feat(library): add missing json schema properties

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: baywet

src/Microsoft.OpenApi/Models/Interfaces/IOpenApiSchema.cs

@@ -260,7 +260,7 @@ public interface IOpenApiSchema : IOpenApiDescribedElement, IOpenApiReadOnlyExte
     /// <summary>
     /// Indicates whether unevaluated properties are allowed. When false, no unevaluated properties are permitted.
     /// Follow JSON Schema definition: https://json-schema.org/draft/2020-12/json-schema-core#name-unevaluatedproperties
-    /// Only serialized when false and UnevaluatedPropertiesSchema (from IOpenApiSchemaWithUnevaluatedProperties) is null.
+    /// Only serialized when false and UnevaluatedPropertiesSchema (from IOpenApiSchemaMissingProperties) is null.
     /// </summary>
     /// <remarks>
     /// NOTE: This property differs from the naming pattern of AdditionalPropertiesAllowed for binary compatibility reasons.

src/Microsoft.OpenApi/Models/Interfaces/IOpenApiSchemaMissingProperties.cs

@@ -0,0 +1,86 @@
+using System.Collections.Generic;
+
+namespace Microsoft.OpenApi;
+
+/// <summary>
+/// Compatibility interface for schema properties that cannot be added to <see cref="IOpenApiSchema"/>
+/// in the current major version without a breaking change.
+/// This interface provides access to those properties in contexts where callers need a typed model surface.
+/// </summary>
+/// <remarks>
+/// TODO: Remove this interface in the next major version and merge its content into IOpenApiSchema.
+/// </remarks>
+public interface IOpenApiSchemaMissingProperties
+{
+    /// <summary>
+    /// $anchor - identifies a plain-name location-independent fragment within the schema resource.
+    /// </summary>
+    public string? Anchor { get; }
+
+    /// <summary>
+    /// Indicates whether unevaluated properties are allowed. When false, no unevaluated properties are permitted.
+    /// Follow JSON Schema definition: https://json-schema.org/draft/2020-12/json-schema-core#name-unevaluatedproperties
+    /// Only serialized when false and <see cref="UnevaluatedPropertiesSchema"/> is null.
+    /// </summary>
+    /// <remarks>
+    /// NOTE: This property differs from the naming pattern of AdditionalPropertiesAllowed for binary compatibility reasons.
+    /// In the next major version, this will be renamed to UnevaluatedPropertiesAllowed.
+    /// TODO: Rename to UnevaluatedPropertiesAllowed in the next major version.
+    /// </remarks>
+    public bool UnevaluatedProperties { get; }
+
+    /// <summary>
+    /// Follow JSON Schema definition: https://json-schema.org/draft/2020-12/json-schema-core#name-unevaluatedproperties
+    /// This is a schema that unevaluated properties must validate against.
+    /// When serialized, this takes precedence over the <see cref="UnevaluatedProperties"/> boolean property.
+    /// </summary>
+    /// <remarks>
+    /// NOTE: This property differs from the naming pattern of AdditionalProperties/AdditionalPropertiesAllowed
+    /// for binary compatibility reasons. In the next major version:
+    /// - This property will be renamed to UnevaluatedProperties
+    /// - The current boolean UnevaluatedProperties property will be renamed to UnevaluatedPropertiesAllowed
+    ///
+    /// TODO: Rename this property to UnevaluatedProperties in the next major version.
+    /// </remarks>
+    public IOpenApiSchema? UnevaluatedPropertiesSchema { get; }
+
+    /// <summary>
+    /// contentEncoding - identifies the encoding of string content.
+    /// </summary>
+    public string? ContentEncoding { get; }
+
+    /// <summary>
+    /// contentMediaType - identifies the media type of string content.
+    /// </summary>
+    public string? ContentMediaType { get; }
+
+    /// <summary>
+    /// contentSchema - provides a schema that describes the decoded string content.
+    /// </summary>
+    public IOpenApiSchema? ContentSchema { get; }
+
+    /// <summary>
+    /// propertyNames - provides a schema that validates property names.
+    /// </summary>
+    public IOpenApiSchema? PropertyNames { get; }
+
+    /// <summary>
+    /// dependentSchemas - maps property names to schemas that are applied when that property is present.
+    /// </summary>
+    public IDictionary<string, IOpenApiSchema>? DependentSchemas { get; }
+
+    /// <summary>
+    /// if - applies a conditional schema that determines whether <see cref="Then"/> or <see cref="Else"/> should be evaluated.
+    /// </summary>
+    public IOpenApiSchema? If { get; }
+
+    /// <summary>
+    /// then - applies when <see cref="If"/> evaluates successfully.
+    /// </summary>
+    public IOpenApiSchema? Then { get; }
+
+    /// <summary>
+    /// else - applies when <see cref="If"/> does not evaluate successfully.
+    /// </summary>
+    public IOpenApiSchema? Else { get; }
+}

src/Microsoft.OpenApi/Models/Interfaces/IOpenApiSchemaWithUnevaluatedProperties.cs

