[Fusion] Deduplicate Requirements

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

@@ -8,6 +8,14 @@ internal sealed partial class DeferExecutionCoordinator
     private bool _isInitialized;
 #endif
 
+    [Conditional("DEBUG")]
+    private void AssertInitialized()
+    {
+#if DEBUG
+        Debug.Assert(_isInitialized);
+#endif
+    }
+
     /// <summary>
     /// Initializes the coordinator for a new execution cycle.
     /// Must be called before any other operations when leased from a pool.

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

@@ -48,7 +48,7 @@ public DeferExecutionCoordinator()
     /// </summary>
     public int Branch(int currentBranchId, Path path, DeferUsage deferUsage)
     {
-        Debug.Assert(_isInitialized);
+        AssertInitialized();
 
         var key = new DeferredBranchKey(path, deferUsage, currentBranchId);
 
@@ -74,7 +74,7 @@ public int Branch(int currentBranchId, Path path, DeferUsage deferUsage)
     /// </summary>
     public void EnqueueResult(OperationResult result)
     {
-        Debug.Assert(_isInitialized);
+        AssertInitialized();
 
         lock (_sync)
         {
@@ -89,7 +89,7 @@ public void EnqueueResult(OperationResult result)
     /// </summary>
     public void EnqueueResult(OperationResult result, int branchId)
     {
-        Debug.Assert(_isInitialized);
+        AssertInitialized();
 
         lock (_sync)
         {
@@ -110,7 +110,7 @@ public void EnqueueResult(OperationResult result, int branchId)
     public async IAsyncEnumerable<OperationResult> ReadResultsAsync(
         [EnumeratorCancellation] CancellationToken cancellationToken = default)
     {
-        Debug.Assert(_isInitialized);
+        AssertInitialized();
 
         List<OperationResult>? snapshot = null;
         await using var registration = cancellationToken.Register(_signal.Set);

src/HotChocolate/Fusion-vnext/src/Fusion.Execution/Execution/Clients/SourceSchemaHttpClient.cs

@@ -210,11 +210,20 @@ public override async IAsyncEnumerable<SourceSchemaResult> ReadAsResultStreamAsy
                     case 1:
                     {
                         var result = await response.ReadAsResultAsync(cancellationToken);
-                        var sourceSchemaResult = new SourceSchemaResult(variables[0].Path, result);
+                        var variable = variables[0];
+                        var sourceSchemaResult = new SourceSchemaResult(variable.Path, result);
 
                         configuration.OnSourceSchemaResult?.Invoke(context, node, sourceSchemaResult);
 
                         yield return sourceSchemaResult;
+
+                        foreach (var additionalPath in variable.AdditionalPaths)
+                        {
+                            var alias = sourceSchemaResult.WithPath(additionalPath);
+                            configuration.OnSourceSchemaResult?.Invoke(context, node, alias);
+                            yield return alias;
+                        }
+
                         break;
                     }
 
@@ -228,14 +237,20 @@ public override async IAsyncEnumerable<SourceSchemaResult> ReadAsResultStreamAsy
                             await foreach (var result in response.ReadAsResultStreamAsync()
                                 .WithCancellation(cancellationToken))
                             {
-                                var (path, _) = variables[requestIndex];
-
-                                var sourceSchemaResult = new SourceSchemaResult(path, result);
+                                var variable = variables[requestIndex];
+                                var sourceSchemaResult = new SourceSchemaResult(variable.Path, result);
 
                                 configuration.OnSourceSchemaResult?.Invoke(context, node, sourceSchemaResult);
 
                                 yield return sourceSchemaResult;
 
+                                foreach (var additionalPath in variable.AdditionalPaths)
+                                {
+                                    var alias = sourceSchemaResult.WithPath(additionalPath);
+                                    configuration.OnSourceSchemaResult?.Invoke(context, node, alias);
+                                    yield return alias;
+                                }
+
                                 requestIndex++;
                             }
                         }
@@ -253,23 +268,47 @@ public override async IAsyncEnumerable<SourceSchemaResult> ReadAsResultStreamAsy
                                 }
 
                                 var index = variableIndex.GetInt32();
-                                var (path, _) = variables[index];
-                                var sourceSchemaResult = new SourceSchemaResult(path, result);
+                                var variable = variables[index];
+                                var sourceSchemaResult = new SourceSchemaResult(variable.Path, result);
 
                                 configuration.OnSourceSchemaResult?.Invoke(context, node, sourceSchemaResult);
 
                                 yield return sourceSchemaResult;
+
+                                foreach (var additionalPath in variable.AdditionalPaths)
+                                {
+                                    var alias = sourceSchemaResult.WithPath(additionalPath);
+                                    configuration.OnSourceSchemaResult?.Invoke(context, node, alias);
+                                    yield return alias;
+                                }
                             }
                         }
 
