Track cloned objects to avoid StackOverflowExceptions during cloning

src/Microsoft.OpenApi.Readers/Microsoft.OpenApi.Readers.csproj

@@ -10,7 +10,7 @@
         <Company>Microsoft</Company>
         <Title>Microsoft.OpenApi.Readers</Title>
         <PackageId>Microsoft.OpenApi.Readers</PackageId>
-        <Version>1.6.4-preview2</Version>
+        <Version>1.6.4-preview3</Version>
         <Description>OpenAPI.NET Readers for JSON and YAML documents</Description>
         <Copyright>© Microsoft Corporation. All rights reserved.</Copyright>
         <PackageTags>OpenAPI .NET</PackageTags>

src/Microsoft.OpenApi/Helpers/DictionaryCloneHelper.cs

@@ -9,7 +9,7 @@ namespace Microsoft.OpenApi.Helpers
     /// <summary>
     /// Helper class for deep cloning dictionaries.
     /// </summary>
-    internal class DictionaryCloneHelper
+    internal static class DictionaryCloneHelper
     {
         /// <summary>
         /// Deep clone key value pairs in a dictionary.
@@ -21,14 +21,26 @@ internal class DictionaryCloneHelper
         internal static Dictionary<T, U> Clone<T, U>(IDictionary<T, U> dictionary)
         {            
             if (dictionary is null) return null;
+
             var clonedDictionary = new Dictionary<T, U>(dictionary.Keys.Count);
+            var clonedObjects = new Dictionary<object, object>();
 
-            foreach (var kvp in dictionary)
+            foreach (var keyValuePair in dictionary)
             {
-                // Create instance of the specified type using the constructor matching the specified parameter types.
-                clonedDictionary[kvp.Key] = (U)Activator.CreateInstance(kvp.Value.GetType(), kvp.Value);
-            }
-
+                // If the object has already been cloned, use the cloned object instead of cloning it again
+                if (clonedObjects.TryGetValue(keyValuePair.Value, out var clonedValue))
+                {
+                    clonedDictionary[keyValuePair.Key] = (U)clonedValue;
+                }
+                else
+                {
+                    // Create instance of the specified type using the constructor matching the specified parameter types.
+                    clonedDictionary[keyValuePair.Key] = (U)Activator.CreateInstance(keyValuePair.Value.GetType(), keyValuePair.Value);
+
+                    // Add the cloned object to the dictionary of cloned objects
+                    clonedObjects.Add(keyValuePair.Value, clonedDictionary[keyValuePair.Key]);
+                }                
+            }            
 
             return clonedDictionary;
         }

src/Microsoft.OpenApi/Microsoft.OpenApi.csproj

@@ -11,7 +11,7 @@
         <Company>Microsoft</Company>
         <Title>Microsoft.OpenApi</Title>
         <PackageId>Microsoft.OpenApi</PackageId>
-        <Version>1.6.4-preview2</Version>
+        <Version>1.6.4-preview3</Version>
         <Description>.NET models with JSON and YAML writers for OpenAPI specification</Description>
         <Copyright>© Microsoft Corporation. All rights reserved.</Copyright>
         <PackageTags>OpenAPI .NET</PackageTags>