#1397 Add polymorphism support to generated OpenAPI json and UI using Swashbuckle:

- Working prototype for polymorphic object passing through API.
- Added filters for adding discriminator to the schema;
- Each polymorphic type should have property "Type" containig its real type;
- Filters added to module sawgger docs and general one;
TODO:
- Need to add Registrar for registering polymorphic types and use it inside Swagger config;
- Possible to add interface ISupportPolymorphicAPI with string Type => GetType() property.

Author: yecli

VirtoCommerce.Platform.Web/Controllers/Api/PolyController.cs

@@ -0,0 +1,65 @@
+using System.Collections.Generic;
+using System.Web.Http;
+using System.Web.Http.Description;
+
+namespace VirtoCommerce.Platform.Web.Controllers.Api
+{
+    [RoutePrefix("api/platform/poly")]
+    public class PolyController : ApiController
+    {
+        public PolyController()
+        {
+        }
+
+        [HttpGet]
+        [Route("")]
+        [ResponseType(typeof(BaseClass[]))]
+        public IHttpActionResult GetPolyTypes()
+        {
+            //return Ok(new BaseClassGroup
+            //{
+            //    Name = "GroupObject2",
+            //    AdditionalInfo = "Add info on this object",
+            //    Items = new[]
+            //    {
+            //            new  BaseClass { Name = "ChildItem1"},
+            //            new  BaseClass { Name = "ChildItem2"},
+            //        }
+            //});
+            return Ok(new BaseClass[]
+            {
+                new BaseClass { Name = "BaseObject1"},
+                new BaseClass { Name = "BaseObject2"},
+            new BaseClassGroup
+            {
+                Name = "GroupObject2",
+                AdditionalInfo = "Add info on this object",
+                Items = new[]
+                {
+                        new  BaseClass { Name = "ChildItem1"},
+                        new  BaseClass { Name = "ChildItem2"},
+                    }
+            },
+            });
+        }
+    }
+
+    public class BaseClass
+    {
+        public string Name { get; set; }
+        public string Type
+        {
+            get
+            {
+                return GetType().Name;
+            }
+        }
+    }
+
+    public class BaseClassGroup : BaseClass
+    {
+        public ICollection<BaseClass> Items { get; set; }
+        public string AdditionalInfo { get; set; }
+    }
+
+}

VirtoCommerce.Platform.Web/Swagger/PolymorphismSchemaFilter.cs

@@ -0,0 +1,84 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using Swashbuckle.Swagger;
+
+namespace VirtoCommerce.Platform.Web.Swagger
+{
+
+    public class PolymorphismSchemaFilter<T> : ISchemaFilter
+    {
+        private readonly Lazy<HashSet<Type>> derivedTypes = new Lazy<HashSet<Type>>(Init);
+
+        private static HashSet<Type> Init()
+        {
+            var abstractType = typeof(T);
+            var dTypes = abstractType.Assembly
+                                     .GetTypes()
+                                     .Where(x => abstractType != x && abstractType.IsAssignableFrom(x));
+
+            var result = new HashSet<Type>();
+
+            foreach (var item in dTypes)
+                result.Add(item);
+
+            return result;
+        }
+
+        [CLSCompliant(false)]
+        public void Apply(Schema schema, SchemaRegistry schemaRegistry, Type type)
+        {
+            if (!derivedTypes.Value.Contains(type))
+                return;
+
+            var clonedSchema = new Schema
+            {
+                properties = schema.properties,
+                type = schema.type,
+                required = schema.required
+            };
+
+            //schemaRegistry.Definitions[typeof(T).Name]; does not work correctly in SwashBuckle
+            var parentSchema = new Schema { @ref = "#/definitions/" + typeof(T).Name };
+
+            schema.allOf = new List<Schema> { parentSchema, clonedSchema };
+
+            //reset properties for they are included in allOf, should be null but code does not handle it
+            schema.properties = new Dictionary<string, Schema>();
+        }
+    }
+
+
+    public class PolymorphismDocumentFilter<T> : IDocumentFilter
+    {
+        [CLSCompliant(false)]
+        public void Apply(SwaggerDocument swaggerDoc, SchemaRegistry schemaRegistry, System.Web.Http.Description.IApiExplorer apiExplorer)
+        {
+            RegisterSubClasses(schemaRegistry, typeof(T));
+        }
+
+
+        private static void RegisterSubClasses(SchemaRegistry schemaRegistry, Type abstractType)
+        {
+            const string discriminatorName = "type";
+
+            var typeName = schemaRegistry.Definitions.ContainsKey(abstractType.FullName) ? abstractType.FullName : abstractType.FriendlyId();
+            var parentSchema = schemaRegistry.Definitions[typeName];
+
+            //set up a discriminator property (it must be required)
+            parentSchema.discriminator = discriminatorName;
+            parentSchema.required = new List<string> { discriminatorName };
+
+            if (!parentSchema.properties.ContainsKey(discriminatorName))
+                parentSchema.properties.Add(discriminatorName, new Schema { type = "string" });
+
+            //register all subclasses
+            var derivedTypes = abstractType.Assembly
+                                           .GetTypes()
+                                           .Where(x => abstractType != x && abstractType.IsAssignableFrom(x));
+
+            foreach (var item in derivedTypes)
+                schemaRegistry.GetOrRegister(item);
+        }
+    }
+}

