Added support for custom extensions

src/Microsoft.OpenApi.Readers/OpenApiReaderSettings.cs

@@ -0,0 +1,23 @@
+using Microsoft.OpenApi.Any;
+using Microsoft.OpenApi.Interfaces;
+using Microsoft.OpenApi.Readers.ParseNodes;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Microsoft.OpenApi.Readers
+{
+    /// <summary>
+    /// Configuration settings to control how OpenAPI documents are parsed
+    /// </summary>
+    public class OpenApiReaderSettings
+    {
+        /// <summary>
+        /// Dictionary of parsers for converting extensions into strongly typed classes
+        /// </summary>
+        public Dictionary<string, Func<IOpenApiAny , IOpenApiExtension>> ExtensionParsers { get; set; } = new Dictionary<string, Func<IOpenApiAny, IOpenApiExtension>>();
+
+    }
+}

src/Microsoft.OpenApi.Readers/OpenApiStreamReader.cs

@@ -15,7 +15,17 @@ namespace Microsoft.OpenApi.Readers
     /// </summary>
     public class OpenApiStreamReader : IOpenApiReader<Stream, OpenApiDiagnostic>
     {
+        private OpenApiReaderSettings _settings;
 
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="settings"></param>
+        public OpenApiStreamReader(OpenApiReaderSettings settings = null)
+        {
+            _settings = settings ?? new OpenApiReaderSettings();
+
+        }
         /// <summary>
         /// Reads the stream input and parses it into an Open API document.
         /// </summary>
@@ -38,7 +48,10 @@ public OpenApiDocument Read(Stream input, out OpenApiDiagnostic diagnostic)
                 return new OpenApiDocument();
             }
 
-            context = new ParsingContext();
+            context = new ParsingContext
+            {
+                ExtensionParsers = _settings.ExtensionParsers
+            };
             return context.Parse(yamlDocument, diagnostic);
         }
 

src/Microsoft.OpenApi.Readers/OpenApiStringReader.cs

@@ -12,6 +12,17 @@ namespace Microsoft.OpenApi.Readers
     /// </summary>
     public class OpenApiStringReader : IOpenApiReader<string, OpenApiDiagnostic>
     {
+        private readonly OpenApiReaderSettings _settings;
+
+        /// <summary>
+        /// Constructor tha allows reader to use non-default settings
+        /// </summary>
+        /// <param name="settings"></param>
+        public OpenApiStringReader(OpenApiReaderSettings settings = null)
+        {
+            _settings = settings ?? new OpenApiReaderSettings(); 
+        }
+
         /// <summary>
         /// Reads the string input and parses it into an Open API document.
         /// </summary>
@@ -24,7 +35,7 @@ public OpenApiDocument Read(string input, out OpenApiDiagnostic diagnostic)
                 writer.Flush();
                 memoryStream.Position = 0;
 
-                return new OpenApiStreamReader().Read(memoryStream, out diagnostic);
+                return new OpenApiStreamReader(_settings).Read(memoryStream, out diagnostic);
             }
         }
     }

src/Microsoft.OpenApi.Readers/ParsingContext.cs

@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using Microsoft.OpenApi.Any;
 using Microsoft.OpenApi.Interfaces;
 using Microsoft.OpenApi.Models;
 using Microsoft.OpenApi.Readers.Interface;
@@ -23,6 +24,9 @@ public class ParsingContext
         private readonly Dictionary<string, IOpenApiReferenceable> _referenceStore = new Dictionary<string, IOpenApiReferenceable>();
         private readonly Dictionary<string, object> _tempStorage = new Dictionary<string, object>();
         private IOpenApiVersionService _versionService;
+
+        internal Dictionary<string, Func<IOpenApiAny, IOpenApiExtension>> ExtensionParsers { get; set; }  = new Dictionary<string, Func<IOpenApiAny, IOpenApiExtension>>();
+
         internal RootNode RootNode { get; set; }
         internal List<OpenApiTag> Tags { get; private set; } = new List<OpenApiTag>();
 
@@ -61,6 +65,7 @@ internal OpenApiDocument Parse(YamlDocument yamlDocument, OpenApiDiagnostic diag
             return doc;
         }
 
+
         /// <summary>
         /// Gets the version of the Open API document.
         /// </summary>

src/Microsoft.OpenApi.Readers/V3/OpenApiDocumentDeserializer.cs

@@ -2,7 +2,9 @@
 // Licensed under the MIT license. 
 
 using System.Collections.Generic;
+using Microsoft.OpenApi.Any;
 using Microsoft.OpenApi.Extensions;
+using Microsoft.OpenApi.Interfaces;
 using Microsoft.OpenApi.Models;
 using Microsoft.OpenApi.Readers.ParseNodes;
 
