[Experimental] Adds True Nullability GraphQL Spec Proposal (#6570)

src/HotChocolate/Core/src/Abstractions/WellKnownContextData.cs

@@ -274,4 +274,9 @@ public static class WellKnownContextData
     /// The key to access the authorization allowed flag on the member context.
     /// </summary>
     public const string AllowAnonymous = "HotChocolate.Authorization.AllowAnonymous";
+
+    /// <summary>
+    /// The key to access the true nullability flag on the execution context.
+    /// </summary>
+    public const string EnableTrueNullability = "HotChocolate.Types.EnableTrueNullability";
 }

src/HotChocolate/Core/src/Abstractions/WellKnownDirectives.cs

@@ -69,4 +69,8 @@ public static class WellKnownDirectives
     /// The name of the @tag argument name.
     /// </summary>
     public const string Name = "name";
+
+    public const string NullBubbling = "nullBubbling";
+
+    public const string Enable = "enable";
 }

src/HotChocolate/Core/src/Execution/ErrorHelper.cs

@@ -249,4 +249,22 @@ public static IError ReadPersistedQueryMiddleware_PersistedQueryNotFound()
             .SetMessage("PersistedQueryNotFound")
             .SetCode(ErrorCodes.Execution.PersistedQueryNotFound)
             .Build();
+
+    public static IError NoNullBubbling_ArgumentValue_NotAllowed(
+        ArgumentNode argument)
+    {
+        var errorBuilder = ErrorBuilder.New();
+
+        if (argument.Value.Location is not null)
+        {
+            errorBuilder.AddLocation(
+                argument.Value.Location.Line,
+                argument.Value.Location.Column);
+        }
+
+        errorBuilder.SetSyntaxNode(argument.Value);
+        errorBuilder.SetMessage(ErrorHelper_NoNullBubbling_ArgumentValue_NotAllowed);
+
+        return errorBuilder.Build();
+    }
 }

src/HotChocolate/Core/src/Execution/Pipeline/OperationResolverMiddleware.cs

@@ -5,28 +5,39 @@
 using HotChocolate.Execution.Processing;
 using HotChocolate.Language;
 using HotChocolate.Types;
+using HotChocolate.Utilities;
 using Microsoft.Extensions.ObjectPool;
+using static HotChocolate.Execution.ErrorHelper;
+using static HotChocolate.WellKnownDirectives;
+using static HotChocolate.Execution.Pipeline.PipelineTools;
+using static HotChocolate.WellKnownContextData;
 
 namespace HotChocolate.Execution.Pipeline;
 
 internal sealed class OperationResolverMiddleware
 {
     private readonly RequestDelegate _next;
     private readonly ObjectPool<OperationCompiler> _operationCompilerPool;
+    private readonly VariableCoercionHelper _coercionHelper;
     private readonly IReadOnlyList<IOperationCompilerOptimizer>? _optimizers;
 
     public OperationResolverMiddleware(
         RequestDelegate next,
         ObjectPool<OperationCompiler> operationCompilerPool,
-        IEnumerable<IOperationCompilerOptimizer> optimizers)
+        IEnumerable<IOperationCompilerOptimizer> optimizers,
+        VariableCoercionHelper coercionHelper)
     {
         if (optimizers is null)
         {
             throw new ArgumentNullException(nameof(optimizers));
         }
 
-        _next = next ?? throw new ArgumentNullException(nameof(next));
-        _operationCompilerPool = operationCompilerPool;
+        _next = next ?? 
+            throw new ArgumentNullException(nameof(next));
+        _operationCompilerPool = operationCompilerPool ?? 
+            throw new ArgumentNullException(nameof(operationCompilerPool));
+        _coercionHelper = coercionHelper ?? 
+            throw new ArgumentNullException(nameof(coercionHelper));
         _optimizers = optimizers.ToArray();
     }
 
@@ -45,7 +56,7 @@ public async ValueTask InvokeAsync(IRequestContext context)
 
                 if (operationType is null)
                 {
-                    context.Result = ErrorHelper.RootTypeNotFound(operationDef.Operation);
+                    context.Result = RootTypeNotFound(operationDef.Operation);
                     return;
                 }
 
@@ -61,7 +72,7 @@ public async ValueTask InvokeAsync(IRequestContext context)
         }
         else
         {
-            context.Result = ErrorHelper.StateInvalidForOperationResolver();
+            context.Result = StateInvalidForOperationResolver();
         }
     }
 
