Added support for AggregateError to the execution pipeline. (#4014)

src/HotChocolate/Core/src/Abstractions/AggregateError.cs

@@ -0,0 +1,29 @@
+using System.Collections.Generic;
+using System.Linq;
+using HotChocolate.Properties;
+
+namespace HotChocolate
+{
+    /// <summary>
+    /// An aggregate error allows to pass a collection of error in a single error object.
+    /// </summary>
+    public class AggregateError : Error
+    {
+        public AggregateError(IEnumerable<IError> errors)
+            : base(AbstractionResources.AggregateError_Message)
+        {
+            Errors = errors.ToArray();
+        }
+
+        public AggregateError(params IError[] errors)
+            : base(AbstractionResources.AggregateError_Message)
+        {
+            Errors = errors.ToArray();
+        }
+
+        /// <summary>
+        /// Gets the actual errors.
+        /// </summary>
+        public IReadOnlyList<IError> Errors { get; }
+    }
+}

src/HotChocolate/Core/src/Abstractions/Error.cs

@@ -8,10 +8,16 @@
 
 namespace HotChocolate
 {
-    public sealed class Error : IError
+    /// <summary>
+    /// Represents a GraphQL execution error.
+    /// </summary>
+    public class Error : IError
     {
         private const string _codePropertyName = "code";
 
+        /// <summary>
+        /// Initializes a new instance of <see cref="Error"/>.
+        /// </summary>
         public Error(
             string message,
             string? code = null,
@@ -77,8 +83,8 @@ public IError WithCode(string? code)
                 return RemoveCode();
             }
 
-            var extensions = Extensions is null
-                ? new OrderedDictionary<string, object?>() { [_codePropertyName] = code }
+            OrderedDictionary<string, object?> extensions = Extensions is null
+                ? new OrderedDictionary<string, object?> { [_codePropertyName] = code }
                 : new OrderedDictionary<string, object?>(Extensions) { [_codePropertyName] = code };
             return new Error(Message, code, Path, Locations, extensions, Exception);
         }
@@ -157,7 +163,7 @@ public IError SetExtension(string key, object? value)
                     nameof(key));
             }
 
-            var extensions = Extensions is { }
+            OrderedDictionary<string, object?> extensions = Extensions is { }
                 ? new OrderedDictionary<string, object?>(Extensions)
                 : new OrderedDictionary<string, object?>();
             extensions[key] = value;

src/HotChocolate/Core/src/Abstractions/ErrorHandlerExtensions.cs

@@ -20,16 +20,38 @@ public static IReadOnlyList<IError> Handle(
                 throw new ArgumentNullException(nameof(errors));
             }
 
-            return HandleEnumerator(errorHandler, errors).ToList();
-        }
+            var result = new List<IError>();
 
-        private static IEnumerable<IError> HandleEnumerator(
-            IErrorHandler errorHandler,
-            IEnumerable<IError> errors)
-        {
             foreach (IError error in errors)
             {
-                yield return errorHandler.Handle(error);
+                if (error is AggregateError aggregateError)
+                {
+                    foreach (var innerError in aggregateError.Errors)
+                    {
+                        AddProcessed(errorHandler.Handle(innerError));
+                    }
+                }
+                else
+                {
+                    AddProcessed(errorHandler.Handle(error));
+                }
+            }
+
+            return result;
+
+            void AddProcessed(IError error)
+            {
+                if (error is AggregateError aggregateError)
+                {
+                    foreach (var innerError in aggregateError.Errors)
+                    {
+                        result.Add(innerError);
+                    }
+                }
+                else
+                {
+                    result.Add(error);
+                }
             }
         }
     }

src/HotChocolate/Core/src/Abstractions/Execution/QueryResultBuilder.cs

@@ -32,11 +32,7 @@ public IQueryResultBuilder AddError(IError error)
                 throw new ArgumentNullException(nameof(error));
             }
 
-            if (_errors is null)
-            {
-                _errors = new List<IError>();
-            }
-
+            _errors ??= new List<IError>();
             _errors.Add(error);
             return this;
         }
@@ -48,11 +44,7 @@ public IQueryResultBuilder AddErrors(IEnumerable<IError> errors)
                 throw new ArgumentNullException(nameof(errors));
             }
 
