[Fusion] Fix null being returned for batch item (#8383)

Author: tobias-tengler

src/HotChocolate/Fusion/src/Core/Execution/Nodes/ResolveByKeyBatch.cs

@@ -142,12 +142,12 @@ private static void InitializeRequests(FusionExecutionContext context, List<Exec
     private void ProcessResult(
         FusionExecutionContext context,
         GraphQLResponse response,
-        BatchExecutionState[] batchExecutionState,
+        List<BatchExecutionState> batchExecutionState,
         string subgraphName)
     {
         var result = UnwrapResult(response, Requires);
-        ref var batchState = ref MemoryMarshal.GetArrayDataReference(batchExecutionState);
-        ref var end = ref Unsafe.Add(ref batchState, batchExecutionState.Length);
+        ref var batchState = ref MemoryMarshal.GetReference(CollectionsMarshal.AsSpan(batchExecutionState));
+        ref var end = ref Unsafe.Add(ref batchState, batchExecutionState.Count);
         var pathLength = Path.Length;
         var first = true;
 
@@ -195,13 +195,13 @@ private void ProcessResult(
     }
 
     private static Dictionary<string, IValueNode> BuildVariables(
-        BatchExecutionState[] batchExecutionState,
+        List<BatchExecutionState> batchExecutionState,
         string[] requires,
         Dictionary<string, ITypeNode> argumentTypes)
     {
         var first = batchExecutionState[0];
 
-        if (batchExecutionState.Length == 1)
+        if (batchExecutionState.Count == 1)
         {
             return first.VariableValues;
         }
@@ -210,8 +210,8 @@ private static Dictionary<string, IValueNode> BuildVariables(
         var uniqueState = new List<BatchExecutionState>();
         var processed = new HashSet<string>();
 
-        ref var batchState = ref MemoryMarshal.GetArrayDataReference(batchExecutionState);
-        ref var end = ref Unsafe.Add(ref batchState, batchExecutionState.Length);
+        ref var batchState = ref MemoryMarshal.GetReference(CollectionsMarshal.AsSpan(batchExecutionState));
+        ref var end = ref Unsafe.Add(ref batchState, batchExecutionState.Count);
 
         while (Unsafe.IsAddressLessThan(ref batchState, ref end))
         {
@@ -339,44 +339,38 @@ private static JsonElement LiftData(JsonElement data, string[] path)
         return current;
     }
 
-    private static BatchExecutionState[] CreateBatchBatchState(List<ExecutionState> executionState, string[] requires)
+    private static List<BatchExecutionState> CreateBatchBatchState(List<ExecutionState> executionState, string[] requires)
     {
-        var batchExecutionState = new BatchExecutionState[executionState.Count];
+        var batchExecutionState = new List<BatchExecutionState>(executionState.Count);
 
         ref var state = ref MemoryMarshal.GetReference(CollectionsMarshal.AsSpan(executionState));
-        ref var batchState = ref MemoryMarshal.GetArrayDataReference(batchExecutionState);
         ref var end = ref Unsafe.Add(ref state, executionState.Count);
 
         if (requires.Length == 1)
         {
             while (Unsafe.IsAddressLessThan(ref state, ref end))
             {
-                var key = FormatKeyValue(state.VariableValues[requires[0]]);
-                batchState = new BatchExecutionState(key, state);
+                if (state.VariableValues.ContainsKey(requires[0]))
+                {
+                    var key = FormatKeyValue(state.VariableValues[requires[0]]);
+                    var batchState = new BatchExecutionState(key, state);
+
+                    batchExecutionState.Add(batchState);
+                }
 
                 state = ref Unsafe.Add(ref state, 1)!;
-                batchState = ref Unsafe.Add(ref batchState, 1)!;
             }
         }
         else
         {
-            var keyBuilder = new StringBuilder();
-
             while (Unsafe.IsAddressLessThan(ref state, ref end))
             {
-                ref var key = ref MemoryMarshal.GetArrayDataReference(requires);
-                ref var keyEnd = ref Unsafe.Add(ref key, requires.Length);
-
-                while (Unsafe.IsAddressLessThan(ref key, ref keyEnd))
-                {
-                    keyBuilder.Append(FormatKeyValue(state.VariableValues[key]));
-                    key = ref Unsafe.Add(ref key, 1)!;
-                }
+                var lastKey = requires[^1];
+                var batchState = new BatchExecutionState(lastKey, state);
 
