From 3fb81ef43bca83ecbba9bb0a6f54825d648485e3 Mon Sep 17 00:00:00 2001
From: Sasha <64744993+r1tsuu@users.noreply.github.com>
Date: Mon, 5 May 2025 16:12:44 +0300
Subject: [PATCH] fix(graphql):  `nextPage` and `prevPage` are non nullable
 even though they can be `null` sometimes (#12201)

This PR introduced https://github.com/payloadcms/payload/pull/11952
improvement for graphql schema with making fields of the `Paginated<T>`
interface non-nullable.

However, there are a few special ones - `nextPage` and `prevPage`. They
can be `null` when:
The result returned 0 docs.
The result returned `x` docs, but in the DB we don't have `x+1` doc.
Thus, `nextPage` will be `null`. The result will have `nextPage: null`.
Finally, when we query 1st page, `prevPage` is `null` as well.

<img width="873" alt="image"
src="https://github.com/user-attachments/assets/04d04b13-ac26-4fc1-b421-b5f86efc9b65"
/>
---
 .../src/schema/buildPaginatedListType.ts      |  4 +-
 test/graphql/int.spec.ts                      | 45 +++++++++++++++++++
 2 files changed, 47 insertions(+), 2 deletions(-)

diff --git a/packages/graphql/src/schema/buildPaginatedListType.ts b/packages/graphql/src/schema/buildPaginatedListType.ts
index 343fd28cba..2a8a64c5d1 100644
--- a/packages/graphql/src/schema/buildPaginatedListType.ts
+++ b/packages/graphql/src/schema/buildPaginatedListType.ts
@@ -10,11 +10,11 @@ export const buildPaginatedListType = (name, docType) =>
       hasNextPage: { type: new GraphQLNonNull(GraphQLBoolean) },
       hasPrevPage: { type: new GraphQLNonNull(GraphQLBoolean) },
       limit: { type: new GraphQLNonNull(GraphQLInt) },
-      nextPage: { type: new GraphQLNonNull(GraphQLInt) },
+      nextPage: { type: GraphQLInt },
       offset: { type: GraphQLInt },
       page: { type: new GraphQLNonNull(GraphQLInt) },
       pagingCounter: { type: new GraphQLNonNull(GraphQLInt) },
-      prevPage: { type: new GraphQLNonNull(GraphQLInt) },
+      prevPage: { type: GraphQLInt },
       totalDocs: { type: new GraphQLNonNull(GraphQLInt) },
       totalPages: { type: new GraphQLNonNull(GraphQLInt) },
     },
diff --git a/test/graphql/int.spec.ts b/test/graphql/int.spec.ts
index ab4cfbdd69..6006887fb7 100644
--- a/test/graphql/int.spec.ts
+++ b/test/graphql/int.spec.ts
@@ -104,5 +104,50 @@ describe('graphql', () => {
 
       expect(res.hyphenated_name).toStrictEqual('example-hyphenated-name')
     })
+
+    it('should not error because of non nullable fields', async () => {
+      await payload.delete({ collection: 'posts', where: {} })
+
+      // this is an array if any errors
+      const res_1 = await restClient
+        .GRAPHQL_POST({
+          body: JSON.stringify({
+            query: `
+query {
+  Posts {
+    docs {
+      title
+    }
+    prevPage
+  }
+}
+        `,
+          }),
+        })
+        .then((res) => res.json())
+      expect(res_1.errors).toBeFalsy()
+
+      await payload.create({
+        collection: 'posts',
+        data: { title: 'any-title' },
+      })
+
+      const res_2 = await restClient
+        .GRAPHQL_POST({
+          body: JSON.stringify({
+            query: `
+query {
+  Posts(limit: 1) {
+    docs {
+      title
+    }
+  }
+}
+        `,
+          }),
+        })
+        .then((res) => res.json())
+      expect(res_2.errors).toBeFalsy()
+    })
   })
 })