Fix: Examples serialization in a response object during v2->v3 upcasting or vice versa

src/Microsoft.OpenApi.Readers/V2/OpenApiOperationDeserializer.cs

@@ -4,6 +4,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Security.Cryptography.X509Certificates;
+using System.Xml.Linq;
 using Microsoft.OpenApi.Any;
 using Microsoft.OpenApi.Extensions;
 using Microsoft.OpenApi.Models;
@@ -194,7 +195,8 @@ internal static OpenApiRequestBody CreateRequestBody(
                     k => k,
                     _ => new OpenApiMediaType
                     {
-                        Schema = bodyParameter.Schema
+                        Schema = bodyParameter.Schema,
+                        Examples = bodyParameter.Examples
                     }),
                 Extensions = bodyParameter.Extensions
             };

src/Microsoft.OpenApi.Readers/V2/OpenApiParameterDeserializer.cs

@@ -95,12 +95,17 @@ internal static partial class OpenApiV2Deserializer
                     "schema",
                     (o, n) => o.Schema = LoadSchema(n)
                 },
+                {
+                    "x-examples",
+                    LoadParameterExamplesExtension
+                },
             };
 
         private static readonly PatternFieldMap<OpenApiParameter> _parameterPatternFields =
             new()
             {
-                {s => s.StartsWith("x-"), (o, p, n) => o.AddExtension(p, LoadExtension(p, n))}
+                {s => s.StartsWith("x-") && !s.Equals(OpenApiConstants.ExamplesExtension, StringComparison.OrdinalIgnoreCase),
+                    (o, p, n) => o.AddExtension(p, LoadExtension(p, n))} 
             };
 
         private static readonly AnyFieldMap<OpenApiParameter> _parameterAnyFields =
@@ -166,6 +171,12 @@ private static void LoadStyle(OpenApiParameter p, string v)
             }
         }
 
+        private static void LoadParameterExamplesExtension(OpenApiParameter parameter, ParseNode node)
+        {
+            var examples = LoadExamplesExtension(node);
+            node.Context.SetTempStorage(TempStorageKeys.Examples, examples, parameter);
+        }
+
         private static OpenApiSchema GetOrCreateSchema(OpenApiParameter p)
         {
             if (p.Schema == null)
@@ -250,6 +261,14 @@ public static OpenApiParameter LoadParameter(ParseNode node, bool loadRequestBod
                 node.Context.SetTempStorage("schema", null);
             }
 
+            // load examples from storage and add them to the parameter
+            var examples = node.Context.GetFromTempStorage<Dictionary<string, OpenApiExample>>(TempStorageKeys.Examples, parameter);
+            if (examples != null)
+            {
+                parameter.Examples = examples;
+                node.Context.SetTempStorage("examples", null);
+            }
+
             var isBodyOrFormData = (bool)node.Context.GetFromTempStorage<object>(TempStorageKeys.ParameterIsBodyOrFormData);
             if (isBodyOrFormData && !loadRequestBody)
             {

src/Microsoft.OpenApi.Readers/V2/OpenApiResponseDeserializer.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
 
+using System;
 using System.Collections.Generic;
 using Microsoft.OpenApi.Extensions;
 using Microsoft.OpenApi.Models;
@@ -28,6 +29,10 @@ internal static partial class OpenApiV2Deserializer
                 "examples",
                 LoadExamples
             },
+            {
+                "x-examples",
+                LoadResponseExamplesExtension
+            },
             {
                 "schema",
                 (o, n) => n.Context.SetTempStorage(TempStorageKeys.ResponseSchema, LoadSchema(n), o)
@@ -37,7 +42,8 @@ internal static partial class OpenApiV2Deserializer
         private static readonly PatternFieldMap<OpenApiResponse> _responsePatternFields =
             new()
             {
-                {s => s.StartsWith("x-"), (o, p, n) => o.AddExtension(p, LoadExtension(p, n))}
+                {s => s.StartsWith("x-") && !s.Equals(OpenApiConstants.ExamplesExtension, StringComparison.OrdinalIgnoreCase), 
+                    (o, p, n) => o.AddExtension(p, LoadExtension(p, n))}
             };
 
