Fixed formatting (#3559)

THIRD-PARTY-NOTICES.txt

@@ -0,0 +1,34 @@
+VSTest uses third-party libraries or other resources that may be
+distributed under licenses different than the VSTest software.
+
+In the event that we accidentally failed to list a required notice, please
+bring it to our attention by posting an issue.
+
+The attached notices are provided for information only.
+
+License notice for SimpleJSON
+-------------------------------------
+https://github.com/Bunny83/SimpleJSON
+
+The MIT License (MIT)
+
+Copyright (c) 2012-2017 Markus Göbel (Bunny83)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+

src/Microsoft.TestPlatform.Common/ExtensionFramework/Utilities/TestExtensions.cs

@@ -5,13 +5,14 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Reflection;
-using System.Text;
 
 using Microsoft.VisualStudio.TestPlatform.Common.DataCollector;
 using Microsoft.VisualStudio.TestPlatform.Common.Telemetry;
 using Microsoft.VisualStudio.TestPlatform.ObjectModel;
 using Microsoft.VisualStudio.TestPlatform.PlatformAbstractions;
 
+using SimpleJSON;
+
 #nullable disable
 
 namespace Microsoft.VisualStudio.TestPlatform.Common.ExtensionFramework.Utilities;
@@ -123,7 +124,8 @@ internal static Dictionary<string, HashSet<string>> CreateMergedDictionary(
         }
 
         // Copy all the keys in the first dictionary into the resulting dictionary.
-        var result = new Dictionary<string, HashSet<string>>(first);
+        var result = first.Where(kvp => (kvp.Value != null && kvp.Value.Count > 0))
+            .ToDictionary(kvp => kvp.Key, kvp => kvp.Value);
 
         foreach (var kvp in second)
         {
@@ -501,17 +503,22 @@ private void AddCachedExtensionToDictionary<T>(
 
     private static string SerializeExtensionDictionary(IDictionary<string, HashSet<string>> extensions)
     {
-        StringBuilder sb = new();
-
+        var jsonObject = new JSONObject();
         foreach (var kvp in extensions)
         {
             if (kvp.Value?.Count > 0)
             {
-                sb.AppendFormat("{0}=[{1}];", kvp.Key, string.Join(",", kvp.Value));
+                var jsonArray = new JSONArray();
+                foreach (var extension in kvp.Value)
+                {
+                    jsonArray.Add(new JSONString(extension));
+                }
+
+                jsonObject.Add(kvp.Key, jsonArray);
             }
         }
 
-        return sb.ToString();
+        return jsonObject.ToString();
     }
 
     private static HashSet<string> MergeSets(HashSet<string> firstSet, HashSet<string> secondSet)