From 22358505db6a991a29bd476bd90ba3dd893e1cb5 Mon Sep 17 00:00:00 2001
From: Lucian Jones <lucian@movio.co>
Date: Wed, 27 Apr 2022 09:57:40 +1200
Subject: [PATCH 1/3] Add test to reproduce issue

---
 execution_test.go | 53 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 53 insertions(+)

diff --git a/execution_test.go b/execution_test.go
index 709af147..1ecb47f2 100644
--- a/execution_test.go
+++ b/execution_test.go
@@ -984,6 +984,59 @@ func TestFederatedQueryFragmentSpreads(t *testing.T) {
 		f.checkSuccess(t)
 	})
 
+	t.Run("with multiple top level fragment spreads (gadget implementation)", func(t *testing.T) {
+		f := &queryExecutionFixture{
+			services: []testService{serviceA, serviceB},
+			query: `
+			query Foo {
+				snapshot(id: "GADGET1") {
+					id
+					name
+					... GadgetFragment
+					... GizmoFragment
+				}
+			}
+
+			fragment GadgetFragment on GadgetImplementation {
+				gadgets {
+					id
+					name
+					agents {
+						name
+						... on Agent {
+							country
+						}
+					}
+				}
+			}
+
+			fragment GizmoFragment on GizmoImplementation {
+				gizmos {
+					id
+					name
+				}
+			}`,
+			expected: `
+			{
+				"snapshot": {
+					"id": "100",
+					"name": "foo",
+					"gadgets": [
+						{
+							"id": "GADGET1",
+							"name": "Gadget #1",
+							"agents": [
+								{"name": "James Bond", "country": "UK"}
+							]
+						}
+					]
+				}
+			}`,
+		}
+
+		f.checkSuccess(t)
+	})
+
 }
 
 func TestQueryExecutionMultipleServices(t *testing.T) {

From 518ba05273238d8e6cdce5517ef26e8167497f90 Mon Sep 17 00:00:00 2001
From: Lucian Jones <lucian@movio.co>
Date: Wed, 27 Apr 2022 10:02:21 +1200
Subject: [PATCH 2/3] Fix overwriting ObjectDefintion with wrong value

---
 execution.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/execution.go b/execution.go
index 38b08de2..ae9163cc 100644
--- a/execution.go
+++ b/execution.go
@@ -690,7 +690,7 @@ func (s *ExecutableSchema) evaluateSkipAndIncludeRec(vars map[string]interface{}
 					Name:             selection.Name,
 					Directives:       removeSkipAndInclude(selection.Directives),
 					Position:         selection.Position,
-					ObjectDefinition: selection.Definition.Definition,
+					ObjectDefinition: selection.ObjectDefinition,
 					Definition: &ast.FragmentDefinition{
 						Name:               selection.Definition.Name,
 						VariableDefinition: selection.Definition.VariableDefinition,

From 9e0455f46af2d06e19ee126786b710f300664944 Mon Sep 17 00:00:00 2001
From: Lucian Jones <lucian@movio.co>
Date: Wed, 27 Apr 2022 10:04:30 +1200
Subject: [PATCH 3/3] Eliminate unnecessary fragment spreads

---
 query_execution.go | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/query_execution.go b/query_execution.go
index cca15a54..fdcdb2ca 100644
--- a/query_execution.go
+++ b/query_execution.go
@@ -843,7 +843,7 @@ func unionAndTrimSelectionSetRec(objectTypename string, schema *ast.Schema, sele
 			fragment := selection
 			if fragment.ObjectDefinition.IsAbstractType() &&
 				fragmentImplementsAbstractType(schema, fragment.ObjectDefinition.Name, fragment.TypeCondition) &&
-				objectTypenameMatchesDifferentFragment(objectTypename, fragment) {
+				objectTypenameMatchesDifferentFragment(objectTypename, fragment.TypeCondition) {
 				continue
 			}
 
@@ -853,7 +853,18 @@ func unionAndTrimSelectionSetRec(objectTypename string, schema *ast.Schema, sele
 				filteredSelectionSet = append(filteredSelectionSet, selection)
 			}
 		case *ast.FragmentSpread:
-			filteredSelectionSet = append(filteredSelectionSet, selection)
+			fragment := selection
+			if fragment.ObjectDefinition.IsAbstractType() &&
+				fragmentImplementsAbstractType(schema, fragment.ObjectDefinition.Name, fragment.Definition.TypeCondition) &&
+				objectTypenameMatchesDifferentFragment(objectTypename, fragment.Definition.TypeCondition) {
+				continue
+			}
+
+			filteredSelections := unionAndTrimSelectionSetRec(objectTypename, schema, fragment.Definition.SelectionSet, seenFields)
+			if len(filteredSelections) > 0 {
+				fragment.Definition.SelectionSet = filteredSelections
+				filteredSelectionSet = append(filteredSelectionSet, selection)
+			}
 		}
 	}
 
@@ -869,6 +880,6 @@ func extractAndCastTypenameField(result map[string]interface{}) string {
 	return typeNameInterface.(string)
 }
 
-func objectTypenameMatchesDifferentFragment(typename string, fragment *ast.InlineFragment) bool {
-	return fragment.TypeCondition != typename
+func objectTypenameMatchesDifferentFragment(typename, fragmentTypeCondition string) bool {
+	return fragmentTypeCondition != typename
 }