         private static readonly AnyFieldMap<OpenApiMediaType> _mediaTypeAnyFields =
@@ -69,6 +75,8 @@ private static void ProcessProduces(MapNode mapNode, OpenApiResponse response, P
                 ?? context.DefaultContentType ?? new List<string> { "application/octet-stream" };
 
             var schema = context.GetFromTempStorage<OpenApiSchema>(TempStorageKeys.ResponseSchema, response);
+            var examples = context.GetFromTempStorage<Dictionary<string, OpenApiExample>>(TempStorageKeys.Examples, response)
+                ?? new Dictionary<string, OpenApiExample>();
 
             foreach (var produce in produces)
             {
@@ -84,20 +92,64 @@ private static void ProcessProduces(MapNode mapNode, OpenApiResponse response, P
                 {
                     var mediaType = new OpenApiMediaType
                     {
-                        Schema = schema
+                        Schema = schema,
+                        Examples = examples
                     };
 
                     response.Content.Add(produce, mediaType);
                 }
             }
 
             context.SetTempStorage(TempStorageKeys.ResponseSchema, null, response);
+            context.SetTempStorage(TempStorageKeys.Examples, null, response);
             context.SetTempStorage(TempStorageKeys.ResponseProducesSet, true, response);
         }
 
+        private static void LoadResponseExamplesExtension(OpenApiResponse response, ParseNode node)
+        {
+            var examples = LoadExamplesExtension(node);
+            node.Context.SetTempStorage(TempStorageKeys.Examples, examples, response);
+        }
+
+        private static Dictionary<string, OpenApiExample> LoadExamplesExtension(ParseNode node)
+        {
+            var mapNode = node.CheckMapNode(OpenApiConstants.ExamplesExtension);
+            var examples = new Dictionary<string, OpenApiExample>();
+
+            foreach (var examplesNode in mapNode)
+            {
+                // Load the media type node as an OpenApiExample object
+                var example = new OpenApiExample();
+                var exampleNode = examplesNode.Value.CheckMapNode(examplesNode.Name);
+                foreach (var valueNode in exampleNode)
+                {
+                    switch (valueNode.Name.ToLowerInvariant())
+                    {
+                        case "summary":
+                            example.Summary = valueNode.Value.GetScalarValue();
+                            break;
+                        case "description":
+                            example.Description = valueNode.Value.GetScalarValue();
+                            break;
+                        case "value":
+                            example.Value = OpenApiAnyConverter.GetSpecificOpenApiAny(valueNode.Value.CreateAny());
+                            break;
+                        case "externalValue":
+                            example.ExternalValue = valueNode.Value.GetScalarValue();
+                            break;
+                    }
+                }
+
+                examples.Add(examplesNode.Name, example);
+            }
+
+            return examples;
+        }
+
         private static void LoadExamples(OpenApiResponse response, ParseNode node)
         {
             var mapNode = node.CheckMapNode("examples");
+
             foreach (var mediaTypeNode in mapNode)
             {
                 LoadExample(response, mediaTypeNode.Name, mediaTypeNode.Value);
@@ -108,10 +160,7 @@ private static void LoadExample(OpenApiResponse response, string mediaType, Pars
         {
             var exampleNode = node.CreateAny();
 
-            if (response.Content == null)
-            {
-                response.Content = new Dictionary<string, OpenApiMediaType>();
-            }
+            response.Content ??= new Dictionary<string, OpenApiMediaType>();
 
