Add JSON Schema 2020-12 metadata annotations to OpenApiSchemaReference

src/Microsoft.OpenApi/Interfaces/IOpenApiReferenceHolder.cs

@@ -7,23 +7,35 @@
     /// A generic interface for OpenApiReferenceable objects that have a target.
     /// </summary>
     /// <typeparam name="T">The type of the target being referenced</typeparam>
-    /// <typeparam name="V">The type of the interface implemented by both the target and the reference type</typeparam>
-    public interface IOpenApiReferenceHolder<out T, V> : IOpenApiReferenceHolder where T : IOpenApiReferenceable, V
+    /// <typeparam name="U">The type of the interface implemented by both the target and the reference type</typeparam>
+    /// <typeparam name="V">The type for the reference holding the additional fields and annotations</typeparam>
+    public interface IOpenApiReferenceHolder<out T, U, V> : IOpenApiReferenceHolder<V> where T : IOpenApiReferenceable, U where V : BaseOpenApiReference, new()
     {
         /// <summary>
         /// Gets the resolved target object.
         /// </summary>
-        V? Target { get; }
-        
+        U? Target { get; }
+
         /// <summary>
         /// Gets the recursively resolved target object.
         /// </summary>
         T? RecursiveTarget { get; }
-        
+
         /// <summary>
         /// Copy the reference as a target element with overrides.
         /// </summary>
-        V CopyReferenceAsTargetElementWithOverrides(V source);
+        U CopyReferenceAsTargetElementWithOverrides(U source);
+    }
+    /// <summary>
+    /// A generic interface for OpenApiReferenceable objects that have a target.
+    /// </summary>
+    /// <typeparam name="V">The type for the reference holding the additional fields and annotations</typeparam>
+    public interface IOpenApiReferenceHolder<V> : IOpenApiReferenceHolder where V : BaseOpenApiReference, new()
+    {
+        /// <summary>
+        /// Reference object.
+        /// </summary>
+        V Reference { get; init; }
     }
     /// <summary>
     /// A generic interface for OpenApiReferenceable objects that have a target.
@@ -34,10 +46,5 @@
         /// Indicates if object is populated with data or is just a reference to the data
         /// </summary>
         bool UnresolvedReference { get; }
-
-        /// <summary>
-        /// Reference object.
-        /// </summary>
-        OpenApiReference Reference { get; init; }
     }
 }

src/Microsoft.OpenApi/Models/OpenApiReference.cs → src/Microsoft.OpenApi/Models/BaseOpenApiReference.cs

@@ -11,21 +11,8 @@
     /// <summary>
     /// A simple object to allow referencing other components in the specification, internally and externally.
     /// </summary>
-    public class OpenApiReference : IOpenApiSerializable, IOpenApiDescribedElement, IOpenApiSummarizedElement
+    public class BaseOpenApiReference : IOpenApiSerializable
     {
-        /// <summary>
-        /// A short summary which by default SHOULD override that of the referenced component.
-        /// If the referenced object-type does not allow a summary field, then this field has no effect.
-        /// </summary>
-        public string? Summary { get; set; }
-
-        /// <summary>
-        /// A description which by default SHOULD override that of the referenced component.
-        /// CommonMark syntax MAY be used for rich text representation.
-        /// If the referenced object-type does not allow a description field, then this field has no effect.
-        /// </summary>
-        public string? Description { get; set; }
-
         /// <summary>
         /// External resource in the reference.
         /// It maybe:
@@ -68,7 +55,7 @@
         /// <summary>
         /// The OpenApiDocument that is hosting the OpenApiReference instance. This is used to enable dereferencing the reference.
         /// </summary>
         public OpenApiDocument? HostDocument { get => hostDocument; init => hostDocument = value; }
 
         private string? _referenceV3;
         /// <summary>
@@ -143,45 +130,43 @@
         /// <summary>
         /// Parameterless constructor
         /// </summary>
-        public OpenApiReference() { }
+        public BaseOpenApiReference() { }
 
