feat: Add support for ProblemDetails extensions

README.md

@@ -843,8 +843,11 @@ try
 }
 catch (ValidationApiException validationException)
 {
-   // handle validation here by using validationException.Content, 
+   // handle validation here by using validationException.Content,
    // which is type of ProblemDetails according to RFC 7807
+
+   // If the response contains additional properties on the problem details,
+   // they will be added to the validationException.Content.Extensions collection.
 }
 catch (ApiException exception)
 {

Refit.Tests/ResponseTests.cs

@@ -103,6 +103,42 @@ public async Task ThrowsValidationException()
             Assert.Equal("type", actualException.Content.Type);
         }
 
+        [Fact]
+        public async Task WhenProblemDetailsResponseContainsExtensions_ShouldHydrateExtensions()
+        {
+            var expectedContent = new
+            {
+                Detail = "detail",
+                Instance = "instance",
+                Status = 1,
+                Title = "title",
+                Type = "type",
+                Foo = "bar",
+                Baz = 123d,
+            };
+
+            var expectedResponse = new HttpResponseMessage(HttpStatusCode.BadRequest)
+            {
+                Content = new StringContent(JsonConvert.SerializeObject(expectedContent))
+            };
+
+            expectedResponse.Content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/problem+json");
+            mockHandler.Expect(HttpMethod.Get, "http://api/aliasTest")
+                .Respond(req => expectedResponse);
+
+            var actualException = await Assert.ThrowsAsync<ValidationApiException>(() => fixture.GetTestObject());
+            Assert.NotNull(actualException.Content);
+            Assert.Equal("detail", actualException.Content.Detail);
+            Assert.Equal("instance", actualException.Content.Instance);
+            Assert.Equal(1, actualException.Content.Status);
+            Assert.Equal("title", actualException.Content.Title);
+            Assert.Equal("type", actualException.Content.Type);
+
+            Assert.Collection(actualException.Content.Extensions,
+                kvp => Assert.Equal(new KeyValuePair<string, object>(nameof(expectedContent.Foo), expectedContent.Foo), kvp),
+                kvp => Assert.Equal(new KeyValuePair<string, object>(nameof(expectedContent.Baz), expectedContent.Baz), kvp));
+        }
+
         [Fact]
         public async Task BadRequestWithEmptyContent_ShouldReturnApiException()
         {

Refit/ProblemDetails.cs

@@ -1,4 +1,6 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
+using Newtonsoft.Json;
 
 namespace Refit
 {
@@ -12,6 +14,12 @@ public class ProblemDetails
         /// </summary>
         public Dictionary<string, string[]> Errors { get; set; } = new Dictionary<string, string[]>();
 
+        /// <summary>
+        /// Collection of ProblemDetails extensions
+        /// </summary>
+        [JsonExtensionData]
+        public IDictionary<string, object> Extensions { get; } = new Dictionary<string, object>(StringComparer.Ordinal);
+
         /// <summary>
         /// A URI reference that identifies the problem type.
         /// </summary>