Add ErrorModes to HotChocolate

src/HotChocolate/Adapters/src/Adapters.OpenApi.Core/Execution/DynamicEndpointMiddleware.cs

@@ -69,7 +69,7 @@ await Results.Problem(
 
             var requestBuilder = OperationRequestBuilder.New()
                 .SetDocument(endpointDescriptor.Document)
-                .SetErrorHandlingMode(ErrorHandlingMode.Halt)
+                .SetErrorHandlingMode(ErrorHandlingMode.Propagate)
                 .SetVariableValues(variables);
 
             await session.OnCreateAsync(context, requestBuilder, cancellationToken);

src/HotChocolate/AspNetCore/src/AspNetCore.Pipeline/Parsers/DefaultHttpRequestParser.cs

@@ -228,11 +228,7 @@ public GraphQLRequest ParseRequestFromParams(IQueryCollection parameters)
                 extensions = JsonDocument.Parse(se);
             }
 
-            ErrorHandlingMode? errorHandlingMode = null;
-            if (!string.IsNullOrEmpty(onError))
-            {
-                errorHandlingMode = ParseErrorHandlingMode(onError);
-            }
+            var errorHandlingMode = ParseErrorHandlingMode(onError);
 
             return new GraphQLRequest(
                 document,
@@ -327,8 +323,13 @@ public GraphQLRequest ParsePersistedOperationRequestFromParams(
         return (documentHash, document);
     }
 
-    private static ErrorHandlingMode? ParseErrorHandlingMode(string onError)
+    private static ErrorHandlingMode? ParseErrorHandlingMode(string? onError)
     {
+        if (string.IsNullOrEmpty(onError))
+        {
+            return null;
+        }
+
         if (onError.Equals("PROPAGATE", StringComparison.OrdinalIgnoreCase))
         {
             return ErrorHandlingMode.Propagate;
@@ -339,12 +340,8 @@ public GraphQLRequest ParsePersistedOperationRequestFromParams(
             return ErrorHandlingMode.Null;
         }
 
-        if (onError.Equals("HALT", StringComparison.OrdinalIgnoreCase))
-        {
-            return ErrorHandlingMode.Halt;
-        }
-
-        return null;
+        throw new InvalidGraphQLRequestException(
+            $"Unknown 'onError' value '{onError}'. Allowed values are 'PROPAGATE' or 'NULL'.");
     }
 
     public GraphQLRequest[] ParseRequest(string sourceText)

src/HotChocolate/AspNetCore/src/Transport.Abstractions/Serialization/Utf8JsonWriterHelper.cs

@@ -728,7 +728,6 @@ private static string GetErrorHandlingModeAsString(ErrorHandlingMode mode)
         {
             ErrorHandlingMode.Propagate => "PROPAGATE",
             ErrorHandlingMode.Null => "NULL",
-            ErrorHandlingMode.Halt => "HALT",
             _ => throw new ArgumentOutOfRangeException(nameof(mode))
         };
     }

src/HotChocolate/AspNetCore/src/Transport.Http/DefaultGraphQLHttpClient.cs

@@ -599,7 +599,6 @@ private static string GetErrorHandlingModeAsString(ErrorHandlingMode mode)
         {
             ErrorHandlingMode.Propagate => "PROPAGATE",
             ErrorHandlingMode.Null => "NULL",
-            ErrorHandlingMode.Halt => "HALT",
             _ => throw new ArgumentOutOfRangeException(nameof(mode))
         };
     }

src/HotChocolate/AspNetCore/test/AspNetCore.Tests/GraphQLOverHttpSpecTests.cs

@@ -540,6 +540,27 @@ public async Task After_Execution_StatusCode_Is_200()
         Assert.Equal(OK, response.StatusCode);
     }
 
+    [Fact]
+    public async Task Unknown_OnError_Value_Returns_BadRequest()
+    {
+        // arrange
+        var client = GetClient(Latest);
+
+        // act
+        using var request = new HttpRequestMessage(HttpMethod.Post, s_url);
+        request.Content = new StringContent(
+            """{"query":"{ __typename }","onError":"HALT"}""",
+            System.Text.Encoding.UTF8,
+            "application/json");
+
+        using var response = await client.SendAsync(request);
+
+        // assert
+        Assert.Equal(BadRequest, response.StatusCode);
+        var body = await response.Content.ReadAsStringAsync();
+        Assert.Contains("onError", body, StringComparison.OrdinalIgnoreCase);
+    }
+
     private HttpClient GetClient(HttpTransportVersion serverTransportVersion)
     {
         var server = CreateStarWarsServer(

src/HotChocolate/AspNetCore/test/Transport.Http.Tests/GraphQLHttpClientTests.cs

@@ -442,7 +442,7 @@ public async Task Post_GraphQL_Query_With_OnError()
 