         /// <summary>
-        /// Initializes a copy instance of the <see cref="OpenApiReference"/> object
+        /// Initializes a copy instance of the <see cref="BaseOpenApiReference"/> object
         /// </summary>
-        public OpenApiReference(OpenApiReference reference)
+        public BaseOpenApiReference(BaseOpenApiReference reference)
         {
             Utils.CheckArgumentNull(reference);
-            Summary = reference.Summary;
-            Description = reference.Description;
             ExternalResource = reference.ExternalResource;
             Type = reference.Type;
             Id = reference.Id;
             HostDocument = reference.HostDocument;
         }
 
-        /// <summary>
-        /// Serialize <see cref="OpenApiReference"/> to Open Api v3.1.
-        /// </summary>
-        public void SerializeAsV31(IOpenApiWriter writer)
+        /// <inheritdoc/>
+        public virtual void SerializeAsV31(IOpenApiWriter writer)
         {
-            SerializeInternal(writer, w =>
-            {
-                // summary and description are in 3.1 but not in 3.0
-                w.WriteProperty(OpenApiConstants.Summary, Summary);
-                w.WriteProperty(OpenApiConstants.Description, Description);
-            });
+            SerializeInternal(writer, SerializeAdditionalV31Properties);
         }
 
         /// <summary>
-        /// Serialize <see cref="OpenApiReference"/> to Open Api v3.0.
+        /// Serialize additional properties for Open Api v3.1.
         /// </summary>
-        public void SerializeAsV3(IOpenApiWriter writer)
+        /// <param name="writer"></param>
+        protected virtual void SerializeAdditionalV31Properties(IOpenApiWriter writer)
+        {
+            // noop for the base type
+        }
+
+        /// <inheritdoc/>
+        public virtual void SerializeAsV3(IOpenApiWriter writer)
         {
             SerializeInternal(writer);
         }
 
         /// <summary>
-        /// Serialize <see cref="OpenApiReference"/>
+        /// Serialize <see cref="BaseOpenApiReference"/>
         /// </summary>
         private void SerializeInternal(IOpenApiWriter writer, Action<IOpenApiWriter>? callback = null)
         {
@@ -206,10 +191,8 @@
             writer.WriteEndObject();
         }
 
-        /// <summary>
-        /// Serialize <see cref="OpenApiReference"/> to Open Api v2.0.
-        /// </summary>
-        public void SerializeAsV2(IOpenApiWriter writer)
+        /// <inheritdoc/>
+        public virtual void SerializeAsV2(IOpenApiWriter writer)
         {
             Utils.CheckArgumentNull(writer);
 
@@ -291,23 +274,27 @@
             Utils.CheckArgumentNull(currentDocument);
             hostDocument ??= currentDocument;
         }
-        private static string? GetPropertyValueFromNode(JsonObject jsonObject, string key) =>
+        /// <summary>
+        /// Gets the property value from a JsonObject node.
+        /// </summary>
+        /// <param name="jsonObject">The object to get the value from</param>
+        /// <param name="key">The key of the property</param>
+        /// <returns>The property value</returns>
+        protected internal static string? GetPropertyValueFromNode(JsonObject jsonObject, string key) =>
         jsonObject.TryGetPropertyValue(key, out var valueNode) && valueNode is JsonValue valueCast && valueCast.TryGetValue<string>(out var strValue) ? strValue : null;
-        internal void SetSummaryAndDescriptionFromMapNode(MapNode mapNode)
+        internal virtual void SetMetadataFromMapNode(MapNode mapNode)
         {
-            var (description, summary) = mapNode.JsonNode switch {
-                JsonObject jsonObject => (GetPropertyValueFromNode(jsonObject, OpenApiConstants.Description),
-                                            GetPropertyValueFromNode(jsonObject, OpenApiConstants.Summary)),
-                _ => (null, null)
-            };
-            if (!string.IsNullOrEmpty(description))
-            {
-                Description = description;
-            }
-            if (!string.IsNullOrEmpty(summary))
-            {
-                Summary = summary;
-            }
+            if (mapNode.JsonNode is not JsonObject jsonObject) return;
+            SetAdditional31MetadataFromMapNode(jsonObject);
+        }
+
+        /// <summary>
+        /// Sets additional metadata from the map node.
+        /// </summary>
+        /// <param name="jsonObject">The object to get the data from</param>
+        protected virtual void SetAdditional31MetadataFromMapNode(JsonObject jsonObject)
+        {
+            // noop for the base type
         }
 
         internal void SetJsonPointerPath(string pointer, string nodeLocation)
@@ -319,11 +306,11 @@
             }
 
