Fixed issue when projection on node fields. (#7551)

Author: michaelstaib

src/HotChocolate/Core/src/Execution/Extensions/HotChocolateExecutionSelectionExtensions.cs

@@ -74,6 +74,11 @@ public static Expression<Func<TValue, TValue>> AsSelector<TValue>(
             return GetOrCreateExpression<TValue>(selection, builder);
         }
 
+        if ((flags & FieldFlags.NodesField) == FieldFlags.NodesField)
+        {
+            return GetOrCreateNodeExpression<TValue>(selection);
+        }
+
         return GetOrCreateExpression<TValue>(selection);
     }
 
@@ -93,6 +98,13 @@ private static Expression<Func<TValue, TValue>> GetOrCreateExpression<TValue>(
             static (_, ctx) => ctx.builder.TryCompile<TValue>()!,
             (builder, selection));
 
+    private static Expression<Func<TValue, TValue>> GetOrCreateNodeExpression<TValue>(
+        ISelection selection)
+        => selection.DeclaringOperation.GetOrAddState(
+            CreateNodeExpressionKey<TValue>(selection.Id),
+            static (_, ctx) => ctx._builder.BuildNodeExpression<TValue>(ctx.selection),
+            (_builder, selection));
+
     private static bool TryGetExpression<TValue>(
         ISelection selection,
         [NotNullWhen(true)] out Expression<Func<TValue, TValue>>? expression)
@@ -170,6 +182,30 @@ private static string CreateExpressionKey(int key)
         return Encoding.UTF8.GetString(span.Slice(0, written + keyPrefix.Length));
     }
 
+    private static string CreateNodeExpressionKey<TValue>(int key)
+    {
+        var typeName = typeof(TValue).FullName!;
+        var typeNameLength = Encoding.UTF8.GetMaxByteCount(typeName.Length);
+        var keyPrefix = GetKeyPrefix();
+        var requiredBufferSize = EstimateIntLength(key) + keyPrefix.Length + typeNameLength;
+        byte[]? rented = null;
+        var span =  requiredBufferSize <= 256
+            ? stackalloc byte[requiredBufferSize]
+            : (rented = ArrayPool<byte>.Shared.Rent(requiredBufferSize));
+
+        keyPrefix.CopyTo(span);
+        Utf8Formatter.TryFormat(key, span.Slice(keyPrefix.Length), out var written, 'D');
+        var typeNameWritten = Encoding.UTF8.GetBytes(typeName, span.Slice(written + keyPrefix.Length));
+        var keyString = Encoding.UTF8.GetString(span.Slice(0, written + keyPrefix.Length + typeNameWritten));
+
+        if (rented is not null)
+        {
+            ArrayPool<byte>.Shared.Return(rented);
+        }
+
+        return keyString;
+    }
+
     private static ReadOnlySpan<byte> GetKeyPrefix()
         => "hc-dataloader-expr-"u8;
 

src/HotChocolate/Core/src/Execution/Projections/SelectionExpressionBuilder.cs

@@ -31,6 +31,44 @@ public Expression<Func<TRoot, TRoot>> BuildExpression<TRoot>(ISelection selectio
         return Expression.Lambda<Func<TRoot, TRoot>>(selectionSetExpression, parameter);
     }
 