                         if (errorResult is not null)
                         {
                             yield return errorResult;
 
+                            foreach (var additionalPath in variables[0].AdditionalPaths)
+                            {
+                                var alias = errorResult.WithPath(additionalPath);
+                                configuration.OnSourceSchemaResult?.Invoke(context, node, alias);
+                                yield return alias;
+                            }
+
                             for (var i = 1; i < variables.Length; i++)
                             {
-                                var (path, _) = variables[i];
-                                yield return new SourceSchemaResult(path, SourceResultDocument.CreateEmptyObject());
+                                var variable = variables[i];
+                                var sourceSchemaResult = new SourceSchemaResult(
+                                    variable.Path,
+                                    SourceResultDocument.CreateEmptyObject());
+                                yield return sourceSchemaResult;
+
+                                foreach (var additionalPath in variable.AdditionalPaths)
+                                {
+                                    var alias = sourceSchemaResult.WithPath(additionalPath);
+                                    configuration.OnSourceSchemaResult?.Invoke(context, node, alias);
+                                    yield return alias;
+                                }
                             }
                         }
 

src/HotChocolate/Fusion-vnext/src/Fusion.Execution/Execution/Clients/SourceSchemaResult.cs

@@ -8,16 +8,27 @@ public sealed class SourceSchemaResult : IDisposable
     private static ReadOnlySpan<byte> ErrorsProperty => "errors"u8;
     private static ReadOnlySpan<byte> ExtensionsProperty => "extensions"u8;
     private readonly SourceResultDocument _document;
+    private readonly bool _ownsDocument;
 
     public SourceSchemaResult(
         Path path,
         SourceResultDocument document,
         FinalMessage final = FinalMessage.Undefined)
+        : this(path, document, final, ownsDocument: true)
+    {
+    }
+
+    private SourceSchemaResult(
+        Path path,
+        SourceResultDocument document,
+        FinalMessage final,
+        bool ownsDocument)
     {
         ArgumentNullException.ThrowIfNull(path);
         ArgumentNullException.ThrowIfNull(document);
 
         _document = document;
+        _ownsDocument = ownsDocument;
         Path = path;
         Final = final;
     }
@@ -60,5 +71,13 @@ public SourceResultElement Extensions
 
     public FinalMessage Final { get; }
 
-    public void Dispose() => _document.Dispose();
+    internal SourceSchemaResult WithPath(Path path) => new(path, _document, Final, ownsDocument: false);
+
+    public void Dispose()
+    {
+        if (_ownsDocument)
+        {
+            _document.Dispose();
+        }
+    }
 }

src/HotChocolate/Fusion-vnext/src/Fusion.Execution/Execution/Nodes/OperationExecutionNode.cs

@@ -133,7 +133,14 @@ protected override async ValueTask<ExecutionStatus> OnExecuteAsync(
             context.TrackSourceSchemaClientResponse(this, response);
 
             // we read the responses from the response stream.
-            bufferLength = Math.Max(variables.Length, 1);
+            var totalPathCount = variables.Length;
+
+            for (var i = 0; i < variables.Length; i++)
+            {
+                totalPathCount += variables[i].AdditionalPaths.Length;
+            }
+
+            bufferLength = Math.Max(totalPathCount, 1);
             buffer = ArrayPool<SourceSchemaResult>.Shared.Rent(bufferLength);
 
             await foreach (var result in response.ReadAsResultStreamAsync(cancellationToken))
@@ -264,14 +271,27 @@ private static void AddErrors(
         }
         else
         {
-            var pathBufferLength = variables.Length;
+            var pathBufferLength = 0;
+
+            for (var i = 0; i < variables.Length; i++)
+            {
+                pathBufferLength += 1 + variables[i].AdditionalPaths.Length;
+            }
+
             var pathBuffer = ArrayPool<Path>.Shared.Rent(pathBufferLength);
 
             try
             {
+                var pathBufferIndex = 0;
+
                 for (var i = 0; i < variables.Length; i++)
                 {
-                    pathBuffer[i] = variables[i].Path;
+                    pathBuffer[pathBufferIndex++] = variables[i].Path;
+
+                    foreach (var additionalPath in variables[i].AdditionalPaths)
+                    {
+                        pathBuffer[pathBufferIndex++] = additionalPath;
+                    }
                 }
 
                 context.AddErrors(error, responseNames, pathBuffer.AsSpan(0, pathBufferLength));

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

@@ -362,6 +362,8 @@ public ImmutableArray<VariableValues> CreateVariableValueSets(
 