             // Absolute reference or anchor (e.g. "#/components/schemas/..." or full URL)
-            else if ((pointer.Contains('#') || pointer.StartsWith("http", StringComparison.OrdinalIgnoreCase)) 
+            else if ((pointer.Contains('#') || pointer.StartsWith("http", StringComparison.OrdinalIgnoreCase))
                 && !string.Equals(ReferenceV3, pointer, StringComparison.OrdinalIgnoreCase))
             {
                 ReferenceV3 = pointer;
-            }            
+            }
         }
 
         private static string ResolveRelativePointer(string nodeLocation, string relativeRef)

src/Microsoft.OpenApi/Models/JsonSchemaReference.cs

@@ -0,0 +1,139 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license.
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text.Json.Nodes;
+
+namespace Microsoft.OpenApi;
+
+/// <summary>
+/// Schema reference information that includes metadata annotations from JSON Schema 2020-12.
+/// This class extends OpenApiReference to provide schema-specific metadata override capabilities.
+/// </summary>
+public class JsonSchemaReference : OpenApiReferenceWithDescription
+{
+    /// <summary>
+    /// A default value which by default SHOULD override that of the referenced component.
+    /// If the referenced object-type does not allow a default field, then this field has no effect.
+    /// </summary>
+    public JsonNode? Default { get; set; }
+
+    /// <summary>
+    /// A title which by default SHOULD override that of the referenced component.
+    /// If the referenced object-type does not allow a title field, then this field has no effect.
+    /// </summary>
+    public string? Title { get; set; }
+
+    /// <summary>
+    /// Indicates whether the referenced component is deprecated.
+    /// If the referenced object-type does not allow a deprecated field, then this field has no effect.
+    /// </summary>
+    public bool? Deprecated { get; set; }
+
+    /// <summary>
+    /// Indicates whether the referenced component is read-only.
+    /// If the referenced object-type does not allow a readOnly field, then this field has no effect.
+    /// </summary>
+    public bool? ReadOnly { get; set; }
+
+    /// <summary>
+    /// Indicates whether the referenced component is write-only.
+    /// If the referenced object-type does not allow a writeOnly field, then this field has no effect.
+    /// </summary>
+    public bool? WriteOnly { get; set; }
+
+    /// <summary>
+    /// Example values which by default SHOULD override those of the referenced component.
+    /// If the referenced object-type does not allow examples, then this field has no effect.
+    /// </summary>
+    public IList<JsonNode>? Examples { get; set; }
+
+    /// <summary>
+    /// Parameterless constructor
+    /// </summary>
+    public JsonSchemaReference() { }
+
+    /// <summary>
+    /// Initializes a copy instance of the <see cref="JsonSchemaReference"/> object
+    /// </summary>
+    public JsonSchemaReference(JsonSchemaReference reference) : base(reference)
+    {
+        Utils.CheckArgumentNull(reference);
+        Default = reference.Default;
+        Title = reference.Title;
+        Deprecated = reference.Deprecated;
+        ReadOnly = reference.ReadOnly;
+        WriteOnly = reference.WriteOnly;
+        Examples = reference.Examples;
+    }
+
+    /// <inheritdoc/>
+    protected override void SerializeAdditionalV31Properties(IOpenApiWriter writer)
+    {
+        if (Type != ReferenceType.Schema) throw new InvalidOperationException(
+            $"JsonSchemaReference can only be serialized for ReferenceType.Schema, but was {Type}.");
+
+        base.SerializeAdditionalV31Properties(writer);        
+        // Additional schema metadata annotations in 3.1
+        writer.WriteOptionalObject(OpenApiConstants.Default, Default, (w, d) => w.WriteAny(d));
+        writer.WriteProperty(OpenApiConstants.Title, Title);
+        if (Deprecated.HasValue)
+        {
+            writer.WriteProperty(OpenApiConstants.Deprecated, Deprecated.Value, false);
+        }
+        if (ReadOnly.HasValue)
+        {
+            writer.WriteProperty(OpenApiConstants.ReadOnly, ReadOnly.Value, false);
+        }
+        if (WriteOnly.HasValue)
+        {
+            writer.WriteProperty(OpenApiConstants.WriteOnly, WriteOnly.Value, false);
+        }
+        if (Examples != null && Examples.Any())
+        {
+            writer.WriteOptionalCollection(OpenApiConstants.Examples, Examples, (w, e) => w.WriteAny(e));
+        }
+    }
+
+    /// <inheritdoc/>
+    protected override void SetAdditional31MetadataFromMapNode(JsonObject jsonObject)
+    {
+        base.SetAdditional31MetadataFromMapNode(jsonObject);
+
+        var title = GetPropertyValueFromNode(jsonObject, OpenApiConstants.Title);
+        if (!string.IsNullOrEmpty(title))
+        {
+            Title = title;
+        }
+
+        // Boolean properties
+        if (jsonObject.TryGetPropertyValue(OpenApiConstants.Deprecated, out var deprecatedNode) && deprecatedNode is JsonValue deprecatedValue && deprecatedValue.TryGetValue<bool>(out var deprecated))
+        {
+            Deprecated = deprecated;
+        }
+
+        if (jsonObject.TryGetPropertyValue(OpenApiConstants.ReadOnly, out var readOnlyNode) && readOnlyNode is JsonValue readOnlyValue && readOnlyValue.TryGetValue<bool>(out var readOnly))
+        {
+            ReadOnly = readOnly;
+        }
+
+        if (jsonObject.TryGetPropertyValue(OpenApiConstants.WriteOnly, out var writeOnlyNode) && writeOnlyNode is JsonValue writeOnlyValue && writeOnlyValue.TryGetValue<bool>(out var writeOnly))
+        {
+            WriteOnly = writeOnly;
+        }
+
+        // Default value
+        if (jsonObject.TryGetPropertyValue(OpenApiConstants.Default, out var defaultNode))
+        {
+            Default = defaultNode;
+        }
+
+        // Examples
+        if (jsonObject.TryGetPropertyValue(OpenApiConstants.Examples, out var examplesNode) && examplesNode is JsonArray examplesArray)
+        {
+            Examples = examplesArray.OfType<JsonNode>().ToList();
+        }
+    }
+}