@@ -78,7 +89,8 @@ private IOperation CompileOperation(
             operationType,
             context.Document!,
             context.Schema,
-            _optimizers);
+            _optimizers,
+            IsNullBubblingEnabled(context, operationDefinition));
         _operationCompilerPool.Return(compiler);
         return operation;
     }
@@ -93,4 +105,60 @@ private IOperation CompileOperation(
             OperationType.Subscription => schema.SubscriptionType,
             _ => throw ThrowHelper.RootTypeNotSupported(operationType)
         };
-}
+
+    private bool IsNullBubblingEnabled(IRequestContext context, OperationDefinitionNode operationDefinition)
+    {
+        if (!context.Schema.ContextData.ContainsKey(EnableTrueNullability) ||
+            operationDefinition.Directives.Count == 0)
+        {
+            return true;
+        }
+
+        var enabled = true;
+
+        for (var i = 0; i < operationDefinition.Directives.Count; i++)
+        {
+            var directive = operationDefinition.Directives[i];
+
+            if (!directive.Name.Value.EqualsOrdinal(NullBubbling))
+            {
+                continue;
+            }
+
+            for (var j = 0; j < directive.Arguments.Count; j++)
+            {
+                var argument = directive.Arguments[j];
+
+                if (argument.Name.Value.EqualsOrdinal(Enable))
+                {
+                    if (argument.Value is BooleanValueNode b)
+                    {
+                        enabled = b.Value;
+                        break;
+                    }
+
+                    if (argument.Value is VariableNode v)
+                    {
+                        enabled = CoerceVariable(context, operationDefinition, v);
+                        break;
+                    }
+
+                    throw new GraphQLException(NoNullBubbling_ArgumentValue_NotAllowed(argument));
+                }
+            }
+
+            break;
+        }
+
+        return enabled;
+    }
+
+    private bool CoerceVariable(
+        IRequestContext context, 
+        OperationDefinitionNode operationDefinition, 
+        VariableNode variable)
+    {
+        var variables = CoerceVariables(context, _coercionHelper, operationDefinition.VariableDefinitions);
+        return variables.GetVariable<bool>(variable.Name.Value);
+    } 
+}

src/HotChocolate/Core/src/Execution/Pipeline/PipelineTools.cs

@@ -25,19 +25,20 @@ public static string CreateCacheId(
         string? operationName)
         => CreateCacheId(context, CreateOperationId(documentId, operationName));
 
-    public static void CoerceVariables(
+    public static IVariableValueCollection CoerceVariables(
         IRequestContext context,
         VariableCoercionHelper coercionHelper,
         IReadOnlyList<VariableDefinitionNode> variableDefinitions)
     {
         if (context.Variables is not null)
         {
-            return;
+            return context.Variables;
         }
 
         if (variableDefinitions.Count == 0)
         {
             context.Variables = _noVariables;
+            return _noVariables;
         }
         else
         {
@@ -52,6 +53,7 @@ public static void CoerceVariables(
                     coercedValues);
 
                 context.Variables = new VariableValueCollection(coercedValues);
+                return context.Variables;
             }
         }
     }

src/HotChocolate/Core/src/Execution/Processing/OperationCompiler.CompilerContext.cs

@@ -8,17 +8,11 @@ namespace HotChocolate.Execution.Processing;
 
 public sealed partial class OperationCompiler
 {
-    internal sealed class CompilerContext
+    internal sealed class CompilerContext(ISchema schema, DocumentNode document, bool disableNullBubbling)
     {
-        public CompilerContext(ISchema schema, DocumentNode document)
-        {
-            Schema = schema;
-            Document = document;
-        }
-
-        public ISchema Schema { get; }
+        public ISchema Schema { get; } = schema;
 
-        public DocumentNode Document { get; }
+        public DocumentNode Document { get; } = document;
 
         public ObjectType Type { get; private set; } = default!;
 
@@ -35,6 +29,8 @@ public CompilerContext(ISchema schema, DocumentNode document)
 
         public IImmutableList<ISelectionSetOptimizer> Optimizers { get; private set; } =
             ImmutableList<ISelectionSetOptimizer>.Empty;
+
+        public bool EnableNullBubbling { get; } = disableNullBubbling;
 
         public void Initialize(
             ObjectType type,

src/HotChocolate/Core/src/Execution/Processing/OperationCompiler.cs

@@ -24,6 +24,7 @@ public sealed partial class OperationCompiler
 {
     private static readonly ImmutableList<ISelectionSetOptimizer> _emptyOptimizers =
         ImmutableList<ISelectionSetOptimizer>.Empty;
+
     private readonly InputParser _parser;
     private readonly CreateFieldPipeline _createFieldPipeline;
     private readonly Stack<BacklogItem> _backlog = new();
@@ -65,7 +66,8 @@ public IOperation Compile(
         ObjectType operationType,
         DocumentNode document,
         ISchema schema,
-        IReadOnlyList<IOperationCompilerOptimizer>? optimizers = null)
+        IReadOnlyList<IOperationCompilerOptimizer>? optimizers = null,
+        bool enableNullBubbling = true)
     {
         if (string.IsNullOrEmpty(operationId))
         {
@@ -112,7 +114,7 @@ public IOperation Compile(
             var variants = GetOrCreateSelectionVariants(id);
             SelectionSetInfo[] infos = { new(operationDefinition.SelectionSet, 0) };
 
-            var context = new CompilerContext(schema, document);
+            var context = new CompilerContext(schema, document, enableNullBubbling);
             context.Initialize(operationType, variants, infos, rootPath, rootOptimizers);
             CompileSelectionSet(context);
 
