Use 'Source'

src/Features/LanguageServer/Protocol/Handler/Diagnostics/AbstractPullDiagnosticHandler.cs

@@ -239,9 +239,9 @@ private VSDiagnostic ConvertDiagnostic(Document document, SourceText text, Diagn
             // Razor wants to handle all span mapping themselves.  So if we are in razor, return the raw doc spans, and
             // do not map them.
             var useMappedSpan = !document.IsRazorDocument();
-            return new RoslynDiagnostic
+            return new VSDiagnostic
             {
-                Client = GetType().Name,
+                Source = GetType().Name,
                 Code = diagnosticData.Id,
                 Message = diagnosticData.Message,
                 Severity = ConvertDiagnosticSeverity(diagnosticData.Severity),

src/Features/LanguageServer/Protocol/Handler/Diagnostics/RoslynDiagnostic.cs

-// Licensed to the .NET Foundation under one or more agreements.
-// 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 Microsoft.VisualStudio.LanguageServer.Protocol;
-
-namespace Microsoft.CodeAnalysis.LanguageServer.Handler.Diagnostics
-{
-    [DataContract]
-    internal class RoslynDiagnostic : VSDiagnostic
-    {
-        [DataMember(Name = "_ms_client", IsRequired = false)]
-        public string? Client { get; set; }
-    }
-}

src/VisualStudio/Core/Def/Implementation/LanguageClient/InProcLanguageServer.cs

@@ -586,9 +586,9 @@ private LSP.Diagnostic ConvertToLspDiagnostic(DiagnosticData diagnosticData, Sou
         {
             Contract.ThrowIfNull(diagnosticData.DataLocation);
 
-            var diagnostic = new RoslynDiagnostic
+            var diagnostic = new LSP.Diagnostic
             {
-                Client = this._languageClient.GetType().Name,
+                Source = this._languageClient.GetType().Name,
                 Code = diagnosticData.Id,
                 Severity = ProtocolConversions.DiagnosticSeverityToLspDiagnositcSeverity(diagnosticData.Severity),
                 Range = GetDiagnosticRange(diagnosticData.DataLocation, text, isRazor),