Implement serialization and deserialization logic for unrecognized JSON schema keywords

Author: MaggieKimani1

src/Microsoft.OpenApi/Models/OpenApiConstants.cs

@@ -480,6 +480,11 @@ public static class OpenApiConstants
         /// </summary>
         public const string Properties = "properties";
 
+        /// <summary>
+        /// Field: UnrecognizedKeywords
+        /// </summary>
+        public const string UnrecognizedKeywords = "unrecognizedKeywords";
+
         /// <summary>
         /// Field: Pattern Properties
         /// </summary>

src/Microsoft.OpenApi/Models/OpenApiSchema.cs

@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation. All rights reserved.
+// Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license. 
 
 using System;
@@ -327,6 +327,11 @@ public virtual IList<JsonNode> Examples
         /// </summary>
         public virtual IDictionary<string, IOpenApiExtension> Extensions { get; set; } = new Dictionary<string, IOpenApiExtension>();
 
+        /// <summary>
+        /// This object stores any unrecognized keywords found in the schema.
+        /// </summary>
+        public virtual IDictionary<string, JsonNode> UnrecognizedKeywords { get; set; } = new Dictionary<string, JsonNode>();
+
         /// <summary>
         /// Indicates object is a placeholder reference to an actual object and does not contain valid data.
         /// </summary>
@@ -403,6 +408,7 @@ public OpenApiSchema(OpenApiSchema schema)
             UnresolvedReference = schema?.UnresolvedReference ?? UnresolvedReference;
             Reference = schema?.Reference != null ? new(schema?.Reference) : null;
             Annotations = schema?.Annotations != null ? new Dictionary<string, object>(schema?.Annotations) : null;
+            UnrecognizedKeywords = schema?.UnrecognizedKeywords != null ? new Dictionary<string, JsonNode>(schema?.UnrecognizedKeywords) : null;
         }
 
         /// <summary>
@@ -554,6 +560,12 @@ public void SerializeInternal(IOpenApiWriter writer, OpenApiSpecVersion version,
             // extensions
             writer.WriteExtensions(Extensions, version);
 
+            // Unrecognized keywords
+            if (UnrecognizedKeywords.Any())
+            {
+                writer.WriteOptionalMap(OpenApiConstants.UnrecognizedProperties, UnrecognizedKeywords, (w,s) => w.WriteAny(s));
+            }
+
             writer.WriteEndObject();
         }
 

src/Microsoft.OpenApi/Reader/V31/OpenApiSchemaDeserializer.cs

@@ -7,6 +7,8 @@
 using Microsoft.OpenApi.Reader.ParseNodes;
 using System.Collections.Generic;
 using System.Globalization;
+using System.Linq;
+using System.Text.Json.Nodes;
 
 namespace Microsoft.OpenApi.Reader.V31
 {
@@ -254,7 +256,17 @@ public static OpenApiSchema LoadSchema(ParseNode node, OpenApiDocument hostDocum
 
             foreach (var propertyNode in mapNode)
             {
-                propertyNode.ParseField(schema, _openApiSchemaFixedFields, _openApiSchemaPatternFields);
+                bool isRecognized = _openApiSchemaFixedFields.ContainsKey(propertyNode.Name) ||
+                        _openApiSchemaPatternFields.Any(p => p.Key(propertyNode.Name));
+
+                if (isRecognized)
+                {
+                    propertyNode.ParseField(schema, _openApiSchemaFixedFields, _openApiSchemaPatternFields);
+                }
+                else
+                {
+                    schema.UnrecognizedKeywords[propertyNode.Name] = propertyNode.JsonNode;
+                }
             }
 
             if (schema.Extensions.ContainsKey(OpenApiConstants.NullableExtension))

src/Microsoft.OpenApi/Writers/OpenApiWriterExtensions.cs

@@ -5,6 +5,7 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
+using System.Text.Json.Nodes;
 using Microsoft.OpenApi.Interfaces;
 
 namespace Microsoft.OpenApi.Writers
@@ -253,6 +254,25 @@ public static void WriteRequiredMap(
             writer.WriteMapInternal(name, elements, action);
         }
 
+        /// <summary>
+        /// Write the optional Open API element map (string to string mapping).
+        /// </summary>
+        /// <param name="writer">The Open API writer.</param>
+        /// <param name="name">The property name.</param>
+        /// <param name="elements">The map values.</param>
+        /// <param name="action">The map element writer action.</param>
+        public static void WriteOptionalMap(
+            this IOpenApiWriter writer,
+            string name,
+            IDictionary<string, JsonNode> elements,
+            Action<IOpenApiWriter, JsonNode> action)
+        {
+            if (elements != null && elements.Any())
+            {
+                writer.WriteMapInternal(name, elements, action);
+            }
+        }
+
         /// <summary>
         /// Write the optional Open API element map (string to string mapping).
         /// </summary>