VirtoCommerce.Platform.Web/Swagger/SwaggerConfig.cs

@@ -12,6 +12,7 @@
 using Swashbuckle.Swagger;
 using VirtoCommerce.Platform.Core.Modularity;
 using VirtoCommerce.Platform.Core.Settings;
+using VirtoCommerce.Platform.Web.Controllers.Api;
 
 namespace VirtoCommerce.Platform.Web.Swagger
 {
@@ -61,6 +62,9 @@ public static void RegisterRoutes(IUnityContainer container)
                     .Replace(',', '-')
                 );
 
+                c.DocumentFilter<PolymorphismDocumentFilter<BaseClass>>();
+                c.SchemaFilter<PolymorphismSchemaFilter<BaseClass>>();
+
                 ApplyCommonSwaggerConfiguration(c, container, string.Empty, xmlCommentsFilePaths);
             })
             .EnableSwaggerUi(routePrefix + "docs/ui/{*assetPath}", c =>
@@ -97,6 +101,11 @@ private static void EnableSwagger(string moduleName, HttpConfiguration httpConfi
 
                 ApplyCommonSwaggerConfiguration(c, container, moduleName, xmlCommentsFilePaths);
                 c.OperationFilter(() => new ModuleTagsFilter(moduleName));
+                if (moduleName.Equals("VirtoCommerce.Platform", StringComparison.InvariantCultureIgnoreCase))
+                {
+                    c.DocumentFilter<PolymorphismDocumentFilter<BaseClass>>();
+                    c.SchemaFilter<PolymorphismSchemaFilter<BaseClass>>();
+                }
             });
         }
 

VirtoCommerce.Platform.Web/VirtoCommerce.Platform.Web.csproj

@@ -337,6 +337,7 @@
     <Compile Include="Controllers\AiHandleErrorAttribute.cs" />
     <Compile Include="Controllers\Api\ChangeLogController.cs" />
     <Compile Include="Controllers\Api\LicensingController.cs" />
+    <Compile Include="Controllers\Api\PolyController.cs" />
     <Compile Include="Controllers\Api\ProfilesController.cs" />
     <Compile Include="Controllers\Api\AssetEntryController.cs" />
     <Compile Include="Controllers\ExternalLoginController.cs" />
@@ -455,6 +456,7 @@
     <Compile Include="Swagger\ModuleTagsFilter.cs" />
     <Compile Include="Swagger\AssignOAuth2SecurityOperationFilter.cs" />
     <Compile Include="Swagger\OptionalParametersFilter.cs" />
+    <Compile Include="Swagger\PolymorphismSchemaFilter.cs" />
     <Compile Include="Swagger\SwaggerConfig.cs" />
     <Compile Include="Swagger\TagsFilter.cs" />
     <Compile Include="Swagger\UploadFileAttribute.cs" />