         // act
         var response = await client.PostAsync(
-            new OperationRequest(query, onError: ErrorHandlingMode.Halt),
+            new OperationRequest(query, onError: ErrorHandlingMode.Null),
             cts.Token);
 
         // assert
@@ -451,7 +451,7 @@ public async Task Post_GraphQL_Query_With_OnError()
             """
             {
               "data": {
-                "errorHandlingMode": "HALT"
+                "errorHandlingMode": "NULL"
               }
             }
             """);
@@ -766,7 +766,7 @@ public async Task Get_GraphQL_Query_With_OnError()
 
         // act
         var response = await client.GetAsync(
-            new OperationRequest(query, onError: ErrorHandlingMode.Halt),
+            new OperationRequest(query, onError: ErrorHandlingMode.Null),
             cts.Token);
 
         // assert
@@ -775,7 +775,7 @@ public async Task Get_GraphQL_Query_With_OnError()
             """
             {
               "data": {
-                "errorHandlingMode": "HALT"
+                "errorHandlingMode": "NULL"
               }
             }
             """);

src/HotChocolate/Core/src/Types/Execution/Processing/OperationContext.Pooling.cs

@@ -39,6 +39,7 @@ internal sealed partial class OperationContext
     private int _branchId;
     private int _variableIndex;
     private object? _rootValue;
+    private bool _propagateNullValues;
     private bool _isInitialized;
 
     public OperationContext(
@@ -87,6 +88,10 @@ public void Initialize(
         _batchDispatcher = batchDispatcher;
         _variableIndex = variableIndex;
 
+        var errorHandlingMode = _requestContext.Request.ErrorHandlingMode
+            ?? _schema.GetOptions().DefaultErrorHandlingMode;
+        _propagateNullValues = errorHandlingMode is Language.ErrorHandlingMode.Propagate;
+
         IncludeFlags = operation.CreateIncludeFlags(variables);
         DeferFlags = operation.CreateDeferFlags(variables);
         Result.Data = new ResultDocument(operation, IncludeFlags);
@@ -128,6 +133,7 @@ public void InitializeDeferContext(
         _currentBranchTracker = context._currentBranchTracker;
         _currentWorkScheduler = context._currentWorkScheduler;
         _currentDeferExecutionCoordinator = context._currentDeferExecutionCoordinator;
+        _propagateNullValues = context._propagateNullValues;
         _branchId = executionBranchId;
         _isInitialized = true;
 
@@ -178,6 +184,7 @@ public void Clean()
             _resolveQueryRootValue = null!;
             _batchDispatcher = null!;
             _branchId = int.MinValue;
+            _propagateNullValues = false;
             _isInitialized = false;
             Result.Reset();
         }

src/HotChocolate/Core/src/Types/Execution/Processing/OperationContext.cs

@@ -29,6 +29,12 @@ public CancellationToken RequestAborted
         }
     }
 
+    /// <summary>
+    /// Gets whether null values should be propagated to nullable parents
+    /// (standard GraphQL behavior). When false, null stays at the field that caused it.
+    /// </summary>
+    public bool PropagateNullValues => _propagateNullValues;
+
     /// <inheritdoc />
     public IFeatureCollection Features
     {

src/HotChocolate/Core/src/Types/Execution/Processing/Tasks/BatchResolverTask.cs

@@ -377,7 +377,15 @@ private void CompleteValues(
 
             if (resultValue is { IsNullable: false, IsNullOrInvalidated: true })
             {
-                PropagateNullValues(resultValue);
+                if (_operationContext.PropagateNullValues)
+                {
+                    PropagateNullValues(resultValue);
+                }
+                else
+                {
+                    resultValue.SetNullValue();
+                }
+
                 _completionStatus = ExecutionTaskStatus.Faulted;
                 _operationContext.Result.AddNonNullViolation(context.Path);
                 _taskBuffer.Clear();

src/HotChocolate/Core/src/Types/Execution/Processing/Tasks/ResolverTask.CompleteValue.cs

@@ -44,7 +44,15 @@ private void CompleteValue(bool success, CancellationToken cancellationToken)
 
         if (resultValue is { IsNullable: false, IsNullOrInvalidated: true })
         {
-            PropagateNullValues(resultValue);
+            if (_operationContext.PropagateNullValues)
+            {
+                PropagateNullValues(resultValue);
+            }
+            else
+            {
+                resultValue.SetNullValue();
+            }
+
             _completionStatus = ExecutionTaskStatus.Faulted;
             _operationContext.Result.AddNonNullViolation(_context.Path);
             _taskBuffer.Clear();

src/HotChocolate/Core/src/Types/Execution/Processing/Tasks/ResolverTaskFactory.cs