-                batchState = new BatchExecutionState(key, state);
+                batchExecutionState.Add(batchState);
 
                 state = ref Unsafe.Add(ref state, 1)!;
-                batchState = ref Unsafe.Add(ref batchState, 1)!;
             }
         }
 

src/HotChocolate/Fusion/test/Core.Tests/DemoIntegrationTests.cs

@@ -134,21 +134,21 @@ type Product implements Node {
         using var subgraphs = new TestSubgraphCollection(output, [subgraphA, subgraphB]);
         var executor = await subgraphs.GetExecutorAsync();
         var request = Parse("""
-                      query {
-                        productsA {
-                          id
-                          name
-                          price
-                          reviewCount
-                        }
-                        productsB {
-                          id
-                          name
-                          price
-                          reviewCount
-                        }
-                      }
-                      """);
+                            query {
+                              productsA {
+                                id
+                                name
+                                price
+                                reviewCount
+                              }
+                              productsB {
+                                id
+                                name
+                                price
+                                reviewCount
+                              }
+                            }
+                            """);
 
         // act
         var result = await executor.ExecuteAsync(
@@ -260,10 +260,10 @@ public async Task Authors_And_Reviews_Query_GetUserReviews_Report_Cost()
         // act
         var fusionGraph = await new FusionGraphComposer(logFactory: _logFactory)
             .ComposeAsync(
-                [
-                    demoProject.Reviews2.ToConfiguration(Reviews2ExtensionWithCostSdl),
-                    demoProject.Accounts.ToConfiguration(AccountsExtensionWithCostSdl)
-                ]);
+            [
+                demoProject.Reviews2.ToConfiguration(Reviews2ExtensionWithCostSdl),
+                demoProject.Accounts.ToConfiguration(AccountsExtensionWithCostSdl)
+            ]);
 
         var executor = await new ServiceCollection()
             .AddSingleton(demoProject.HttpClientFactory)
@@ -1656,11 +1656,7 @@ public async Task Forward_Nested_Variables_No_OpName()
                 .New()
                 .SetDocument(request)
                 .SetVariableValues(
-                    new Dictionary<string, object?>
-                    {
-                        { "id", "UHJvZHVjdDox" },
-                        { "first", 1 },
-                    })
+                    new Dictionary<string, object?> { { "id", "UHJvZHVjdDox" }, { "first", 1 }, })
                 .Build());
 
         // assert
@@ -2028,10 +2024,7 @@ public async Task GetFirstPage_With_After_Null()
 
         // act
         var fusionGraph = await new FusionGraphComposer(logFactory: _logFactory).ComposeAsync(
-            new[]
-            {
-                demoProject.Appointment.ToConfiguration(),
-            },
+            new[] { demoProject.Appointment.ToConfiguration(), },
             new FusionFeatureCollection(FusionFeatures.NodeField));
 
         var executor = await new ServiceCollection()
@@ -2232,6 +2225,114 @@ type ResaleSurveyFeedback {
         await snapshot.MatchMarkdownAsync();
     }
 
