From 44d01fd491bc79a71d87185ef72323326e43dd6a Mon Sep 17 00:00:00 2001
From: Hendrik Volschenk <hendrik.volschenk@coolblue.nl>
Date: Wed, 18 Mar 2026 16:25:42 +0100
Subject: [PATCH] fix(federation): add reference resolver type to resolver map

Fixes #2205 by adding a type definition for `__resolveReference`
to the existing `GraphQLResolverMap` interface.
---
 subgraph-js/src/schema-helper/resolverMap.ts | 9 ++++++---
 subgraph-js/src/schemaExtensions.ts          | 4 ++--
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/subgraph-js/src/schema-helper/resolverMap.ts b/subgraph-js/src/schema-helper/resolverMap.ts
index 2fd7ae5b2..2bf2d3385 100644
--- a/subgraph-js/src/schema-helper/resolverMap.ts
+++ b/subgraph-js/src/schema-helper/resolverMap.ts
@@ -1,4 +1,5 @@
 import { GraphQLFieldResolver, GraphQLScalarType, DocumentNode } from 'graphql';
+import type { GraphQLReferenceResolver } from '../schemaExtensions';
 
 export interface GraphQLSchemaModule {
   typeDefs: DocumentNode;
@@ -6,9 +7,9 @@ export interface GraphQLSchemaModule {
 }
 
 // eslint-disable-next-line @typescript-eslint/ban-types
-export interface GraphQLResolverMap<TContext = {}> {
+export interface GraphQLResolverMap<TContext = {}, TReference extends object = any> {
   [typeName: string]:
-    | {
+    | ({
         [fieldName: string]:
           | GraphQLFieldResolver<any, TContext>
           | {
@@ -16,7 +17,9 @@ export interface GraphQLResolverMap<TContext = {}> {
               resolve?: GraphQLFieldResolver<any, TContext>;
               subscribe?: GraphQLFieldResolver<any, TContext>;
             };
-      }
+      } & {
+        __resolveReference?: GraphQLReferenceResolver<TContext, TReference>;
+      })
     | GraphQLScalarType
     | {
         [enumValue: string]: string | number;
diff --git a/subgraph-js/src/schemaExtensions.ts b/subgraph-js/src/schemaExtensions.ts
index 3c7d9d57f..92aabe11e 100644
--- a/subgraph-js/src/schemaExtensions.ts
+++ b/subgraph-js/src/schemaExtensions.ts
@@ -5,8 +5,8 @@ import {
   GraphQLUnionTypeExtensions
 } from 'graphql';
 
-export type GraphQLReferenceResolver<TContext> = (
-  reference: object,
+export type GraphQLReferenceResolver<TContext, TReference extends object = any> = (
+  reference: TReference,
   context: TContext,
   info: GraphQLResolveInfo,
 ) => any;