[Fusion] RawOperationResult.Errors should be null if there are no errors (#8839)

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

Author: tobias-tengler

src/HotChocolate/AspNetCore/benchmarks/k6/performance-data.json

@@ -1,20 +1,20 @@
 {
-  "timestamp": "2025-10-23T10:04:55Z",
+  "timestamp": "2025-10-23T08:31:24Z",
   "tests": {
     "single-fetch": {
       "name": "Single Fetch (50 products, names only)",
       "response_time": {
-        "min": 1.354974,
-        "p50": 1.917465,
-        "max": 39.045215,
-        "avg": 2.211277226896645,
-        "p90": 3.051409,
-        "p95": 3.6816645,
-        "p99": 6.286266199999994
+        "min": 1.360442,
+        "p50": 1.74927,
+        "max": 41.901381,
+        "avg": 1.9882560501470818,
+        "p90": 2.582531,
+        "p95": 3.056496999999996,
+        "p99": 5.826263539999997
       },
       "throughput": {
-        "requests_per_second": 78.77656643800736,
-        "total_iterations": 7162
+        "requests_per_second": 78.79703615241581,
+        "total_iterations": 7170
       },
       "reliability": {
         "error_rate": 0
@@ -23,17 +23,17 @@
     "dataloader": {
       "name": "DataLoader (50 products with brands)",
       "response_time": {
-        "min": 2.690869,
-        "p50": 4.002113,
-        "max": 19.431387,
-        "avg": 4.3774701576950115,
-        "p90": 5.953583,
-        "p95": 7.3601592999999905,
-        "p99": 10.701773639999999
+        "min": 2.629259,
+        "p50": 3.337894,
+        "max": 16.534475,
+        "avg": 3.700613336003375,
+        "p90": 4.795968,
+        "p95": 5.8992587499999996,
+        "p99": 9.208675050000002
       },
       "throughput": {
-        "requests_per_second": 78.52895150550104,
-        "total_iterations": 7146
+        "requests_per_second": 78.60019900711032,
+        "total_iterations": 7147
       },
       "reliability": {
         "error_rate": 0

src/HotChocolate/Fusion-vnext/src/Fusion.Execution/Execution/OperationPlanContext.cs

@@ -287,6 +287,7 @@ internal IOperationResult Complete()
             var writer = new PooledArrayWriter();
             s_planFormatter.Format(writer, OperationPlan, trace);
             var value = new RawJsonValue(writer.WrittenMemory);
+            result.Extensions ??= [];
             result.Extensions.Add("fusion", new Dictionary<string, object?> { { "operationPlan", value } });
             operationResult.RegisterForCleanup(writer);
         }
@@ -298,7 +299,7 @@ internal IOperationResult Complete()
 
         Debug.Assert(
             !result.Data.IsInvalidated
-                || (result.Errors.Count > 0),
+                || result.Errors?.Count > 0,
             "Expected to either valid data or errors");
 
         _clientScope = RequestContext.CreateClientScope();

src/HotChocolate/Fusion-vnext/src/Fusion.Execution/Execution/Pipeline/FusionMiddleware.cs

@@ -7,33 +7,18 @@ namespace HotChocolate.Fusion.Execution.Pipeline;
 /// </summary>
 public static class FusionMiddleware
 {
-    public static string OperationExecutionKey
-        => nameof(OperationExecutionMiddleware);
-
     public static RequestMiddlewareConfiguration OperationExecution
         => OperationExecutionMiddleware.Create();
 
-    public static string OperationPlanCacheKey
-        => nameof(OperationPlanCacheMiddleware);
-
     public static RequestMiddlewareConfiguration OperationPlanCache
         => OperationPlanCacheMiddleware.Create();
 
-    public static string OperationPlanKey
-        => nameof(OperationPlanMiddleware);
-
     public static RequestMiddlewareConfiguration OperationPlan
         => OperationPlanMiddleware.Create();
 
-    public static string OperationVariableCoercionKey
-        => nameof(OperationVariableCoercionMiddleware);
-
     public static RequestMiddlewareConfiguration OperationVariableCoercion
         => OperationVariableCoercionMiddleware.Create();
 
-    public static string TimeoutKey
-        => nameof(TimeoutMiddleware);
-
     public static RequestMiddlewareConfiguration Timeout
         => TimeoutMiddleware.Create();
 }

src/HotChocolate/Fusion-vnext/src/Fusion.Execution/Execution/Results/FetchResultStore.cs

@@ -107,6 +107,7 @@ public bool AddPartialResults(
 
                 if (result.Errors?.RootErrors is { Length: > 0 } rootErrors)
                 {
+                    _result.Errors ??= [];
                     _result.Errors.AddRange(rootErrors);
                 }
 

src/HotChocolate/Fusion-vnext/src/Fusion.Execution/Execution/Results/ValueCompletion.cs

@@ -115,6 +115,7 @@ public bool BuildErrorResult(
                 .Build();
             errorWithPath = _errorHandler.Handle(errorWithPath);
 
+            _result.Errors ??= [];
             _result.Errors.Add(errorWithPath);
 
             switch (_errorHandlingMode)
@@ -191,6 +192,8 @@ private bool TryCompleteValue(
                 }
 
                 error = _errorHandler.Handle(error);
+
+                _result.Errors ??= [];
                 _result.Errors.Add(error);
 
                 if (_errorHandlingMode is ErrorHandlingMode.Propagate or ErrorHandlingMode.Halt)
@@ -217,6 +220,8 @@ private bool TryCompleteValue(
                     .AddLocation(selection.SyntaxNodes[0].Node)
                     .Build();
                 errorWithPath = _errorHandler.Handle(errorWithPath);
+
+                _result.Errors ??= [];
                 _result.Errors.Add(errorWithPath);
 
                 if (_errorHandlingMode is ErrorHandlingMode.Halt)
@@ -282,6 +287,8 @@ private bool TryCompleteList(
                     .AddLocation(selection.SyntaxNodes[0].Node)
                     .Build();
                 errorWithPath = _errorHandler.Handle(errorWithPath);
+
+                _result.Errors ??= [];
                 _result.Errors.Add(errorWithPath);
 
                 if (_errorHandlingMode is ErrorHandlingMode.Halt)

src/HotChocolate/Fusion-vnext/src/Fusion.Execution/Text/Json/CompositeResultDocument.cs

@@ -28,22 +28,16 @@ public CompositeResultDocument(Operation operation, ulong includeFlags)
 
     public CompositeResultElement Data { get; }
 
-    public List<IError> Errors
+    public List<IError>? Errors
     {
-        get
-        {
-            _errors ??= [];
-            return _errors;
-        }
+        get => _errors;
+        internal set => _errors = value;
     }
 
-    public Dictionary<string, object?> Extensions
+    public Dictionary<string, object?>? Extensions
     {
-        get
-        {
-            _extensions ??= [];
-            return _extensions;
-        }
+        get => _extensions;
+        internal set => _extensions = value;
     }
 
     [MethodImpl(MethodImplOptions.AggressiveInlining)]