@@ -1,3 +1,5 @@
+using System;
+
 namespace Microsoft.OpenApi;
 
 /// <summary>
@@ -13,6 +15,7 @@ namespace Microsoft.OpenApi;
 /// <remarks>
 /// TODO: Remove this interface in the next major version and merge its content into IOpenApiSchema.
 /// </remarks>
+[Obsolete("Use IOpenApiSchemaMissingProperties instead.")]
 public interface IOpenApiSchemaWithUnevaluatedProperties
 {
     /// <summary>

src/Microsoft.OpenApi/Models/OpenApiConstants.cs

@@ -90,6 +90,11 @@ public static class OpenApiConstants
         /// </summary>
         public const string Vocabulary = "$vocabulary";
 
+        /// <summary>
+        /// Field: Anchor
+        /// </summary>
+        public const string Anchor = "$anchor";
+
         /// <summary>
         /// Field: DynamicRef
         /// </summary>
@@ -131,9 +136,14 @@ public static class OpenApiConstants
         public const string UnevaluatedProperties = "unevaluatedProperties";
 
         /// <summary>
-        /// Extension: x-jsonschema-unevaluatedProperties
+        /// Extension: x-oai-unevaluatedProperties
+        /// </summary>
+        public const string UnevaluatedPropertiesExtension = "x-oai-unevaluatedProperties";
+
+        /// <summary>
+        /// Legacy extension: x-jsonschema-unevaluatedProperties
         /// </summary>
-        public const string UnevaluatedPropertiesExtension = "x-jsonschema-unevaluatedProperties";
+        public const string LegacyUnevaluatedPropertiesExtension = "x-jsonschema-unevaluatedProperties";
 
         /// <summary>
         /// Field: Version
@@ -535,11 +545,51 @@ public static class OpenApiConstants
         /// </summary>
         public const string PatternProperties = "patternProperties";
 
+        /// <summary>
+        /// Field: PropertyNames
+        /// </summary>
+        public const string PropertyNames = "propertyNames";
+
         /// <summary>
         /// Extension: x-jsonschema-patternProperties
         /// </summary>
         public const string PatternPropertiesExtension = "x-jsonschema-patternProperties";
 
+        /// <summary>
+        /// Field: DependentSchemas
+        /// </summary>
+        public const string DependentSchemas = "dependentSchemas";
+
+        /// <summary>
+        /// Field: If
+        /// </summary>
+        public const string If = "if";
+
+        /// <summary>
+        /// Field: Then
+        /// </summary>
+        public const string Then = "then";
+
+        /// <summary>
+        /// Field: Else
+        /// </summary>
+        public const string Else = "else";
+
+        /// <summary>
+        /// Field: ContentEncoding
+        /// </summary>
+        public const string ContentEncoding = "contentEncoding";
+
+        /// <summary>
+        /// Field: ContentMediaType
+        /// </summary>
+        public const string ContentMediaType = "contentMediaType";
+
+        /// <summary>
+        /// Field: ContentSchema
+        /// </summary>
+        public const string ContentSchema = "contentSchema";
+
         /// <summary>
         /// Field: AdditionalProperties
         /// </summary>
@@ -790,6 +840,51 @@ public static class OpenApiConstants
         /// </summary>
         public const string DependentRequired = "dependentRequired";
 
+        /// <summary>
+        /// Extension: x-oai-$anchor
+        /// </summary>
+        public const string AnchorExtension = "x-oai-$anchor";
+
+        /// <summary>
+        /// Extension: x-oai-propertyNames
+        /// </summary>
+        public const string PropertyNamesExtension = "x-oai-propertyNames";
+
+        /// <summary>
+        /// Extension: x-oai-dependentSchemas
+        /// </summary>
+        public const string DependentSchemasExtension = "x-oai-dependentSchemas";
+
+        /// <summary>
+        /// Extension: x-oai-if
+        /// </summary>
+        public const string IfExtension = "x-oai-if";
+
+        /// <summary>
+        /// Extension: x-oai-then
+        /// </summary>
+        public const string ThenExtension = "x-oai-then";
+
+        /// <summary>
+        /// Extension: x-oai-else
+        /// </summary>
+        public const string ElseExtension = "x-oai-else";
+
+        /// <summary>
+        /// Extension: x-oai-contentEncoding
+        /// </summary>
+        public const string ContentEncodingExtension = "x-oai-contentEncoding";
+
+        /// <summary>
+        /// Extension: x-oai-contentMediaType
+        /// </summary>
+        public const string ContentMediaTypeExtension = "x-oai-contentMediaType";
+
+        /// <summary>
+        /// Extension: x-oai-contentSchema
+        /// </summary>
+        public const string ContentSchemaExtension = "x-oai-contentSchema";
+
         #region V2.0
 
         /// <summary>