From fa253cc25f67d6295a883539ce4ac1d3ec1a8cd3 Mon Sep 17 00:00:00 2001
From: Bart Koelman <10324372+bkoelman@users.noreply.github.com>
Date: Sun, 23 Feb 2025 23:30:55 +0100
Subject: [PATCH] Marshall JsonApiException thrown from JsonConverter such that
 the source pointer can be reconstructed

---
 .../JsonConverters/ResourceObjectConverter.cs |  21 +++
 .../Serialization/Request/JsonApiReader.cs    |   4 +
 .../NotSupportedExceptionExtensions.cs        |  91 +++++++++++
 .../ResourceObjectConverterTests.cs           |  47 +++++-
 .../SourcePointerInExceptionTests.cs          | 143 ++++++++++++++++++
 5 files changed, 300 insertions(+), 6 deletions(-)
 create mode 100644 src/JsonApiDotNetCore/Serialization/Request/NotSupportedExceptionExtensions.cs
 create mode 100644 test/JsonApiDotNetCoreTests/UnitTests/Serialization/Extensions/SourcePointerInExceptionTests.cs

diff --git a/src/JsonApiDotNetCore/Serialization/JsonConverters/ResourceObjectConverter.cs b/src/JsonApiDotNetCore/Serialization/JsonConverters/ResourceObjectConverter.cs
index 2f820175d2..8bc67c0196 100644
--- a/src/JsonApiDotNetCore/Serialization/JsonConverters/ResourceObjectConverter.cs
+++ b/src/JsonApiDotNetCore/Serialization/JsonConverters/ResourceObjectConverter.cs
@@ -1,7 +1,10 @@
+using System.Diagnostics.CodeAnalysis;
 using System.Reflection;
+using System.Runtime.ExceptionServices;
 using System.Text.Json;
 using JetBrains.Annotations;
 using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Errors;
 using JsonApiDotNetCore.Resources;
 using JsonApiDotNetCore.Resources.Annotations;
 using JsonApiDotNetCore.Serialization.Objects;
@@ -372,4 +375,22 @@ private protected virtual void WriteExtensionInAttributes(Utf8JsonWriter writer,
     private protected virtual void WriteExtensionInRelationships(Utf8JsonWriter writer, ResourceObject value)
     {
     }
+
+    /// <summary>
+    /// Throws a <see cref="JsonApiException" /> in such a way that <see cref="JsonApiReader" /> can reconstruct the source pointer.
+    /// </summary>
+    /// <param name="exception">
+    /// The <see cref="JsonApiException" /> to throw, which may contain a relative source pointer.
+    /// </param>
+    [DoesNotReturn]
+    [ContractAnnotation("=> halt")]
+    private protected static void CapturedThrow(JsonApiException exception)
+    {
+        ExceptionDispatchInfo.SetCurrentStackTrace(exception);
+
+        throw new NotSupportedException(null, exception)
+        {
+            Source = "System.Text.Json.Rethrowable"
+        };
+    }
 }
diff --git a/src/JsonApiDotNetCore/Serialization/Request/JsonApiReader.cs b/src/JsonApiDotNetCore/Serialization/Request/JsonApiReader.cs
index f565395969..9c0139d949 100644
--- a/src/JsonApiDotNetCore/Serialization/Request/JsonApiReader.cs
+++ b/src/JsonApiDotNetCore/Serialization/Request/JsonApiReader.cs
@@ -97,6 +97,10 @@ private Document DeserializeDocument(string requestBody)
             // https://github.com/dotnet/runtime/issues/50205#issuecomment-808401245
             throw new InvalidRequestBodyException(_options.IncludeRequestBodyInErrors ? requestBody : null, null, exception.Message, null, null, exception);
         }
+        catch (NotSupportedException exception) when (exception.HasJsonApiException())
+        {
+            throw exception.EnrichSourcePointer();
+        }
     }
 
