[Fusion] Pop path in case of leftover (#8450)

Author: tobias-tengler

src/HotChocolate/Fusion/src/Core/Planning/Pipeline/ExecutionStepDiscoveryMiddleware.cs

@@ -156,6 +156,7 @@ parentSelectionPath is null
 
                 if (!fieldInfo.Bindings.ContainsSubgraph(subgraph))
                 {
+                    path.RemoveAt(pathIndex);
                     (leftovers ??= []).Add(selection);
                     continue;
                 }

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

@@ -2790,6 +2790,71 @@ query testQuery {
         await snapshot.MatchMarkdownAsync();
     }
 
+    [Fact]
+    public async Task Viewer_Bug_3() {
+        // arrange
+        var subgraphA = await TestSubgraph.CreateAsync(
+            """
+            type Query {
+              viewer: Viewer!
+            }
+
+            type Viewer {
+              subgraphA: String!
+            }
+            """);
+
+        var subgraphB = await TestSubgraph.CreateAsync(
+            """
+            type Query {
+              viewer: Viewer!
+            }
+
+            type Viewer {
+              subgraphB: String!
+            }
+            """);
+
+        var subgraphC = await TestSubgraph.CreateAsync(
+            """
+            type Query {
+              subgraphC: SubgraphC!
+            }
+
+            type SubgraphC {
+              someField: String!
+              anotherField: String!
+            }
+            """);
+
+        using var subgraphs = new TestSubgraphCollection(output, [subgraphA, subgraphB, subgraphC]);
+        var executor = await subgraphs.GetExecutorAsync();
+        var request = Parse("""
+                            query {
+                              viewer {
+                                subgraphA
+                                subgraphB
+                              }
+                              subgraphC {
+                                someField
+                                anotherField
+                              }
+                            }
+                            """);
+
+        // act
+        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 Two_Arguments_Differing_Nullability_Does_Not_Duplicate_Forwarded_Variables()
     {

src/HotChocolate/Fusion/test/Core.Tests/__snapshots__/DemoIntegrationTests.Viewer_Bug_3.md

@@ -0,0 +1,82 @@
+# Viewer_Bug_3
+
+## Result
+
+```json
+{
+  "data": {
+    "viewer": {
+      "subgraphA": "string",
+      "subgraphB": "string"
+    },
+    "subgraphC": {
+      "someField": "string",
+      "anotherField": "string"
+    }
+  }
+}
+```
+
+## Request
+
+```graphql
+{
+  viewer {
+    subgraphA
+    subgraphB
+  }
+  subgraphC {
+    someField
+    anotherField
+  }
+}
+```
+
+## QueryPlan Hash
+
+```text
+0343522DE0DDC505C43E45B0E95A7AED449C0B87
+```
+
+## QueryPlan
+
+```json
+{
+  "document": "{ viewer { subgraphA subgraphB } subgraphC { someField anotherField } }",
+  "rootNode": {
+    "type": "Sequence",
+    "nodes": [
+      {
+        "type": "Parallel",
+        "nodes": [
+          {
+            "type": "Resolve",
+            "subgraph": "Subgraph_3",
+            "document": "query fetch_viewer_subgraphC_1 { subgraphC { someField anotherField } }",
+            "selectionSetId": 0
+          },
+          {
+            "type": "Resolve",
+            "subgraph": "Subgraph_1",
+            "document": "query fetch_viewer_subgraphC_2 { viewer { subgraphA } }",
+            "selectionSetId": 0
+          },
+          {
+            "type": "Resolve",
+            "subgraph": "Subgraph_2",
+            "document": "query fetch_viewer_subgraphC_3 { viewer { subgraphB } }",
+            "selectionSetId": 0
+          }
+        ]
+      },
+      {
+        "type": "Compose",
+        "selectionSetIds": [
+          0
+        ]
+      }
+    ]
+  }
+}
+```
+