Compare updated template evaluator (#4092)

src/Sdk/WorkflowParser/IStepJsonConverter.cs

@@ -0,0 +1,70 @@
+#nullable disable // Consider removing in the future to minimize likelihood of NullReferenceException; refer https://learn.microsoft.com/en-us/dotnet/csharp/nullable-references
+
+using System;
+using System.Reflection;
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
+namespace GitHub.Actions.WorkflowParser
+{
+    internal sealed class IStepJsonConverter : JsonConverter
+    {
+        public override Boolean CanWrite
+        {
+            get
+            {
+                return false;
+            }
+        }
+
+        public override Boolean CanConvert(Type objectType)
+        {
+            return typeof(IStep).GetTypeInfo().IsAssignableFrom(objectType.GetTypeInfo());
+        }
+
+        public override Object ReadJson(
+            JsonReader reader,
+            Type objectType,
+            Object existingValue,
+            JsonSerializer serializer)
+        {
+            if (reader.TokenType != JsonToken.StartObject)
+            {
+                return null;
+            }
+
+            JObject value = JObject.Load(reader);
+            Object newValue = null;
+
+            if (value.TryGetValue("Uses", StringComparison.OrdinalIgnoreCase, out _))
+            {
+                newValue = new ActionStep();
+            }
+            else if (value.TryGetValue("Run", StringComparison.OrdinalIgnoreCase, out _))
+            {
+                newValue = new RunStep();
+            }
+            else
+            {
+                return existingValue;
+            }
+
+
+            if (value != null)
+            {
+                using JsonReader objectReader = value.CreateReader();
+                serializer.Populate(objectReader, newValue);
+            }
+
+            return newValue;
+        }
+
+        public override void WriteJson(
+            JsonWriter writer,
+            Object value,
+            JsonSerializer serializer)
+        {
+            throw new NotImplementedException();
+        }
+    }
+}