-            if (_errors is null)
-            {
-                _errors = new List<IError>();
-            }
-
+            _errors ??= new List<IError>();
             _errors.AddRange(errors);
             return this;
         }
@@ -65,22 +57,14 @@ public IQueryResultBuilder ClearErrors()
 
         public IQueryResultBuilder AddExtension(string key, object? data)
         {
-            if (_extensionData is null)
-            {
-                _extensionData = new ExtensionData();
-            }
-
+            _extensionData ??= new ExtensionData();
             _extensionData.Add(key, data);
             return this;
         }
 
         public IQueryResultBuilder SetExtension(string key, object? data)
         {
-            if (_extensionData is null)
-            {
-                _extensionData = new ExtensionData();
-            }
-
+            _extensionData ??= new ExtensionData();
             _extensionData[key] = data;
             return this;
         }
@@ -109,22 +93,14 @@ public IQueryResultBuilder ClearExtensions()
 
         public IQueryResultBuilder AddContextData(string key, object? data)
         {
-            if (_contextData is null)
-            {
-                _contextData = new ExtensionData();
-            }
-
+            _contextData ??= new ExtensionData();
             _contextData.Add(key, data);
             return this;
         }
 
         public IQueryResultBuilder SetContextData(string key, object? data)
         {
-            if (_contextData is null)
-            {
-                _contextData = new ExtensionData();
-            }
-
+            _contextData ??= new ExtensionData();
             _contextData[key] = data;
             return this;
         }
@@ -157,23 +133,22 @@ public IQueryResult Create()
         {
             return new QueryResult(
                 _data,
-                _errors is { } && _errors.Count > 0 ? _errors : null,
-                _extensionData is { } && _extensionData.Count > 0 ? _extensionData : null,
-                _contextData is { } && _contextData.Count > 0 ? _contextData : null,
+                _errors is { Count: > 0 } ? _errors : null,
+                _extensionData is { Count: > 0 } ? _extensionData : null,
+                _contextData is { Count: > 0 } ? _contextData : null,
                 _label,
                 _path,
                 _hasNext,
                 _disposable);
         }
 
-        public static QueryResultBuilder New() => new QueryResultBuilder();
+        public static QueryResultBuilder New() => new();
 
         public static QueryResultBuilder FromResult(IQueryResult result)
         {
-            var builder = new QueryResultBuilder();
-            builder._data = result.Data;
+            var builder = new QueryResultBuilder { _data = result.Data };
 
-            if (result.Errors is { })
+            if (result.Errors is not null)
             {
                 builder._errors = new List<IError>(result.Errors);
             }
@@ -182,7 +157,7 @@ public static QueryResultBuilder FromResult(IQueryResult result)
             {
                 builder._extensionData = new ExtensionData(d);
             }
-            else if (result.Extensions is { })
+            else if (result.Extensions is not null)
             {
                 builder._extensionData = new ExtensionData(result.Extensions);
             }
@@ -192,12 +167,15 @@ public static QueryResultBuilder FromResult(IQueryResult result)
 
         public static IQueryResult CreateError(
             IError error,
-            IReadOnlyDictionary<string, object?>? contextData = null) =>
-            new QueryResult(null, new List<IError> { error }, contextData: contextData);
+            IReadOnlyDictionary<string, object?>? contextData = null)
+            => error is AggregateError aggregateError
+                ? CreateError(aggregateError.Errors, contextData)
+                : new QueryResult(null, new List<IError> { error }, contextData: contextData);
+
 
         public static IQueryResult CreateError(
             IReadOnlyList<IError> errors,
-            IReadOnlyDictionary<string, object?>? contextData = null) =>
-            new QueryResult(null, errors, contextData: contextData);
+            IReadOnlyDictionary<string, object?>? contextData = null)
+            => new QueryResult(null, errors, contextData: contextData);
     }
 }

src/HotChocolate/Core/src/Abstractions/IError.cs

@@ -6,7 +6,7 @@
 namespace HotChocolate
 {
     /// <summary>
-    /// Represents a schema or query error.
+    /// Represents a GraphQL execution error.
     /// </summary>
     public interface IError
     {