@@ -50,5 +52,17 @@ public static OpenApiDocument LoadOpenApi(RootNode rootNode)
 
             return openApidoc;
         }
+
+
+        public static IOpenApiExtension LoadExtension(string name, ParseNode node)
+        {
+            if (node.Context.ExtensionParsers.TryGetValue(name, out var parser)) {
+                return parser(node.CreateAny());
+            }
+            else
+            {
+                return node.CreateAny();
+            }
+        }
     }
 }

src/Microsoft.OpenApi.Readers/V3/OpenApiInfoDeserializer.cs

@@ -57,7 +57,7 @@ internal static partial class OpenApiV3Deserializer
 
         public static PatternFieldMap<OpenApiInfo> InfoPatternFields = new PatternFieldMap<OpenApiInfo>
         {
-            {s => s.StartsWith("x-"), (o, k, n) => o.AddExtension(k, n.CreateAny())}
+            {s => s.StartsWith("x-"), (o, k, n) => o.Extensions.Add(k,LoadExtension(k, n))}
         };
 
         public static OpenApiInfo LoadInfo(ParseNode node)

src/Microsoft.OpenApi/Any/IOpenApiAny.cs

@@ -8,7 +8,7 @@ namespace Microsoft.OpenApi.Any
     /// <summary>
     /// Base interface for all the types that represent Open API Any.
     /// </summary>
-    public interface IOpenApiAny : IOpenApiElement
+    public interface IOpenApiAny : IOpenApiElement, IOpenApiExtension
     {
         /// <summary>
         /// Type of an <see cref="IOpenApiAny"/>.

src/Microsoft.OpenApi/Any/OpenApiArray.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license. 
 
+using Microsoft.OpenApi.Writers;
 using System.Collections.Generic;
 
 namespace Microsoft.OpenApi.Any
@@ -14,5 +15,22 @@ public class OpenApiArray : List<IOpenApiAny>, IOpenApiAny
         /// The type of <see cref="IOpenApiAny"/>
         /// </summary>
         public AnyType AnyType { get; } = AnyType.Array;
+
+        /// <summary>
+        /// Write out contents of OpenApiArray to passed writer
+        /// </summary>
+        /// <param name="writer">Instance of JSON or YAML writer.</param>
+        public void Write(IOpenApiWriter writer)
+        {
+            writer.WriteStartArray();
+
+            foreach (var item in this)
+            {
+                writer.WriteAny(item);
+            }
+
+            writer.WriteEndArray();
+
+        }
     }
 }

src/Microsoft.OpenApi/Any/OpenApiNull.cs

@@ -1,6 +1,8 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license. 
 
+using Microsoft.OpenApi.Writers;
+
 namespace Microsoft.OpenApi.Any
 {
     /// <summary>
@@ -12,5 +14,14 @@ public class OpenApiNull : IOpenApiAny
         /// The type of <see cref="IOpenApiAny"/>
         /// </summary>
         public AnyType AnyType { get; } = AnyType.Null;
+
+        /// <summary>
+        /// Write out null representation
+        /// </summary>
+        /// <param name="writer"></param>
+        public void Write(IOpenApiWriter writer)
+        {
+            writer.WriteAny(this);
+        }
     }
 }

src/Microsoft.OpenApi/Any/OpenApiObject.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. 
 
 using System.Collections.Generic;
+using Microsoft.OpenApi.Writers;
 
 namespace Microsoft.OpenApi.Any
 {
@@ -14,5 +15,23 @@ public class OpenApiObject : Dictionary<string, IOpenApiAny>, IOpenApiAny
         /// Type of <see cref="IOpenApiAny"/>.
         /// </summary>
         public AnyType AnyType { get; } = AnyType.Object;
+
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="writer"></param>
+        public void Write(IOpenApiWriter writer)
+        {
+            writer.WriteStartObject();
+
+            foreach (var item in this)
+            {
+                writer.WritePropertyName(item.Key);
+                writer.WriteAny(item.Value);
+            }
+
+            writer.WriteEndObject();
+
+        }
     }
 }

src/Microsoft.OpenApi/Any/OpenApiPrimitive.cs

@@ -1,6 +1,10 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license. 
 
