Fix node planning for interface fragments with non-Node implementors

src/HotChocolate/Fusion/src/Fusion.Execution/Planning/Partitioners/SelectionSetByTypePartitioner.cs

@@ -125,9 +125,15 @@ private void CollectSelections(
             }
             else
             {
-                foreach (var possibleType in schema.GetPossibleTypes(type, includeInaccessible: true))
+                // The branches are limited to the object types the enclosing selection set can
+                // yield, as an interface type condition can be implemented by types that are not
+                // possible types of that selection set.
+                foreach (var possibleType in schema.GetPossibleTypes(context.SharedType, includeInaccessible: true))
                 {
-                    AddSelectionsForConcreteType(context, possibleType, selectionsWithPath, cloneSelectionSets: true);
+                    if (MatchesEnclosingTypeConditions(context, possibleType))
+                    {
+                        AddSelectionsForConcreteType(context, possibleType, selectionsWithPath, cloneSelectionSets: true);
+                    }
                 }
             }
         }
@@ -137,6 +143,38 @@ private void CollectSelections(
         }
     }
 
+    /// <summary>
+    /// Determines whether the specified object type satisfies all type conditions
+    /// on the current type path.
+    /// </summary>
+    private bool MatchesEnclosingTypeConditions(Context context, FusionObjectTypeDefinition type)
+    {
+        foreach (var typeCondition in context.TypePath)
+        {
+            if (!ContainsType(schema.GetPossibleTypes(typeCondition, includeInaccessible: true), type))
+            {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    private static bool ContainsType(
+        ImmutableArray<FusionObjectTypeDefinition> possibleTypes,
+        FusionObjectTypeDefinition type)
+    {
+        foreach (var possibleType in possibleTypes)
+        {
+            if (ReferenceEquals(possibleType, type))
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
     private void AddSelectionsForConcreteType(
         Context context,
         FusionObjectTypeDefinition type,

src/HotChocolate/Fusion/test/Fusion.Execution.Tests/Planning/AbstractLookupFanoutPlanningTests.cs

@@ -61,6 +61,53 @@ ... on Book { reviewsCount }
         MatchSnapshot(plan);
     }
 
+    [Fact]
+    public void Plan_Should_Prune_NonNode_Implementor_When_InterfaceFragment_Is_In_NodeSelectionSet()
+    {
+        // arrange
+        // The Manageable fragment fans out over all Manageable implementors, but the enclosing
+        // node selection set only ever yields Node implementors, so Draft must not get a branch.
+        var schema = CreateManageableNodeSchema();
+
+        // act
+        var plan = PlanOperation(
+            schema,
+            """
+            query($id: ID!) {
+              node(id: $id) {
+                __typename
+                ... on Node { id }
+                ... on Manageable { canEdit }
+              }
+            }
+            """);
+
+        // assert
+        MatchSnapshot(plan);
+    }
+
+    [Fact]
+    public void Plan_Should_Prune_NonNode_Implementor_When_NodeSelectionSet_Has_No_Shared_Selections()
+    {
+        // arrange
+        var schema = CreateManageableNodeSchema();
+
+        // act
+        var plan = PlanOperation(
+            schema,
+            """
+            query($id: ID!) {
+              node(id: $id) {
+                __typename
+                ... on Manageable { canEdit }
+              }
+            }
+            """);
+
+        // assert
+        MatchSnapshot(plan);
+    }
+
     // sku is co-located with the products root in "a", reviews in "r", Book-only title in "books".
     private static FusionSchemaDefinition CreateProductTitleSchema()
         => ComposeSchema(
@@ -151,4 +198,23 @@ type Query {
 
             type Magazine @key(fields: "id") { id: ID! title: String }
             """);
+
+    // Ticket is both Manageable and a Node, Draft is only Manageable and has no id.
+    private static FusionSchemaDefinition CreateManageableNodeSchema()
+        => ComposeSchema(
+            """
+            # name: tickets
+            schema { query: Query }
+
+            type Query {
+              node(id: ID!): Node @lookup
+              draft: Draft
+            }
+
+            interface Node { id: ID! }
+            interface Manageable { canEdit: Boolean! }
+
+            type Ticket implements Node & Manageable { id: ID! canEdit: Boolean! }
+            type Draft implements Manageable { canEdit: Boolean! name: String }
+            """);
 }

src/HotChocolate/Fusion/test/Fusion.Execution.Tests/Planning/SelectionSetByTypePartitionerTests.cs

