From 02bfb4a8e3630d734f07b804b55cf3865a7169a5 Mon Sep 17 00:00:00 2001
From: Marc-Andre Giroux <mgiroux@netflix.com>
Date: Wed, 2 Jul 2025 11:38:30 -0400
Subject: [PATCH] implement a new checkForTypeExtensionFieldUniqueness

---
 .../idl/SchemaTypeExtensionsChecker.java      | 38 +++++++++++++++----
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/src/main/java/graphql/schema/idl/SchemaTypeExtensionsChecker.java b/src/main/java/graphql/schema/idl/SchemaTypeExtensionsChecker.java
index 36b4a2c3ff..1a11912811 100644
--- a/src/main/java/graphql/schema/idl/SchemaTypeExtensionsChecker.java
+++ b/src/main/java/graphql/schema/idl/SchemaTypeExtensionsChecker.java
@@ -24,10 +24,13 @@
 import graphql.schema.idl.errors.TypeExtensionMissingBaseTypeError;
 import graphql.util.FpKit;
 
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Set;
 import java.util.function.Consumer;
+import java.util.function.Function;
 import java.util.stream.Collectors;
 
 import static graphql.schema.idl.SchemaTypeChecker.checkNamedUniqueness;
@@ -81,12 +84,13 @@ private void checkObjectTypeExtensions(List<GraphQLError> errors, TypeDefinition
                                         checkNamedUniqueness(errors, directive.getArguments(), Argument::getName,
                                                 (argumentName, argument) -> new NonUniqueArgumentError(extension, fld, argumentName))));
 
-                                //
                                 // fields must be unique within a type extension
-                                forEachBut(extension, extensions,
-                                        otherTypeExt -> checkForFieldRedefinition(errors, otherTypeExt, otherTypeExt.getFieldDefinitions(), fieldDefinitions));
+                                checkForTypeExtensionFieldUniqueness(
+                                        errors,
+                                        extensions,
+                                        ObjectTypeDefinition::getFieldDefinitions
+                                );
 
-                                //
                                 // then check for field re-defs from the base type
                                 Optional<ObjectTypeDefinition> baseTypeOpt = typeRegistry.getType(extension.getName(), ObjectTypeDefinition.class);
                                 baseTypeOpt.ifPresent(baseTypeDef -> checkForFieldRedefinition(errors, extension, fieldDefinitions, baseTypeDef.getFieldDefinitions()));
@@ -125,10 +129,12 @@ private void checkInterfaceTypeExtensions(List<GraphQLError> errors, TypeDefinit
                                 checkNamedUniqueness(errors, directive.getArguments(), Argument::getName,
                                         (argumentName, argument) -> new NonUniqueArgumentError(extension, fld, argumentName))));
 
-                        //
                         // fields must be unique within a type extension
-                        forEachBut(extension, extensions,
-                                otherTypeExt -> checkForFieldRedefinition(errors, otherTypeExt, otherTypeExt.getFieldDefinitions(), fieldDefinitions));
+                        checkForTypeExtensionFieldUniqueness(
+                                errors,
+                                extensions,
+                                InterfaceTypeDefinition::getFieldDefinitions
+                        );
 
                         //
                         // then check for field re-defs from the base type
@@ -138,6 +144,24 @@ private void checkInterfaceTypeExtensions(List<GraphQLError> errors, TypeDefinit
                 });
     }
 
+    private <T extends TypeDefinition<?>> void checkForTypeExtensionFieldUniqueness(
+            List<GraphQLError> errors,
+            List<T> extensions,
+            Function<T, List<FieldDefinition>> getFieldDefinitions
+    ) {
+        Set<String> seenFields = new HashSet<>();
+
+        for (T extension : extensions) {
+            for (FieldDefinition field : getFieldDefinitions.apply(extension)) {
+                if (seenFields.contains(field.getName())) {
+                    errors.add(new TypeExtensionFieldRedefinitionError(extension, field));
+                } else {
+                    seenFields.add(field.getName());
+                }
+            }
+        }
+    }
+
     /*
      * Union type extensions have the potential to be invalid if incorrectly defined.
      *