+using Microsoft.OpenApi.Exceptions;
+using Microsoft.OpenApi.Properties;
+using Microsoft.OpenApi.Writers;
+
 namespace Microsoft.OpenApi.Any
 {
     /// <summary>
@@ -32,5 +36,77 @@ public OpenApiPrimitive(T value)
         /// Value of this <see cref="IOpenApiPrimitive"/>
         /// </summary>
         public T Value { get; }
+
+        /// <summary>
+        /// Write out content of primitive element
+        /// </summary>
+        /// <param name="writer"></param>
+        public void Write(IOpenApiWriter writer)
+        {
+            switch (this.PrimitiveType)
+            {
+                case PrimitiveType.Integer:
+                    var intValue = (OpenApiInteger)(IOpenApiPrimitive)this;
+                    writer.WriteValue(intValue.Value);
+                    break;
+
+                case PrimitiveType.Long:
+                    var longValue = (OpenApiLong)(IOpenApiPrimitive)this;
+                    writer.WriteValue(longValue.Value);
+                    break;
+
+                case PrimitiveType.Float:
+                    var floatValue = (OpenApiFloat)(IOpenApiPrimitive)this;
+                    writer.WriteValue(floatValue.Value);
+                    break;
+
+                case PrimitiveType.Double:
+                    var doubleValue = (OpenApiDouble)(IOpenApiPrimitive)this;
+                    writer.WriteValue(doubleValue.Value);
+                    break;
+
+                case PrimitiveType.String:
+                    var stringValue = (OpenApiString)(IOpenApiPrimitive)this;
+                    writer.WriteValue(stringValue.Value);
+                    break;
+
+                case PrimitiveType.Byte:
+                    var byteValue = (OpenApiByte)(IOpenApiPrimitive)this;
+                    writer.WriteValue(byteValue.Value);
+                    break;
+
+                case PrimitiveType.Binary:
+                    var binaryValue = (OpenApiBinary)(IOpenApiPrimitive)this;
+                    writer.WriteValue(binaryValue.Value);
+                    break;
+
+                case PrimitiveType.Boolean:
+                    var boolValue = (OpenApiBoolean)(IOpenApiPrimitive)this;
+                    writer.WriteValue(boolValue.Value);
+                    break;
+
+                case PrimitiveType.Date:
+                    var dateValue = (OpenApiDate)(IOpenApiPrimitive)this;
+                    writer.WriteValue(dateValue.Value);
+                    break;
+
+                case PrimitiveType.DateTime:
+                    var dateTimeValue = (OpenApiDateTime)(IOpenApiPrimitive)this;
+                    writer.WriteValue(dateTimeValue.Value);
+                    break;
+
+                case PrimitiveType.Password:
+                    var passwordValue = (OpenApiPassword)(IOpenApiPrimitive)this;
+                    writer.WriteValue(passwordValue.Value);
+                    break;
+
+                default:
+                    throw new OpenApiWriterException(
+                        string.Format(
+                            SRResource.PrimitiveTypeNotSupported,
+                            this.PrimitiveType));
+            }
+
+        }
     }
 }

src/Microsoft.OpenApi/Extensions/OpenApiExtensibleExtensions.cs

@@ -41,5 +41,6 @@ public static void AddExtension<T>(this T element, string name, IOpenApiAny any)
 
             element.Extensions[name] = any ?? throw Error.ArgumentNull(nameof(any));
         }
+
     }
 }

src/Microsoft.OpenApi/Interfaces/IOpenApiExtensible.cs

@@ -14,6 +14,6 @@ public interface IOpenApiExtensible : IOpenApiElement
         /// <summary>
         /// Specification extensions.
         /// </summary>
-        IDictionary<string, IOpenApiAny> Extensions { get; set; }
+        IDictionary<string, IOpenApiExtension> Extensions { get; set; }
     }
 }

src/Microsoft.OpenApi/Interfaces/IOpenApiExtension.cs

@@ -0,0 +1,21 @@
+using Microsoft.OpenApi.Writers;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Microsoft.OpenApi.Interfaces
+{
+    /// <summary>
+    /// Interface requuired for implementing any custom extension
+    /// </summary>
+    public interface IOpenApiExtension
+    {
+        /// <summary>
+        /// Write out contents of custom extension
+        /// </summary>
+        /// <param name="writer"></param>
+        void Write(IOpenApiWriter writer);
+    }
+}

src/Microsoft.OpenApi/Models/OpenApiCallback.cs

@@ -28,7 +28,7 @@ public class OpenApiCallback : IOpenApiSerializable, IOpenApiReferenceable, IOpe
         /// <summary>
         /// This object MAY be extended with Specification Extensions.
         /// </summary>
-        public IDictionary<string, IOpenApiAny> Extensions { get; set; } = new Dictionary<string, IOpenApiAny>();
+        public IDictionary<string, IOpenApiExtension> Extensions { get; set; } = new Dictionary<string, IOpenApiExtension>();
 
         /// <summary>
         /// Add a <see cref="OpenApiPathItem"/> into the <see cref="PathItems"/>.

src/Microsoft.OpenApi/Models/OpenApiComponents.cs

@@ -64,7 +64,7 @@ public class OpenApiComponents : IOpenApiSerializable, IOpenApiExtensible
         /// <summary>
         /// This object MAY be extended with Specification Extensions.
         /// </summary>
-        public IDictionary<string, IOpenApiAny> Extensions { get; set; } = new Dictionary<string, IOpenApiAny>();
+        public IDictionary<string, IOpenApiExtension> Extensions { get; set; } = new Dictionary<string, IOpenApiExtension>();
 
         /// <summary>
         /// Serialize <see cref="OpenApiComponents"/> to Open Api v3.0.

src/Microsoft.OpenApi/Models/OpenApiContact.cs

@@ -33,7 +33,7 @@ public class OpenApiContact : IOpenApiSerializable, IOpenApiExtensible
         /// <summary>
         /// This object MAY be extended with Specification Extensions.
         /// </summary>
-        public IDictionary<string, IOpenApiAny> Extensions { get; set; } = new Dictionary<string, IOpenApiAny>();
+        public IDictionary<string, IOpenApiExtension> Extensions { get; set; } = new Dictionary<string, IOpenApiExtension>();
 
         /// <summary>
         /// Serialize <see cref="OpenApiContact"/> to Open Api v3.0