[Fusion] Only visit input objects once while building the execution tree

src/HotChocolate/Fusion-vnext/src/Fusion.Execution/Planning/OperationPlanner.BuildExecutionTree.cs

@@ -851,6 +851,7 @@ private static bool DoVariablesContainUploadScalar(
         ISchemaDefinition schema)
     {
         var inputObjectTypes = new Queue<IInputObjectTypeDefinition>();
+        var visited = new HashSet<IInputObjectTypeDefinition>(ReferenceEqualityComparer.Instance);
 
         foreach (var variable in variables)
         {
@@ -862,7 +863,7 @@ private static bool DoVariablesContainUploadScalar(
                 return true;
             }
 
-            if (variableType is IInputObjectTypeDefinition inputObjectType)
+            if (variableType is IInputObjectTypeDefinition inputObjectType && visited.Add(inputObjectType))
             {
                 inputObjectTypes.Enqueue(inputObjectType);
             }
@@ -879,7 +880,7 @@ private static bool DoVariablesContainUploadScalar(
                     return true;
                 }
 
-                if (fieldType is IInputObjectTypeDefinition nestedInputObjectType)
+                if (fieldType is IInputObjectTypeDefinition nestedInputObjectType && visited.Add(nestedInputObjectType))
                 {
                     inputObjectTypes.Enqueue(nestedInputObjectType);
                 }

src/HotChocolate/Fusion-vnext/test/Fusion.AspNetCore.Tests/IntegrationTests.cs

@@ -0,0 +1,53 @@
+using HotChocolate.Transport;
+using HotChocolate.Transport.Http;
+
+namespace HotChocolate.Fusion;
+
+public class IntegrationTests : FusionTestBase
+{
+    [Fact]
+    public async Task Recursive_Input_Object_Type()
+    {
+        // arrange
+        using var server1 = CreateSourceSchema(
+            "A",
+            """
+            type Query {
+              field(input: RecursiveInput!): String
+            }
+
+            input RecursiveInput {
+              child: RecursiveInput
+            }
+            """);
+
+        using var gateway = await CreateCompositeSchemaAsync(
+        [
+            ("A", server1)
+        ]);
+
+        // act
+        using var client = GraphQLHttpClient.Create(gateway.CreateClient());
+
+        var request = new OperationRequest(
+            """
+            query testQuery($input: RecursiveInput!) {
+              field(input: $input)
+            }
+            """,
+            variables: new Dictionary<string, object?>
+            {
+                ["input"] = new Dictionary<string, object?>
+                {
+                    ["child"] = null
+                }
+            });
+
+        using var result = await client.PostAsync(
+            request,
+            new Uri("http://localhost:5000/graphql"));
+
+        // assert
+        await MatchSnapshotAsync(gateway, request, result);
+    }
+}

src/HotChocolate/Fusion-vnext/test/Fusion.AspNetCore.Tests/__snapshots__/IntegrationTests.Recursive_Input_Object_Type.yaml

@@ -0,0 +1,81 @@
+title: Recursive_Input_Object_Type
+request:
+  document: |
+    query testQuery(
+      $input: RecursiveInput!
+    ) {
+      field(input: $input)
+    }
+  variables: |
+    {
+      "input": {
+        "child": null
+      }
+    }
+response:
+  body: |
+    {
+      "data": {
+        "field": "Query"
+      }
+    }
+sourceSchemas:
+  - name: A
+    schema: |
+      schema {
+        query: Query
+      }
+
+      type Query {
+        field(input: RecursiveInput!): String
+      }
+
+      input RecursiveInput {
+        child: RecursiveInput
+      }
+    interactions:
+      - request:
+          document: |
+            query testQuery_4b201a4f_1(
+              $input: RecursiveInput!
+            ) {
+              field(input: $input)
+            }
+          variables: |
+            {
+              "input": {
+                "child": null
+              }
+            }
+        response:
+          results:
+            - |
+              {
+                "data": {
+                  "field": "Query"
+                }
+              }
+operationPlan:
+  operation:
+    - document: |
+        query testQuery(
+          $input: RecursiveInput!
+        ) {
+          field(input: $input)
+        }
+      name: testQuery
+      hash: 4b201a4f390fe386d2d0db5091a152b3
+      searchSpace: 1
+      expandedNodes: 1
+  nodes:
+    - id: 1
+      type: Operation
+      schema: A
+      operation: |
+        query testQuery_4b201a4f_1(
+          $input: RecursiveInput!
+        ) {
+          field(input: $input)
+        }
+      forwardedVariables:
+        - input