             PooledArrayWriter? buffer = null;
             VariableValues[]? variableValueSets = null;
+            Dictionary<ObjectValueNode, int>? seen = null;
+            List<Path>?[]? additionalPaths = null;
             var nextIndex = 0;
 
             foreach (var result in current)
@@ -372,10 +374,44 @@ public ImmutableArray<VariableValues> CreateVariableValueSets(
                     requiredData,
                     ref buffer);
 
-                if (variables is not null)
+                if (variables is null)
                 {
-                    variableValueSets ??= new VariableValues[current.Count];
-                    variableValueSets[nextIndex++] = new VariableValues(result.Path, variables);
+                    continue;
+                }
+
+                variableValueSets ??= new VariableValues[current.Count];
+
+                if (nextIndex > 0)
+                {
+                    seen ??= new Dictionary<ObjectValueNode, int>(VariableValueComparer.Instance)
+                    {
+                        [variableValueSets[0].Values] = 0
+                    };
+
+                    if (seen.TryGetValue(variables, out var existingIndex))
+                    {
+                        additionalPaths ??= new List<Path>?[current.Count];
+                        (additionalPaths[existingIndex] ??= []).Add(result.Path);
+                        continue;
+                    }
+
+                    seen[variables] = nextIndex;
+                }
+
+                variableValueSets[nextIndex++] = new VariableValues(result.Path, variables);
+            }
+
+            if (additionalPaths is not null)
+            {
+                for (var i = 0; i < nextIndex; i++)
+                {
+                    if (additionalPaths[i] is { } paths)
+                    {
+                        variableValueSets![i] = variableValueSets[i] with
+                        {
+                            AdditionalPaths = [.. paths]
+                        };
+                    }
                 }
             }
 

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

@@ -0,0 +1,56 @@
+using HotChocolate.Language;
+
+namespace HotChocolate.Fusion.Execution.Results;
+
+internal sealed class VariableValueComparer : IEqualityComparer<ObjectValueNode>
+{
+    public static readonly VariableValueComparer Instance = new();
+
+    public bool Equals(ObjectValueNode? x, ObjectValueNode? y)
+    {
+        if (ReferenceEquals(x, y))
+        {
+            return true;
+        }
+
+        if (x is null || y is null)
+        {
+            return false;
+        }
+
+        var xFields = x.Fields;
+        var yFields = y.Fields;
+
+        if (xFields.Count != yFields.Count)
+        {
+            return false;
+        }
+
+        // MapRequirements always creates fields in deterministic order.
+        // We only compare values, as names are equivalent for a given operation node.
+        for (var i = 0; i < xFields.Count; i++)
+        {
+            if (!SyntaxComparer.BySyntax.Equals(xFields[i].Value, yFields[i].Value))
+            {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    public int GetHashCode(ObjectValueNode obj)
+    {
+        ArgumentNullException.ThrowIfNull(obj);
+
+        var hashCode = new HashCode();
+
+        // MapRequirements creates a deterministic field order, so no field sorting is needed.
+        for (var i = 0; i < obj.Fields.Count; i++)
+        {
+            hashCode.Add(SyntaxComparer.BySyntax.GetHashCode(obj.Fields[i].Value));
+        }
+
+        return hashCode.ToHashCode();
+    }
+}

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

@@ -1,5 +1,12 @@
+using System.Collections.Immutable;
 using HotChocolate.Language;
 
 namespace HotChocolate.Fusion.Execution;
 
-public sealed record VariableValues(Path Path, ObjectValueNode Values);
+public sealed record VariableValues(Path Path, ObjectValueNode Values)
+{
+    /// <summary>
+    /// Gets the additional paths that share the same variable values as the primary <see cref="Path"/>.
+    /// </summary>
+    public ImmutableArray<Path> AdditionalPaths { get; init; } = [];
+}

src/HotChocolate/Fusion-vnext/test/Fusion.AspNetCore.Tests/__snapshots__/BookStoreTests.Fetch_Books_From_SourceSchema1_And_Authors_From_SourceSchema2.yaml

@@ -223,12 +223,6 @@ sourceSchemas:
               {
                 "__fusion_1_id": 1
               },
-              {
-                "__fusion_1_id": 2
-              },
-              {
-                "__fusion_1_id": 2
-              },
               {
                 "__fusion_1_id": 2
               }

src/HotChocolate/Fusion-vnext/test/Fusion.AspNetCore.Tests/__snapshots__/BookStoreTests.Fetch_Books_With_Variable_First_And_First_Omitted.yaml

@@ -231,12 +231,6 @@ sourceSchemas:
               {
                 "__fusion_1_id": 1
               },
-              {
-                "__fusion_1_id": 2
-              },
-              {
-                "__fusion_1_id": 2
-              },
               {
                 "__fusion_1_id": 2
               }