@@ -349,7 +349,15 @@ private static void ResolveAndCompleteInline(
 
         if (fieldValue is { IsNullable: false, IsNullOrInvalidated: true })
         {
-            PropagateNullValues(fieldValue);
+            if (operationContext.PropagateNullValues)
+            {
+                PropagateNullValues(fieldValue);
+            }
+            else
+            {
+                fieldValue.SetNullValue();
+            }
+
             operationContext.Result.AddNonNullViolation(fieldValue.Path);
         }
     }

src/HotChocolate/Core/src/Types/IReadOnlySchemaOptions.cs

@@ -1,6 +1,7 @@
 using System.Reflection;
 using HotChocolate.Configuration;
 using HotChocolate.Execution;
+using HotChocolate.Language;
 using HotChocolate.Types;
 
 namespace HotChocolate;
@@ -230,4 +231,9 @@ public interface IReadOnlySchemaOptions
     /// Applies the @serializeAs directive to scalar types that specify a serialization format.
     /// </summary>
     bool ApplySerializeAsToScalars { get; }
+
+    /// <summary>
+    /// Gets the default error handling mode for null propagation.
+    /// </summary>
+    ErrorHandlingMode DefaultErrorHandlingMode { get; }
 }

src/HotChocolate/Core/src/Types/SchemaOptions.cs

@@ -1,6 +1,7 @@
 using System.Reflection;
 using HotChocolate.Configuration;
 using HotChocolate.Execution;
+using HotChocolate.Language;
 using HotChocolate.Types;
 
 namespace HotChocolate;
@@ -189,6 +190,9 @@ public int OperationDocumentCacheSize
     /// <inheritdoc cref="IReadOnlySchemaOptions.ApplySerializeAsToScalars"/>
     public bool ApplySerializeAsToScalars { get; set; }
 
+    /// <inheritdoc cref="IReadOnlySchemaOptions.DefaultErrorHandlingMode"/>
+    public ErrorHandlingMode DefaultErrorHandlingMode { get; set; } = ErrorHandlingMode.Propagate;
+
     /// <summary>
     /// Creates a mutable options object from a read-only options object.
     /// </summary>
@@ -230,6 +234,7 @@ public static SchemaOptions FromOptions(IReadOnlySchemaOptions options)
             ApplyShareableToPageInfo = options.ApplyShareableToPageInfo,
             ApplyShareableToConnections = options.ApplyShareableToConnections,
             ApplyShareableToNodeFields = options.ApplyShareableToNodeFields,
-            ApplySerializeAsToScalars = options.ApplySerializeAsToScalars
+            ApplySerializeAsToScalars = options.ApplySerializeAsToScalars,
+            DefaultErrorHandlingMode = options.DefaultErrorHandlingMode
         };
 }

src/HotChocolate/Core/test/Execution.Abstractions.Tests/Execution/OperationRequestBuilderTests.cs

@@ -315,7 +315,7 @@ public void BuildRequest_SetErrorHandlingMode()
         var request =
             OperationRequestBuilder.New()
                 .SetDocument("{ foo }")
-                .SetErrorHandlingMode(ErrorHandlingMode.Halt)
+                .SetErrorHandlingMode(ErrorHandlingMode.Null)
                 .Build();
 
         // assert
@@ -330,7 +330,7 @@ public void BuildRequest_SetErrorHandlingMode_VariableBatchRequest()
         var request =
             OperationRequestBuilder.New()
                 .SetDocument("{ foo }")
-                .SetErrorHandlingMode(ErrorHandlingMode.Halt)
+                .SetErrorHandlingMode(ErrorHandlingMode.Null)
                 .SetVariableValues([new Dictionary<string, object?> { ["one"] = "foo" }])
                 .Build();
 

src/HotChocolate/Core/test/Execution.Abstractions.Tests/Execution/__snapshots__/OperationRequestBuilderTests.BuildRequest_SetErrorHandlingMode.snap

@@ -1,4 +1,4 @@
 {
   "document": "{ foo }",
-  "errorHandlingMode": "Halt"
+  "errorHandlingMode": "Null"
 }

src/HotChocolate/Core/test/Execution.Abstractions.Tests/Execution/__snapshots__/OperationRequestBuilderTests.BuildRequest_SetErrorHandlingMode_VariableBatchRequest.snap

@@ -1,6 +1,6 @@
 {
   "document": "{ foo }",
-  "errorHandlingMode": "Halt",
+  "errorHandlingMode": "Null",
   "variableValues": [
     {
       "one": "foo"