     private void AssertHasDocument([SysNotNull] Document? document, string requestBody)
diff --git a/src/JsonApiDotNetCore/Serialization/Request/NotSupportedExceptionExtensions.cs b/src/JsonApiDotNetCore/Serialization/Request/NotSupportedExceptionExtensions.cs
new file mode 100644
index 0000000000..70e44f5730
--- /dev/null
+++ b/src/JsonApiDotNetCore/Serialization/Request/NotSupportedExceptionExtensions.cs
@@ -0,0 +1,91 @@
+using System.Text.Json.Serialization;
+using JsonApiDotNetCore.Errors;
+using JsonApiDotNetCore.Serialization.Objects;
+
+namespace JsonApiDotNetCore.Serialization.Request;
+
+/// <summary>
+/// A hacky approach to obtain the proper JSON:API source pointer from an exception thrown in a <see cref="JsonConverter" />.
+/// </summary>
+/// <remarks>
+/// <para>
+/// This method relies on the behavior at
+/// https://github.com/dotnet/runtime/blob/release/8.0/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonConverterOfT.ReadCore.cs#L100,
+/// which wraps a thrown <see cref="NotSupportedException" /> and adds the JSON path to the outer exception message, based on internal reader state.
+/// </para>
+/// <para>
+/// To take advantage of this, we expect a custom converter to throw a <see cref="NotSupportedException" /> with a specially-crafted
+/// <see cref="Exception.Source" /> and a nested <see cref="JsonApiException" /> containing a relative source pointer and a captured stack trace. Once
+/// all of that happens, this class extracts the added JSON path from the outer exception message and converts it to a JSON:API pointer to enrich the
+/// nested <see cref="JsonApiException" /> with.
+/// </para>
+/// </remarks>
+internal static class NotSupportedExceptionExtensions
+{
+    private const string LeadingText = " Path: ";
+    private const string TrailingText = " | LineNumber: ";
+
+    public static bool HasJsonApiException(this NotSupportedException exception)
+    {
+        return exception.InnerException is NotSupportedException { InnerException: JsonApiException };
+    }
+
+    public static JsonApiException EnrichSourcePointer(this NotSupportedException exception)
+    {
+        var jsonApiException = (JsonApiException)exception.InnerException!.InnerException!;
+        string? sourcePointer = GetSourcePointerFromMessage(exception.Message);
+
+        if (sourcePointer != null)
+        {
+            foreach (ErrorObject error in jsonApiException.Errors)
+            {
+                if (error.Source == null)
+                {
+                    error.Source = new ErrorSource
+                    {
+                        Pointer = sourcePointer
+                    };
+                }
+                else
+                {
+                    error.Source.Pointer = sourcePointer + '/' + error.Source.Pointer;
+                }
+            }
+        }
+
+        return jsonApiException;
+    }
+
+    private static string? GetSourcePointerFromMessage(string message)
+    {
+        string? jsonPath = ExtractJsonPathFromMessage(message);
+        return JsonPathToSourcePointer(jsonPath);
+    }
+
+    private static string? ExtractJsonPathFromMessage(string message)
+    {
+        int startIndex = message.IndexOf(LeadingText, StringComparison.Ordinal);
+
+        if (startIndex != -1)
+        {
+            int stopIndex = message.IndexOf(TrailingText, startIndex, StringComparison.Ordinal);
+
+            if (stopIndex != -1)
+            {
+                return message.Substring(startIndex + LeadingText.Length, stopIndex - startIndex - LeadingText.Length);
+            }
+        }
+
+        return null;
+    }
+
+    private static string? JsonPathToSourcePointer(string? jsonPath)
+    {
+        if (jsonPath != null && jsonPath.StartsWith('$'))
+        {
+            return jsonPath[1..].Replace('.', '/');
+        }
+
+        return null;
+    }
+}
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Extensions/ResourceObjectConverterTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Extensions/ResourceObjectConverterTests.cs
index 9dbdb5d68d..d5a63c0447 100644
--- a/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Extensions/ResourceObjectConverterTests.cs
+++ b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Extensions/ResourceObjectConverterTests.cs
@@ -1,8 +1,10 @@
+using System.Net;
 using System.Text;
 using System.Text.Json;
 using FluentAssertions;
 using JetBrains.Annotations;
 using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Errors;
 using JsonApiDotNetCore.Middleware;
 using JsonApiDotNetCore.Resources;
 using JsonApiDotNetCore.Resources.Annotations;
@@ -186,7 +188,16 @@ public void Throws_for_request_body_with_extension_in_attributes_when_extension_
         };
 
         // Assert
-        action.Should().ThrowExactly<JsonException>().WithMessage("Failure requested from attributes.");
+        JsonApiException? exception = action.Should().ThrowExactly<NotSupportedException>().WithInnerExceptionExactly<JsonApiException>().Which;
+
+        exception.StackTrace.Should().Contain(nameof(ExtensionAwareResourceObjectConverter));
+        exception.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = exception.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.BadRequest);
+        error.Title.Should().Be("Failure requested from attributes.");
+        error.Source.ShouldNotBeNull();
+        error.Source.Pointer.Should().Be("attributes/type-info:fail");
     }
 