@@ -378,19 +380,19 @@ private void CompleteSelectionSet(CompilerContext context)
                 // For now we only allow streams on lists of composite types.
                 if (selection.SyntaxNode.IsStreamable())
                 {
-                     var streamDirective = selection.SyntaxNode.GetStreamDirectiveNode();
-                     var nullValue = NullValueNode.Default;
-                     var ifValue = streamDirective?.GetIfArgumentValueOrDefault() ?? nullValue;
-                     long ifConditionFlags = 0;
-
-                     if (ifValue.Kind is not SyntaxKind.NullValue)
-                     {
-                         var ifCondition = new IncludeCondition(ifValue, nullValue);
-                         ifConditionFlags = GetSelectionIncludeCondition(ifCondition, 0);
-                     }
-
-                     selection.MarkAsStream(ifConditionFlags);
-                     _hasIncrementalParts = true;
+                    var streamDirective = selection.SyntaxNode.GetStreamDirectiveNode();
+                    var nullValue = NullValueNode.Default;
+                    var ifValue = streamDirective?.GetIfArgumentValueOrDefault() ?? nullValue;
+                    long ifConditionFlags = 0;
+
+                    if (ifValue.Kind is not SyntaxKind.NullValue)
+                    {
+                        var ifCondition = new IncludeCondition(ifValue, nullValue);
+                        ifConditionFlags = GetSelectionIncludeCondition(ifCondition, 0);
+                    }
+
+                    selection.MarkAsStream(ifConditionFlags);
+                    _hasIncrementalParts = true;
                 }
             }
 
@@ -449,21 +451,21 @@ private void ResolveFields(
             case SyntaxKind.Field:
                 ResolveField(
                     context,
-                    (FieldNode)selection,
+                    (FieldNode) selection,
                     includeCondition);
                 break;
 
             case SyntaxKind.InlineFragment:
                 ResolveInlineFragment(
                     context,
-                    (InlineFragmentNode)selection,
+                    (InlineFragmentNode) selection,
                     includeCondition);
                 break;
 
             case SyntaxKind.FragmentSpread:
                 ResolveFragmentSpread(
                     context,
-                    (FragmentSpreadNode)selection,
+                    (FragmentSpreadNode) selection,
                     includeCondition);
                 break;
         }
@@ -481,7 +483,9 @@ private void ResolveField(
 
         if (context.Type.Fields.TryGetField(fieldName, out var field))
         {
-            var fieldType = field.Type.RewriteNullability(selection.Required);
+            var fieldType = context.EnableNullBubbling
+                ? field.Type.RewriteNullability(selection.Required)
+                : field.Type.RewriteToNullableType();
 
             if (context.Fields.TryGetValue(responseName, out var preparedSelection))
             {
@@ -516,7 +520,9 @@ selection.SelectionSet is not null
                     responseName: responseName,
                     isParallelExecutable: field.IsParallelExecutable,
                     arguments: CoerceArgumentValues(field, selection, responseName),
-                    includeConditions: includeCondition == 0 ? null : new[] { includeCondition });
+                    includeConditions: includeCondition == 0
+                        ? null
+                        : new[] { includeCondition });
 
                 context.Fields.Add(responseName, preparedSelection);
 
@@ -586,6 +592,7 @@ private void ResolveFragment(
                 var ifValue = deferDirective?.GetIfArgumentValueOrDefault() ?? nullValue;
 
                 long ifConditionFlags = 0;
+
                 if (ifValue.Kind is not SyntaxKind.NullValue)
                 {
                     var ifCondition = new IncludeCondition(ifValue, nullValue);
@@ -637,8 +644,8 @@ private static bool DoesTypeApply(IType typeCondition, IObjectType current)
         => typeCondition.Kind switch
         {
             TypeKind.Object => ReferenceEquals(typeCondition, current),
-            TypeKind.Interface => current.IsImplementing((InterfaceType)typeCondition),
-            TypeKind.Union => ((UnionType)typeCondition).Types.ContainsKey(current.Name),
+            TypeKind.Interface => current.IsImplementing((InterfaceType) typeCondition),
+            TypeKind.Union => ((UnionType) typeCondition).Types.ContainsKey(current.Name),
             _ => false
         };
 
@@ -789,7 +796,7 @@ private CompilerContext RentContext(CompilerContext context)
     {
         if (_deferContext is null)
         {
-            return new CompilerContext(context.Schema, context.Document);
+            return new CompilerContext(context.Schema, context.Document, context.EnableNullBubbling);
         }
 
         var temp = _deferContext;
@@ -862,4 +869,4 @@ public override bool Equals(object? obj)
         public override int GetHashCode()
             => HashCode.Combine(SelectionSet, Path);
     }
-}
+}

src/HotChocolate/Core/src/Execution/Properties/Resources.resx

@@ -333,4 +333,7 @@
   <data name="ComplexityAnalyzerCompiler_Enter_OnlyOperations" xml:space="preserve">
     <value>We only compile operations.</value>
   </data>
+  <data name="ErrorHelper_NoNullBubbling_ArgumentValue_NotAllowed" xml:space="preserve">
+    <value>Only boolean values are allowed to switch null bubbling on or off.</value>
+  </data>
 </root>