             OpenApiMediaType mediaTypeObject;
             if (response.Content.TryGetValue(mediaType, out var value))
@@ -141,6 +190,7 @@ public static OpenApiResponse LoadResponse(ParseNode node)
             }
 
             var response = new OpenApiResponse();
+
             foreach (var property in mapNode)
             {
                 property.ParseField(response, _responseFixedFields, _responsePatternFields);

src/Microsoft.OpenApi.Readers/V2/TempStorageKeys.cs

@@ -17,5 +17,6 @@ internal static class TempStorageKeys
         public const string GlobalConsumes = "globalConsumes";
         public const string GlobalProduces = "globalProduces";
         public const string ParameterIsBodyOrFormData = "parameterIsBodyOrFormData";
+        public const string Examples = "examples";
     }
 }

src/Microsoft.OpenApi/Models/OpenApiConstants.cs

@@ -565,6 +565,11 @@ public static class OpenApiConstants
         /// </summary>
         public const string BodyName = "x-bodyName";
 
+        /// <summary>
+        /// Field: Examples Extension
+        /// </summary>
+        public const string ExamplesExtension = "x-examples";
+
         /// <summary>
         /// Field: version3_0_0
         /// </summary>

src/Microsoft.OpenApi/Models/OpenApiDocument.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;

src/Microsoft.OpenApi/Models/OpenApiExample.cs

@@ -118,6 +118,16 @@ public OpenApiExample GetEffective(OpenApiDocument doc)
         /// Serialize to OpenAPI V3 document without using reference.
         /// </summary>
         public void SerializeAsV3WithoutReference(IOpenApiWriter writer)
+        {
+            Serialize(writer, OpenApiSpecVersion.OpenApi3_0);
+        }
+
+        /// <summary>
+        /// Writes out existing examples in a mediatype object
+        /// </summary>
+        /// <param name="writer"></param>
+        /// <param name="version"></param>
+        public void Serialize(IOpenApiWriter writer, OpenApiSpecVersion version)
         {
             writer.WriteStartObject();
 
@@ -134,7 +144,7 @@ public void SerializeAsV3WithoutReference(IOpenApiWriter writer)
             writer.WriteProperty(OpenApiConstants.ExternalValue, ExternalValue);
 
             // extensions
-            writer.WriteExtensions(Extensions, OpenApiSpecVersion.OpenApi3_0);
+            writer.WriteExtensions(Extensions, version);
 
             writer.WriteEndObject();
         }

src/Microsoft.OpenApi/Models/OpenApiParameter.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using Microsoft.OpenApi.Any;
 using Microsoft.OpenApi.Extensions;
 using Microsoft.OpenApi.Interfaces;
@@ -204,14 +205,7 @@ public void SerializeAsV3(IOpenApiWriter writer)
         /// <returns>OpenApiParameter</returns>
         public OpenApiParameter GetEffective(OpenApiDocument doc)
         {
-            if (this.Reference != null)
-            {
-                return doc.ResolveReferenceTo<OpenApiParameter>(this.Reference);
-            }
-            else
-            {
-                return this;
-            }
+            return Reference != null ? doc.ResolveReferenceTo<OpenApiParameter>(Reference) : this;
         }
 
         /// <summary>
@@ -394,6 +388,20 @@ public void SerializeAsV2WithoutReference(IOpenApiWriter writer)
                 }
             }
 
+            //examples
+            if (Examples != null && Examples.Any())
+            {
+                writer.WritePropertyName(OpenApiConstants.ExamplesExtension);
+                writer.WriteStartObject();
+
+                foreach (var example in Examples)
+                {
+                    writer.WritePropertyName(example.Key);
+                    example.Value.Serialize(writer, OpenApiSpecVersion.OpenApi2_0);
+                }
+                writer.WriteEndObject();
+            }
+
             // extensions
             writer.WriteExtensions(extensionsClone, OpenApiSpecVersion.OpenApi2_0);
 

src/Microsoft.OpenApi/Models/OpenApiRequestBody.cs

@@ -96,14 +96,7 @@ public void SerializeAsV3(IOpenApiWriter writer)
         /// <returns>OpenApiRequestBody</returns>
         public OpenApiRequestBody GetEffective(OpenApiDocument doc)
         {
-            if (this.Reference != null)
-            {
-                return doc.ResolveReferenceTo<OpenApiRequestBody>(this.Reference);
-            }
-            else
-            {
-                return this;
-            }
+            return Reference != null ? doc.ResolveReferenceTo<OpenApiRequestBody>(Reference) : this;
         }
 
