From 9ce705c5ccc5e6f4ac26af6e6471a6d2f4e995db Mon Sep 17 00:00:00 2001
From: Arda TANRIKULU <ardatanrikulu@gmail.com>
Date: Tue, 3 Dec 2024 06:10:38 -0500
Subject: [PATCH] fix(delegate): do not forward non-nullability errors to the
 gateway (#257)

---
 .changeset/slow-cars-mate.md                |  5 +++++
 packages/delegate/src/mergeFields.ts        | 13 ++++++++++++-
 packages/stitch/tests/mergeFailures.test.ts |  2 +-
 3 files changed, 18 insertions(+), 2 deletions(-)
 create mode 100644 .changeset/slow-cars-mate.md

diff --git a/.changeset/slow-cars-mate.md b/.changeset/slow-cars-mate.md
new file mode 100644
index 00000000..0f6aca4e
--- /dev/null
+++ b/.changeset/slow-cars-mate.md
@@ -0,0 +1,5 @@
+---
+'@graphql-tools/delegate': patch
+---
+
+Do not show internal non-nullability errors in the gateway
diff --git a/packages/delegate/src/mergeFields.ts b/packages/delegate/src/mergeFields.ts
index a5860926..5cd5ad80 100644
--- a/packages/delegate/src/mergeFields.ts
+++ b/packages/delegate/src/mergeFields.ts
@@ -147,7 +147,18 @@ export function handleResolverResult(
     for (const [responseKey, fieldNodes] of fields) {
       const combinedPath = [...path, responseKey];
       if (resolverResult instanceof GraphQLError) {
-        nullResult[responseKey] = relocatedError(resolverResult, combinedPath);
+        if (
+          resolverResult.message.includes(
+            'Cannot return null for non-nullable field',
+          )
+        ) {
+          nullResult[responseKey] = null;
+        } else {
+          nullResult[responseKey] = relocatedError(
+            resolverResult,
+            combinedPath,
+          );
+        }
       } else if (resolverResult instanceof Error) {
         nullResult[responseKey] = locatedError(
           resolverResult,
diff --git a/packages/stitch/tests/mergeFailures.test.ts b/packages/stitch/tests/mergeFailures.test.ts
index 9ada0b04..a56da9d0 100644
--- a/packages/stitch/tests/mergeFailures.test.ts
+++ b/packages/stitch/tests/mergeFailures.test.ts
@@ -240,7 +240,7 @@ describe('merge failures', () => {
       data: { thing: null },
       errors: [
         createGraphQLError(
-          'Cannot return null for non-nullable field Thing.id.',
+          'Cannot return null for non-nullable field Thing.description.',
         ),
       ],
     };