fix(merge): handle undefined interfaces array on ObjectTypeDefinitionNode #2629

Author: ardatan

.changeset/curvy-cups-help.md

@@ -0,0 +1,5 @@
+---
+'@graphql-tools/merge': patch
+---
+
+fix(merge): handle undefined interfaces array on ObjectTypeDefinitionNode #2629

packages/merge/src/typedefs-mergers/merge-named-type-array.ts

@@ -7,9 +7,9 @@ function alreadyExists(arr: ReadonlyArray<NamedTypeNode>, other: NamedTypeNode):
 }
 
 export function mergeNamedTypeArray(
-  first: ReadonlyArray<NamedTypeNode>,
-  second: ReadonlyArray<NamedTypeNode>,
-  config: Config
+  first: ReadonlyArray<NamedTypeNode> = [],
+  second: ReadonlyArray<NamedTypeNode> = [],
+  config: Config = {}
 ): NamedTypeNode[] {
   const result = [...second, ...first.filter(d => !alreadyExists(second, d))];
   if (config && config.sort) {