         /// <summary>
@@ -153,6 +146,7 @@ internal OpenApiBodyParameter ConvertToBodyParameter()
                 // To allow round-tripping we use an extension to hold the name
                 Name = "body",
                 Schema = Content.Values.FirstOrDefault()?.Schema ?? new OpenApiSchema(),
+                Examples = Content.Values.FirstOrDefault()?.Examples,
                 Required = Required,
                 Extensions = Extensions.ToDictionary(static k => k.Key, static v => v.Value)  // Clone extensions so we can remove the x-bodyName extensions from the output V2 model.
             };
@@ -184,7 +178,8 @@ internal IEnumerable<OpenApiFormDataParameter> ConvertToFormDataParameters()
                     Description = property.Value.Description,
                     Name = property.Key,
                     Schema = property.Value,
-                    Required = Content.First().Value.Schema.Required.Contains(property.Key)
+                    Examples = Content.Values.FirstOrDefault()?.Examples,
+                    Required = Content.First().Value.Schema.Required?.Contains(property.Key) ?? false
                 };
             }
         }

src/Microsoft.OpenApi/Models/OpenApiResponse.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.Collections.Generic;
@@ -101,14 +101,7 @@ public void SerializeAsV3(IOpenApiWriter writer)
         /// <returns>OpenApiResponse</returns>
         public OpenApiResponse GetEffective(OpenApiDocument doc)
         {
-            if (this.Reference != null)
-            {
-                return doc.ResolveReferenceTo<OpenApiResponse>(this.Reference);
-            }
-            else
-            {
-                return this;
-            }
+            return Reference != null ? doc.ResolveReferenceTo<OpenApiResponse>(Reference) : this;
         }
 
         /// <summary>
@@ -201,6 +194,22 @@ public void SerializeAsV2WithoutReference(IOpenApiWriter writer)
                         writer.WriteEndObject();
                     }
 
+                    if (Content.Values.Any(m => m.Examples != null && m.Examples.Any()))
+                    {
+                        writer.WritePropertyName(OpenApiConstants.ExamplesExtension);
+                        writer.WriteStartObject();
+
+                        foreach (var example in Content
+                            .Where(mediaTypePair => mediaTypePair.Value.Examples != null && mediaTypePair.Value.Examples.Any())
+                            .SelectMany(mediaTypePair => mediaTypePair.Value.Examples))
+                        {
+                            writer.WritePropertyName(example.Key);
+                            example.Value.Serialize(writer, OpenApiSpecVersion.OpenApi2_0);
+                        }
+
+                        writer.WriteEndObject();
+                    }
+
                     writer.WriteExtensions(mediatype.Value.Extensions, OpenApiSpecVersion.OpenApi2_0);
 
                     foreach (var key in mediatype.Value.Extensions.Keys)

test/Microsoft.OpenApi.Readers.Tests/Microsoft.OpenApi.Readers.Tests.csproj

@@ -28,6 +28,7 @@
     <ItemGroup>
         <ProjectReference Include="..\..\src\Microsoft.OpenApi\Microsoft.OpenApi.csproj" />
         <ProjectReference Include="..\..\src\Microsoft.OpenApi.Readers\Microsoft.OpenApi.Readers.csproj" />
+        <ProjectReference Include="..\Microsoft.OpenApi.Tests\Microsoft.OpenApi.Tests.csproj" />
     </ItemGroup>
 
 </Project>