     [Fact]
@@ -218,7 +229,16 @@ public void Throws_for_request_body_with_extension_in_relationships_when_extensi
         };
 
         // Assert
-        action.Should().ThrowExactly<JsonException>().WithMessage("Failure requested from relationships.");
+        JsonApiException? exception = action.Should().ThrowExactly<NotSupportedException>().WithInnerExceptionExactly<JsonApiException>().Which;
+
+        exception.StackTrace.Should().Contain(nameof(ExtensionAwareResourceObjectConverter));
+        exception.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = exception.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.BadRequest);
+        error.Title.Should().Be("Failure requested from relationships.");
+        error.Source.ShouldNotBeNull();
+        error.Source.Pointer.Should().Be("relationships/type-info:fail");
     }
 
     [Fact]
@@ -401,6 +421,7 @@ public void Writes_extension_in_response_body_when_extension_enabled_with_derive
     private sealed class ExtensionAwareResourceObjectConverter : ResourceObjectConverter
     {
         private const string ExtensionNamespace = "type-info";
+        private const string ExtensionName = "fail";
 
         private readonly IResourceGraph _resourceGraph;
         private readonly JsonApiRequestAccessor _requestAccessor;
@@ -420,11 +441,18 @@ public ExtensionAwareResourceObjectConverter(IResourceGraph resourceGraph, JsonA
         private protected override void ValidateExtensionInAttributes(string extensionNamespace, string extensionName, ResourceType resourceType,
             Utf8JsonReader reader)
         {
-            if (extensionNamespace == ExtensionNamespace && IsTypeInfoExtensionEnabled && extensionName == "fail")
+            if (extensionNamespace == ExtensionNamespace && IsTypeInfoExtensionEnabled && extensionName == ExtensionName)
             {
                 if (reader.GetBoolean())
                 {
-                    throw new JsonException("Failure requested from attributes.");
+                    CapturedThrow(new JsonApiException(new ErrorObject(HttpStatusCode.BadRequest)
+                    {
+                        Title = "Failure requested from attributes.",
+                        Source = new ErrorSource
+                        {
+                            Pointer = $"attributes/{ExtensionNamespace}:{ExtensionName}"
+                        }
+                    }));
                 }
 
                 return;
@@ -436,11 +464,18 @@ private protected override void ValidateExtensionInAttributes(string extensionNa
         private protected override void ValidateExtensionInRelationships(string extensionNamespace, string extensionName, ResourceType resourceType,
             Utf8JsonReader reader)
         {
-            if (extensionNamespace == ExtensionNamespace && IsTypeInfoExtensionEnabled && extensionName == "fail")
+            if (extensionNamespace == ExtensionNamespace && IsTypeInfoExtensionEnabled && extensionName == ExtensionName)
             {
                 if (reader.GetBoolean())
                 {
-                    throw new JsonException("Failure requested from relationships.");
+                    CapturedThrow(new JsonApiException(new ErrorObject(HttpStatusCode.BadRequest)
+                    {
+                        Title = "Failure requested from relationships.",
+                        Source = new ErrorSource
+                        {
+                            Pointer = $"relationships/{ExtensionNamespace}:{ExtensionName}"
+                        }
+                    }));
                 }
 
