From 31b8fb2f7e8549f3e6149796cf06acf464b5f0b1 Mon Sep 17 00:00:00 2001
From: Ben Newman <ben@apollographql.com>
Date: Sat, 10 Mar 2018 10:30:31 -0500
Subject: [PATCH] Fix bug in healSchema that sometimes removed '__'-prefixed
 types.

---
 src/schemaVisitor.ts | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/schemaVisitor.ts b/src/schemaVisitor.ts
index 47018dea454..b94338d257e 100644
--- a/src/schemaVisitor.ts
+++ b/src/schemaVisitor.ts
@@ -353,7 +353,8 @@ export function healSchema(schema: GraphQLSchema) {
         // Dangling references to renamed types should remain in the schema
         // during healing, but must be removed now, so that the following
         // invariant holds for all names: schema.getType(name).name === name
-        if (! hasOwn.call(actualNamedTypeMap, typeName)) {
+        if (! typeName.startsWith('__') &&
+            ! hasOwn.call(actualNamedTypeMap, typeName)) {
           return null;
         }
       });