src/Microsoft.OpenApi/Models/OpenApiDocument.cs

@@ -496,9 +496,9 @@ public void SetReferenceHostDocument()
         }
 
         /// <summary>
-        /// Load the referenced <see cref="IOpenApiReferenceable"/> object from a <see cref="OpenApiReference"/> object
+        /// Load the referenced <see cref="IOpenApiReferenceable"/> object from a <see cref="BaseOpenApiReference"/> object
         /// </summary>
-        internal T? ResolveReferenceTo<T>(OpenApiReference reference) where T : IOpenApiReferenceable
+        internal T? ResolveReferenceTo<T>(BaseOpenApiReference reference) where T : IOpenApiReferenceable
         {
 
             if (ResolveReference(reference, reference.IsExternal) is T result)
@@ -564,9 +564,9 @@ private static string ConvertByteArrayToString(byte[] hash)
         }
 
         /// <summary>
-        /// Load the referenced <see cref="IOpenApiReferenceable"/> object from a <see cref="OpenApiReference"/> object
+        /// Load the referenced <see cref="IOpenApiReferenceable"/> object from a <see cref="BaseOpenApiReference"/> object
         /// </summary>
-        internal IOpenApiReferenceable? ResolveReference(OpenApiReference? reference, bool useExternal)
+        internal IOpenApiReferenceable? ResolveReference(BaseOpenApiReference? reference, bool useExternal)
         {
             if (reference == null)
             {