using Newtonsoft.Json.Linq;
 
 namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Configuration
 {
@@ -15,7 +15,7 @@ public async Task OnInitializedAsync(ClientCapabilities clientCapabilities, Requ
         {
             if (clientCapabilities?.Workspace?.DidChangeConfiguration?.DynamicRegistration is true)
             {
-                await _clientLanguageServerManager.SendRequestAsync<RegistrationParams, JObject>(
+                await _clientLanguageServerManager.SendRequestAsync<RegistrationParams, JsonElement>(
                     methodName: Methods.ClientRegisterCapabilityName,
                     @params: new RegistrationParams()
                     {

src/Features/LanguageServer/Protocol/Handler/Testing/RunTestsPartialResult.cs

@@ -3,12 +3,11 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Text.Json.Serialization;
-using Newtonsoft.Json;
 
 namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Testing;
 
 internal record RunTestsPartialResult(
     [property: JsonPropertyName("stage")] string Stage,
     [property: JsonPropertyName("message")] string Message,
-    [property: JsonPropertyName("progress"), JsonProperty(NullValueHandling = NullValueHandling.Ignore)] TestProgress? Progress
+    [property: JsonPropertyName("progress"), JsonIgnore(Condition = JsonIgnoreCondition.WhenWritingNull)] TestProgress? Progress
 );