+    public Expression<Func<TRoot, TRoot>> BuildNodeExpression<TRoot>(ISelection selection)
+    {
+        var rootType = typeof(TRoot);
+        var parameter = Expression.Parameter(rootType, "root");
+        var requirements = selection.DeclaringOperation.Schema.Features.GetRequired<FieldRequirementsMetadata>();
+        var context = new Context(parameter, rootType, requirements);
+        var root = new TypeContainer();
+
+        var entityType = selection.DeclaringOperation.GetPossibleTypes(selection).FirstOrDefault(t => t.RuntimeType == typeof(TRoot));
+
+        if (entityType is null)
+        {
+            throw new InvalidOperationException(
+                $"Unable to resolve the entity type from `{typeof(TRoot).FullName}`.");
+        }
+
+        var typeNode = new TypeNode(entityType.RuntimeType);
+        var selectionSet = selection.DeclaringOperation.GetSelectionSet(selection, entityType);
+        CollectSelections(context, selectionSet, typeNode);
+        root.TryAddNode(typeNode);
+
+        if (typeNode.Nodes.Count == 0)
+        {
+            TryAddAnyLeafField(selection, typeNode);
+        }
+
+        CollectTypes(context, selection, root);
+
+        var selectionSetExpression = BuildTypeSwitchExpression(context, root);
+
+        if (selectionSetExpression is null)
+        {
+            throw new InvalidOperationException("The selection set is empty.");
+        }
+
+        return Expression.Lambda<Func<TRoot, TRoot>>(selectionSetExpression, parameter);
+    }
+
     private void CollectTypes(Context context, ISelection selection, TypeContainer parent)
     {
         var namedType = selection.Type.NamedType();
@@ -49,11 +87,12 @@ private void CollectTypes(Context context, ISelection selection, TypeContainer p
                 CollectSelections(context, possibleSelectionSet, possibleTypeNode);
                 parent.TryAddNode(possibleTypeNode);
 
-                if(possibleTypeNode.Nodes.Count == 0)
+                if (possibleTypeNode.Nodes.Count == 0)
                 {
                     TryAddAnyLeafField(selection, possibleTypeNode);
                 }
             }
+
             return;
         }
 
@@ -63,7 +102,7 @@ private void CollectTypes(Context context, ISelection selection, TypeContainer p
         CollectSelections(context, selectionSet, typeNode);
         parent.TryAddNode(typeNode);
 
-        if(typeNode.Nodes.Count == 0)
+        if (typeNode.Nodes.Count == 0)
         {
             TryAddAnyLeafField(selection, typeNode);
         }
@@ -80,7 +119,7 @@ private void CollectTypes(Context context, ISelection selection, TypeContainer p
             foreach (var typeNode in parent.Nodes)
             {
                 var newParent = Expression.Convert(context.Parent, typeNode.Type);
-                var newContext = context with { Parent  = newParent, ParentType = typeNode.Type };
+                var newContext = context with { Parent = newParent, ParentType = typeNode.Type };
                 var typeCondition = Expression.TypeIs(context.Parent, typeNode.Type);
                 var selectionSet = BuildSelectionSetExpression(newContext, typeNode);
 
@@ -225,7 +264,7 @@ private void CollectSelections(
             return Expression.Bind(node.Property, propertyAccessor);
         }
 
-        if(node.IsArrayOrCollection)
+        if (node.IsArrayOrCollection)
         {
             throw new NotSupportedException("List projections are not supported.");
         }

src/HotChocolate/Core/test/Execution.Tests/Projections/ProjectableDataLoaderTests.cs

@@ -5,10 +5,6 @@
 using HotChocolate.Execution.Processing;
 using HotChocolate.Execution.TestContext;
 using HotChocolate.Types;
-<<<<<<< Updated upstream
-=======
-using HotChocolate.Types.Relay;
->>>>>>> Stashed changes
 using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.DependencyInjection;
 using Squadron;

src/HotChocolate/Core/test/Execution.Tests/Projections/__snapshots__/ProjectableDataLoaderTests.Brand_With_Name_Over_Node.md

@@ -0,0 +1,24 @@
+# Brand_With_Name_Over_Node
+
+## SQL
+
+```text
+-- @__keys_0={ '1' } (DbType = Object)
+SELECT b."Id", b."Name"
+FROM "Brands" AS b
+WHERE b."Id" = ANY (@__keys_0)
+```
+
+## Result
+
+```json
+{
+  "data": {
+    "node": {
+      "id": "QnJhbmQ6MQ==",
+      "name": "Brand0"
+    }
+  }
+}
+```
+