                 return;
diff --git a/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Extensions/SourcePointerInExceptionTests.cs b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Extensions/SourcePointerInExceptionTests.cs
new file mode 100644
index 0000000000..9216b4b896
--- /dev/null
+++ b/test/JsonApiDotNetCoreTests/UnitTests/Serialization/Extensions/SourcePointerInExceptionTests.cs
@@ -0,0 +1,143 @@
+using System.Net;
+using System.Text.Json;
+using FluentAssertions;
+using JetBrains.Annotations;
+using JsonApiDotNetCore.Configuration;
+using JsonApiDotNetCore.Errors;
+using JsonApiDotNetCore.Resources;
+using JsonApiDotNetCore.Serialization.JsonConverters;
+using JsonApiDotNetCore.Serialization.Objects;
+using JsonApiDotNetCore.Serialization.Request;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Logging.Abstractions;
+using TestBuildingBlocks;
+using Xunit;
+
+namespace JsonApiDotNetCoreTests.UnitTests.Serialization.Extensions;
+
+public sealed class SourcePointerInExceptionTests
+{
+    private const string RequestBody = """
+        {
+          "data": {
+            "type": "testResources",
+            "attributes": {
+              "ext-namespace:ext-name": "ignored"
+            }
+          }
+        }
+        """;
+
+    [Fact]
+    public async Task Adds_source_pointer_to_JsonApiException_thrown_from_JsonConverter()
+    {
+        // Arrange
+        const string? relativeSourcePointer = null;
+
+        var options = new JsonApiOptions();
+        IResourceGraph resourceGraph = new ResourceGraphBuilder(options, NullLoggerFactory.Instance).Add<TestResource, long>().Build();
+        var converter = new ThrowingResourceObjectConverter(resourceGraph, relativeSourcePointer);
+        var reader = new FakeJsonApiReader(RequestBody, options, converter);
+        var httpContext = new DefaultHttpContext();
+
+        // Act
+        Func<Task> action = async () => await reader.ReadAsync(httpContext.Request);
+
+        // Assert
+        JsonApiException? exception = (await action.Should().ThrowExactlyAsync<JsonApiException>()).Which;
+
+        exception.StackTrace.Should().Contain(nameof(ThrowingResourceObjectConverter));
+        exception.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = exception.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.UnprocessableEntity);
+        error.Title.Should().Be("Extension error");
+        error.Source.ShouldNotBeNull();
+        error.Source.Pointer.Should().Be("/data");
+    }
+
+    [Fact]
+    public async Task Makes_source_pointer_absolute_in_JsonApiException_thrown_from_JsonConverter()
+    {
+        // Arrange
+        const string relativeSourcePointer = "relative/path";
+
+        var options = new JsonApiOptions();
+        IResourceGraph resourceGraph = new ResourceGraphBuilder(options, NullLoggerFactory.Instance).Add<TestResource, long>().Build();
+        var converter = new ThrowingResourceObjectConverter(resourceGraph, relativeSourcePointer);
+        var reader = new FakeJsonApiReader(RequestBody, options, converter);
+        var httpContext = new DefaultHttpContext();
+
+        // Act
+        Func<Task> action = async () => await reader.ReadAsync(httpContext.Request);
+
+        // Assert
+        JsonApiException? exception = (await action.Should().ThrowExactlyAsync<JsonApiException>()).Which;
+
+        exception.StackTrace.Should().Contain(nameof(ThrowingResourceObjectConverter));
+        exception.Errors.ShouldHaveCount(1);
+
+        ErrorObject error = exception.Errors[0];
+        error.StatusCode.Should().Be(HttpStatusCode.UnprocessableEntity);
+        error.Title.Should().Be("Extension error");
+        error.Source.ShouldNotBeNull();
+        error.Source.Pointer.Should().Be("/data/relative/path");
+    }
+
+    [UsedImplicitly(ImplicitUseTargetFlags.Members)]
+    private sealed class TestResource : Identifiable<long>;
+
+    private sealed class ThrowingResourceObjectConverter(IResourceGraph resourceGraph, string? relativeSourcePointer)
+        : ResourceObjectConverter(resourceGraph)
+    {
+        private readonly string? _relativeSourcePointer = relativeSourcePointer;
+
+        private protected override void ValidateExtensionInAttributes(string extensionNamespace, string extensionName, ResourceType resourceType,
+            Utf8JsonReader reader)
+        {
+            var exception = new JsonApiException(new ErrorObject(HttpStatusCode.UnprocessableEntity)
+            {
+                Title = "Extension error"
+            });
+
+            if (_relativeSourcePointer != null)
+            {
+                exception.Errors[0].Source = new ErrorSource
+                {
+                    Pointer = _relativeSourcePointer
+                };
+            }
+
+            CapturedThrow(exception);
+        }
+    }
+
+    private sealed class FakeJsonApiReader : IJsonApiReader
+    {
+        private readonly string _requestBody;
+
+        private readonly JsonSerializerOptions _serializerOptions;
+
+        public FakeJsonApiReader(string requestBody, JsonApiOptions options, ResourceObjectConverter converter)
+        {
+            _requestBody = requestBody;
+
+            _serializerOptions = new JsonSerializerOptions(options.SerializerOptions);
+            _serializerOptions.Converters.Add(converter);
+        }
+
+        public Task<object?> ReadAsync(HttpRequest httpRequest)
+        {
+            try
+            {
+                JsonSerializer.Deserialize<Document>(_requestBody, _serializerOptions);
+            }
+            catch (NotSupportedException exception) when (exception.HasJsonApiException())
+            {
+                throw exception.EnrichSourcePointer();
+            }
+
+            return Task.FromResult<object?>(null);
+        }
+    }
+}

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