@@ -274,6 +274,64 @@ ... on Votable {
             """);
     }
 
+    [Fact]
+    public void Selections_On_Interface_Skips_Implementors_That_Are_Not_Possible_Types()
+    {
+        // arrange
+        var source1 = new TestSourceSchema(
+            """
+            type Query {
+                node(id: ID!): Node @lookup
+                draft: Draft
+            }
+
+            interface Node {
+                id: ID!
+            }
+
+            interface Votable {
+              viewerHasUpvoted: Boolean!
+            }
+
+            type Discussion implements Node & Votable {
+              id: ID!
+              title: String!
+              viewerHasUpvoted: Boolean!
+            }
+
+            type Draft implements Votable {
+              name: String!
+              viewerHasUpvoted: Boolean!
+            }
+            """);
+        var schema = ComposeSchema(source1);
+
+        var doc = Utf8GraphQLParser.Parse(
+            """
+            query($id: ID!) {
+                node(id: $id) {
+                    ... on Votable {
+                        viewerHasUpvoted
+                    }
+                }
+            }
+            """);
+
+        // act
+        var result = Partition(schema, doc);
+
+        // assert
+        MatchInlineSnapshot(
+            result,
+            """
+            Shared: null
+
+            Discussion: {
+              viewerHasUpvoted
+            }
+            """);
+    }
+
     [Fact]
     public void Concrete_Type_Selections_Within_Interface()
     {
@@ -399,6 +457,71 @@ ... on Votable {
             """);
     }
 
+    [Fact]
+    public void Nested_Interface_Selections_Skip_Implementors_Outside_Outer_Interface()
+    {
+        // arrange
+        // Announcement is a Node and Commentable, but not Votable, so the nested Commentable
+        // fragment must not produce an Announcement branch.
+        var source1 = new TestSourceSchema(
+            """
+            type Query {
+                node(id: ID!): Node @lookup
+            }
+
+            interface Node {
+                id: ID!
+            }
+
+            interface Votable {
+              viewerHasUpvoted: Boolean!
+            }
+
+            interface Commentable {
+              commentCount: Int!
+            }
+
+            type Discussion implements Node & Votable & Commentable {
+              id: ID!
+              viewerHasUpvoted: Boolean!
+              commentCount: Int!
+            }
+
+            type Announcement implements Node & Commentable {
+              id: ID!
+              commentCount: Int!
+            }
+            """);
+        var schema = ComposeSchema(source1);
+
+        var doc = Utf8GraphQLParser.Parse(
+            """
+            query($id: ID!) {
+                node(id: $id) {
+                    ... on Votable {
+                        ... on Commentable {
+                            commentCount
+                        }
+                    }
+                }
+            }
+            """);
+
+        // act
+        var result = Partition(schema, doc);
+
+        // assert
+        MatchInlineSnapshot(
+            result,
+            """
+            Shared: null
+
+            Discussion: {
+              commentCount
+            }
+            """);
+    }
+
     [Fact]
     public void Spread_On_Type_Of_SelectionSet_Is_Part_Of_Shared_Selections()
     {

src/HotChocolate/Fusion/test/Fusion.Execution.Tests/Planning/__snapshots__/AbstractLookupFanoutPlanningTests.Plan_Should_Prune_NonNode_Implementor_When_InterfaceFragment_Is_In_NodeSelectionSet.yaml

@@ -0,0 +1,53 @@
+operation:
+  - document: |
+      query($id: ID!) {
+        node(id: $id) {
+          __typename
+          id
+          ... on Manageable {
+            canEdit
+          }
+        }
+      }
+    hash: 123456789101112
+    searchSpace: 1
+    expandedNodes: 1
+nodes:
+  - id: 1
+    type: Node
+    idValue: $id
+    responseName: node
+    branches:
+      - Ticket: 3
+    fallback: 2
+  - id: 2
+    type: Operation
+    operation: |
+      query Op_123456789101112_2($id: ID!) {
+        node(id: $id) {
+          __typename
+          id
+        }
+      }
+    forwardedVariables:
+      - id
+    dependencies:
+      - id: 1
+  - id: 3
+    type: Operation
+    schema: tickets
+    operation: |
+      query Op_123456789101112_3($id: ID!) {
+        node(id: $id) {
+          __typename
+          ... on Ticket {
+            __typename
+            id
+            canEdit
+          }
+        }
+      }
+    forwardedVariables:
+      - id
+    dependencies:
+      - id: 1

src/HotChocolate/Fusion/test/Fusion.Execution.Tests/Planning/__snapshots__/AbstractLookupFanoutPlanningTests.Plan_Should_Prune_NonNode_Implementor_When_NodeSelectionSet_Has_No_Shared_Selections.yaml

@@ -0,0 +1,50 @@
+operation:
+  - document: |
+      query($id: ID!) {
+        node(id: $id) {
+          __typename
+          ... on Manageable {
+            canEdit
+          }
+        }
+      }
+    hash: 123456789101112
+    searchSpace: 1
+    expandedNodes: 1
+nodes:
+  - id: 1
+    type: Node
+    idValue: $id
+    responseName: node
+    branches:
+      - Ticket: 3
+    fallback: 2
+  - id: 2
+    type: Operation
+    operation: |
+      query Op_123456789101112_2($id: ID!) {
+        node(id: $id) {
+          __typename
+        }
+      }
+    forwardedVariables:
+      - id
+    dependencies:
+      - id: 1
+  - id: 3
+    type: Operation
+    schema: tickets
+    operation: |
+      query Op_123456789101112_3($id: ID!) {
+        node(id: $id) {
+          __typename
+          ... on Ticket {
+            __typename
+            canEdit
+          }
+        }
+      }
+    forwardedVariables:
+      - id
+    dependencies:
+      - id: 1