+    [Fact]
+    public async Task BatchExecutionState_With_Multiple_Variable_Values_Some_Items_Null()
+    {
+        // arrange
+        var subgraphA = await TestSubgraph.CreateAsync(
+            """
+            type Query {
+              node(id: ID!): Node
+              nodes(ids: [ID!]!): [Node]!
+            }
+
+            interface Node {
+              id: ID!
+            }
+
+            type User implements Node {
+              id: ID!
+              displayName: String!
+            }
+            """);
+        var subgraphB = await TestSubgraph.CreateAsync(
+            """
+            type Query {
+              node(id: ID!): Node
+              nodes(ids: [ID!]!): [Node]! @null(atIndex: 1)
+              userBySlug(slug: String!): User
+            }
+
+            interface Node {
+              id: ID!
+            }
+
+            type User implements Node {
+              relativeUrl: String!
+              id: ID!
+            }
+            """);
+        var subgraphC = await TestSubgraph.CreateAsync(
+            """
+            type Query {
+              node(id: ID!): Node
+              nodes(ids: [ID!]!): [Node]!
+            }
+
+            interface Node {
+              id: ID!
+            }
+
+            type User implements Node {
+              id: ID!
+              feedbacks: FeedbacksConnection
+            }
+
+            type FeedbacksConnection {
+              edges: [FeedbacksEdge!]
+            }
+
+            type FeedbacksEdge {
+              node: ResaleFeedback!
+            }
+
+            type ResaleFeedback implements Node {
+              feedback: ResaleSurveyFeedback
+              id: ID!
+            }
+
+            type ResaleSurveyFeedback {
+              buyer: User
+            }
+            """);
+
+        using var subgraphs = new TestSubgraphCollection(output, [subgraphA, subgraphB, subgraphC]);
+        var executor = await subgraphs.GetExecutorAsync();
+
+        var request = Parse(
+            """
+            query {
+              userBySlug(slug: "me") {
+                feedbacks {
+                  edges {
+                    node {
+                      feedback {
+                        buyer {
+                          relativeUrl
+                          displayName
+                        }
+                      }
+                    }
+                  }
+                }
+              }
+            }
+
+            """);
+
+        // act
+        await using var result = await executor.ExecuteAsync(
+            OperationRequestBuilder
+                .New()
+                .SetDocument(request)
+                .Build());
+
+        // assert
+        var snapshot = new Snapshot();
+        CollectSnapshotData(snapshot, request, result);
+        await snapshot.MatchMarkdownAsync();
+    }
+
     [Fact]
     public async Task BatchExecutionState_With_Multiple_Variable_Values_And_Forwarded_Variable()
     {
@@ -2401,10 +2502,7 @@ type Query {
                   }
                 }
                 """)
-            .SetVariableValues(new Dictionary<string, object?>
-            {
-                ["productId"] = "UHJvZHVjdAppMzg2MzE4NTk="
-            })
+            .SetVariableValues(new Dictionary<string, object?> { ["productId"] = "UHJvZHVjdAppMzg2MzE4NTk=" })
             .Build();
 
         // act
@@ -2478,10 +2576,7 @@ type Query {
                   }
                 }
                 """)
-            .SetVariableValues(new Dictionary<string, object?>
-            {
-                ["productId"] = "UHJvZHVjdAppMzg2MzE4NTk="
-            })
+            .SetVariableValues(new Dictionary<string, object?> { ["productId"] = "UHJvZHVjdAppMzg2MzE4NTk=" })
             .Build();
 
         // act
@@ -2559,10 +2654,7 @@ type Query {
                   }
                 }
                 """)
-            .SetVariableValues(new Dictionary<string, object?>
-            {
-                ["productId"] = "UHJvZHVjdAppMzg2MzE4NTk="
-            })
+            .SetVariableValues(new Dictionary<string, object?> { ["productId"] = "UHJvZHVjdAppMzg2MzE4NTk=" })
             .Build();
 
         // act
@@ -2580,10 +2672,7 @@ public async Task Two_Arguments_Differing_Nullability_Does_Not_Duplicate_Forward
 
         // act
         var fusionGraph = await new FusionGraphComposer(logFactory: _logFactory).ComposeAsync(
-            new[]
-            {
-                demoProject.Accounts.ToConfiguration(AccountsExtensionSdl)
-            });
+            new[] { demoProject.Accounts.ToConfiguration(AccountsExtensionSdl) });
 
         var executor = await new ServiceCollection()
             .AddSingleton(demoProject.HttpClientFactory)