fix: override base class indexer to set OpenApiAny values

Author: MaggieKimani1

src/Microsoft.OpenApi/Any/OpenApiExtensionDictionary.cs

@@ -0,0 +1,65 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license.
+
+using System;
+using System.Collections.Generic;
+using System.Text.Json.Nodes;
+using Microsoft.OpenApi.Interfaces;
+
+namespace Microsoft.OpenApi.Any
+{
+    /// <summary>
+    /// A dictionary of OpenApi extensions.
+    /// </summary>
+    public class OpenApiExtensionDictionary : Dictionary<string, IOpenApiExtension>
+    {
+        /// <summary>
+        /// Override the base class indexer to return OpenApiAny.
+        /// </summary>
+        /// <param name="key"></param>
+        /// <returns></returns>
+        public new OpenApiAny this[string key]
+        {           
+            get => (OpenApiAny)base[key];
+            set => base[key] = ConvertIfJsonNode(value);
+        }
+
+        /// <summary>
+        /// Adds an extension to the dictionary.
+        /// </summary>
+        /// <param name="key"></param>
+        /// <param name="value"></param>
+        public void Add(string key, object value)
+        {
+            base.Add(key, ConvertIfJsonNode(value));
+        }
+
+        private static IOpenApiExtension ConvertIfJsonNode(object? value)
+        {
+            return value switch
+            {
+                IOpenApiExtension extension => extension,
+                JsonNode node => (OpenApiAny)node,
+                _ => throw new InvalidOperationException($"Cannot convert value of type '{value?.GetType().Name}' to IOpenApiExtension.")
+            };
+        }
+
+        /// <summary>
+        /// Test the OpenApiExtensionDictionary and base class implementations.
+        /// </summary>
+        public static void TestExtensions()
+        {
+            var jsonNode = new JsonObject();
+            var extensions = new OpenApiExtensionDictionary
+            {
+                ["x-key"] = jsonNode
+            };
+            extensions.Add("x-key", jsonNode);
+            var extensions2 = new Dictionary<string, IOpenApiExtension>
+            {
+                ["x-key"] = (OpenApiAny)jsonNode
+            };
+            extensions2.Add("x-key", (OpenApiAny)jsonNode);
+        }
+    }
+}

src/Microsoft.OpenApi/Interfaces/IOpenApiExtensible.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license.
 
 using System.Collections.Generic;
+using Microsoft.OpenApi.Any;
 
 namespace Microsoft.OpenApi.Interfaces
 {
@@ -13,6 +14,6 @@ public interface IOpenApiExtensible : IOpenApiElement
         /// <summary>
         /// Specification extensions.
         /// </summary>
-        Dictionary<string, IOpenApiExtension>? Extensions { get; set; }
+        OpenApiExtensionDictionary? Extensions { get; set; }
     }
 }

src/Microsoft.OpenApi/Models/OpenApiCallback.cs

@@ -3,6 +3,8 @@
 
 using System;
 using System.Collections.Generic;
+using System.Text.Json.Nodes;
+using Microsoft.OpenApi.Any;
 using Microsoft.OpenApi.Expressions;
 using Microsoft.OpenApi.Interfaces;
 using Microsoft.OpenApi.Models.Interfaces;
@@ -22,7 +24,7 @@ public class OpenApiCallback : IOpenApiExtensible, IOpenApiCallback
         /// <summary>
         /// This object MAY be extended with Specification Extensions.
         /// </summary>
-        public Dictionary<string, IOpenApiExtension>? Extensions { get; set; }
+        public OpenApiExtensionDictionary? Extensions { get; set; }
 
         /// <summary>
         /// Parameter-less constructor
@@ -90,6 +92,7 @@ internal void SerializeInternal(IOpenApiWriter writer, OpenApiSpecVersion versio
 
             // extensions
             writer.WriteExtensions(Extensions, version);
+            Extensions!["x-extensions"] = new JsonObject(); //this works
 
             writer.WriteEndObject();
         }