src/HotChocolate/Core/src/Abstractions/Properties/AbstractionResources.resx

@@ -186,4 +186,7 @@
   <data name="FieldCoordinate_Parse_InvalidFormat" xml:space="preserve">
     <value>The string has an invalid format.</value>
   </data>
+  <data name="AggregateError_Message" xml:space="preserve">
+    <value>For error details look at the `Errors` property.</value>
+  </data>
 </root>

src/HotChocolate/Core/src/Execution/DependencyInjection/SchemaRequestExecutorBuilderExtensions.Resolvers.cs

@@ -10,24 +10,6 @@ namespace Microsoft.Extensions.DependencyInjection
 {
     public static partial class SchemaRequestExecutorBuilderExtensions
     {
-        public static IRequestExecutorBuilder AddResolver(
-            this IRequestExecutorBuilder builder,
-            FieldResolver fieldResolver)
-        {
-            if (builder is null)
-            {
-                throw new ArgumentNullException(nameof(builder));
-            }
-
-            if (fieldResolver is null)
-            {
-                throw new ArgumentNullException(nameof(fieldResolver));
-            }
-
-            // return builder.ConfigureSchema(b => b.AddResolver(fieldResolver));
-            throw new NotImplementedException();
-        }
-
         /// <summary>
         /// Adds a resolver delegate for a specific field.
         /// </summary>

src/HotChocolate/Core/src/Execution/Processing/MiddlewareContext.Global.cs

@@ -140,10 +140,40 @@ public void ReportError(IError error)
                 throw new ArgumentNullException(nameof(error));
             }
 
-            error = _operationContext.ErrorHandler.Handle(error);
-            _operationContext.Result.AddError(error, _selection.SyntaxNode);
-            _operationContext.DiagnosticEvents.ResolverError(this, error);
-            HasErrors = true;
+            if (error is AggregateError aggregateError)
+            {
+                foreach (var innerError in aggregateError.Errors)
+                {
+                    ReportSingle(innerError);
+                }
+            }
+            else
+            {
+                ReportSingle(error);
+            }
+
+            void ReportSingle(IError singleError)
+            {
+                AddProcessedError(_operationContext.ErrorHandler.Handle(singleError));
+                HasErrors = true;
+            }
+
+            void AddProcessedError(IError processed)
+            {
+                if (processed is AggregateError ar)
+                {
+                    foreach (var ie in ar.Errors)
+                    {
+                        _operationContext.Result.AddError(ie, _selection.SyntaxNode);
+                        _operationContext.DiagnosticEvents.ResolverError(this, ie);
+                    }
+                }
+                else
+                {
+                    _operationContext.Result.AddError(processed, _selection.SyntaxNode);
+                    _operationContext.DiagnosticEvents.ResolverError(this, processed);
+                }
+            }
         }
 
         public async ValueTask<T> ResolveAsync<T>()

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

@@ -32,9 +32,40 @@ private void ReportError(IExecutionTask task, IError error)
             }
 
             AssertInitialized();
-            error = ErrorHandler.Handle(error);
-            Result.AddError(error);
-            DiagnosticEvents.TaskError(task, error);
+
+            if (error is AggregateError aggregateError)
+            {
+                foreach (var innerError in aggregateError.Errors)
+                {
+                    ReportSingle(innerError);
+                }
+            }
+            else
+            {
+                ReportSingle(error);
+            }
+
+            void ReportSingle(IError singleError)
+            {
+                AddProcessedError(ErrorHandler.Handle(singleError));
+            }
+
+            void AddProcessedError(IError processed)
+            {
+                if (processed is AggregateError ar)
+                {
+                    foreach (var ie in ar.Errors)
+                    {
+                        Result.AddError(ie);
+                        DiagnosticEvents.TaskError(task, ie);
+                    }
+                }
+                else
+                {
+                    Result.AddError(processed);
+                    DiagnosticEvents.TaskError(task, processed);
+                }
+            }
         }
 
         void IExecutionTaskContext.Completed(IExecutionTask task)