opt into JsonApi per webapi endpoint

Saule/Http/JsonApiAttribute.cs

@@ -0,0 +1,38 @@
+using System;
+using System.Net.Http;
+using System.Web.Http.Filters;
+
+namespace Saule.Http
+{
+    /// <summary>
+    /// An optional attribute that can be used to opt an api into returning a JsonApi response.
+    /// </summary>
+    [AttributeUsage(AttributeTargets.Method | AttributeTargets.Class)]
+    public sealed class JsonApiAttribute : ActionFilterAttribute
+    {
+        /// <summary>
+        /// See base class documentation.
+        /// </summary>
+        /// <param name="context">The action context.</param>
+        public override void OnActionExecuted(HttpActionExecutedContext context)
+        {
+            var config = new JsonApiConfiguration();
+            JsonApiProcessor.ProcessRequest(context.Request, context.Response, config, requiresMediaType: false);
+
+            if (context.Exception != null)
+            {
+                return;
+            }
+
+            var responseContent = context.Response.Content as ObjectContent;
+            if (responseContent == null)
+            {
+                return;
+            }
+
+            var formatter = new JsonApiMediaTypeFormatter(context.Request, config);
+
+            context.Response.Content = new ObjectContent(responseContent.ObjectType, responseContent.Value, formatter);
+        }
+    }
+}

Saule/Http/JsonApiProcessor.cs

@@ -0,0 +1,43 @@
+using System.Linq;
+using System.Net;
+using System.Net.Http;
+using Saule.Serialization;
+
+namespace Saule.Http
+{
+    /// <summary>
+    /// Processes JSON API responses
+    /// </summary>
+    internal static class JsonApiProcessor
+    {
+        internal static void ProcessRequest(HttpRequestMessage request, HttpResponseMessage response, JsonApiConfiguration config, bool requiresMediaType)
+        {
+            var hasMediaType = request.Headers.Accept.Any(x => x.MediaType == Constants.MediaType);
+
+            var statusCode = (int)response.StatusCode;
+            if ((requiresMediaType && !hasMediaType) || (statusCode >= 400 && statusCode < 500))
+            {
+                // probably malformed request or not found
+                return;
+            }
+
+            var value = response.Content as ObjectContent;
+
+            if (config == null)
+            {
+                config = new JsonApiConfiguration();
+            }
+
+            var content = PreprocessingDelegatingHandler.PreprocessRequest(value?.Value, request, config);
+
+            if (content.ErrorContent != null)
+            {
+                response.StatusCode = ApiError.IsClientError(content.ErrorContent)
+                    ? HttpStatusCode.BadRequest
+                    : HttpStatusCode.InternalServerError;
+            }
+
+            request.Properties.Add(Constants.PropertyNames.PreprocessResult, content);
+        }
+    }
+}

Saule/Http/PreprocessingDelegatingHandler.cs

@@ -69,27 +69,8 @@ internal static PreprocessResult PreprocessRequest(
         protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
         {
             var result = await base.SendAsync(request, cancellationToken);
-            var hasMediaType = request.Headers.Accept.Any(x => x.MediaType == Constants.MediaType);
 
-            var statusCode = (int)result.StatusCode;
-            if (!hasMediaType || (statusCode >= 400 && statusCode < 500))
-            {
-                // probably malformed request or not found
-                return result;
-            }
-
-            var value = result.Content as ObjectContent;
-
-            var content = PreprocessRequest(value?.Value, request, _config);
-
-            if (content.ErrorContent != null)
-            {
-                result.StatusCode = ApiError.IsClientError(content.ErrorContent)
-                    ? HttpStatusCode.BadRequest
-                    : HttpStatusCode.InternalServerError;
-            }
-
-            request.Properties.Add(Constants.PropertyNames.PreprocessResult, content);
+            JsonApiProcessor.ProcessRequest(request, result, _config, requiresMediaType: true);
 
             return result;
         }

Saule/Saule.csproj

@@ -65,6 +65,8 @@
   <ItemGroup>
     <Compile Include="ApiResource.cs" />
     <Compile Include="Http\HandlesQueryAttribute.cs" />
+    <Compile Include="Http\JsonApiAttribute.cs" />
+    <Compile Include="Http\JsonApiProcessor.cs" />
     <Compile Include="Http\JsonApiQueryValueProvider.cs" />
     <Compile Include="Http\JsonApiQueryValueProviderFactory.cs" />
     <Compile Include="JsonApiSerializerOfT.cs" />

Tests/Controllers/CompaniesController.cs

@@ -37,6 +37,16 @@ public IEnumerable<Company> GetCompanies()
             return Get.Companies(100);
         }
 
+        [HttpGet]
+        [JsonApi]
+        [Paginated(PerPage = 12)]
+        [Route("v2/companies")]
+        [ReturnsResource(typeof(CompanyResource))]
+        public IEnumerable<Company> GetCompaniesV2()
+        {
+            return Get.Companies(100);
+        }
+
         [HttpGet]
         [Paginated(PerPage = 12)]
         [Route("companies/querypagesize")]

Tests/Helpers/ObsoleteSetupJsonApiServer.cs

@@ -22,7 +22,6 @@ public ObsoleteSetupJsonApiServer()
         internal ObsoleteSetupJsonApiServer(JsonApiMediaTypeFormatter formatter)
         {
             var config = new HttpConfiguration();
-            config.Formatters.Clear();
             config.Formatters.Add(formatter);
             config.MapHttpAttributeRoutes(new DefaultDirectRouteProvider());
 

Tests/Integration/ContentNegotiationTests.cs

@@ -1,10 +1,8 @@
 using System.IO;
-using System.Linq;
 using System.Net;
 using System.Net.Http;
 using System.Net.Http.Headers;
 using System.Threading.Tasks;
-using Newtonsoft.Json.Linq;
 using Saule;
 using Saule.Http;
 using Tests.Helpers;
@@ -26,6 +24,23 @@ public ObsoleteSetup(ObsoleteSetupJsonApiServer server)
                 _server = server;
             }
 
+            [Fact(DisplayName = "Servers MUST not respond with json api unless requested Content-Type is 'application/vnd.api+json' or action filter is set to 'JsonApiAttribute'")]
+            public async Task MustNotReturnJsonApiResponse()
+            {
+                var target = _server.GetClient();
+
+                var result = await target.GetAsync("api/companies/");
+                Assert.Equal("application/vnd.api+json", result.Content.Headers.ContentType.MediaType);
+
+                target.DefaultRequestHeaders.Clear();
+
+                result = await target.GetAsync("api/companies/");
+                Assert.Equal("application/json", result.Content.Headers.ContentType.MediaType);
+
+                result = await target.GetAsync("api/v2/companies/");
+                Assert.Equal("application/vnd.api+json", result.Content.Headers.ContentType.MediaType);
+            }
+
             [Theory(DisplayName = "Servers MUST return content type 'application/vnd.api+json'")]
             [InlineData(Paths.SingleResource)]
             [InlineData(Paths.ResourceCollection)]