fix(query-core): guard against undefined pages in hasNextPage/hasPreviousPage

.changeset/guard-infinite-undefined-pages.md

@@ -0,0 +1,12 @@
+---
+'@tanstack/query-core': patch
+---
+
+fix(query-core): guard against malformed `InfiniteData` whose `pages` is `undefined`
+
+`hasNextPage`/`hasPreviousPage` only checked for a missing `data`, so a malformed
+`InfiniteData` (where `data.pages` is `undefined`) reaching `getNextPageParam`
+threw `TypeError: Cannot read properties of undefined (reading 'length')`. This
+can happen at runtime via SSR hydration or an external `setQueryData`. Guard
+`pages` before reading `.length` so these helpers return `false`/`undefined`
+instead of crashing.

packages/query-core/src/__tests__/infiniteQueryBehavior.test.tsx

@@ -1,7 +1,11 @@
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
 import { queryKey, sleep } from '@tanstack/query-test-utils'
 import { CancelledError, InfiniteQueryObserver, QueryClient } from '..'
-import { infiniteQueryBehavior } from '../infiniteQueryBehavior'
+import {
+  hasNextPage,
+  hasPreviousPage,
+  infiniteQueryBehavior,
+} from '../infiniteQueryBehavior'
 import type { InfiniteData, InfiniteQueryObserverResult, QueryCache } from '..'
 
 describe('InfiniteQueryBehavior', () => {
@@ -530,4 +534,17 @@ describe('InfiniteQueryBehavior', () => {
 
     unsubscribe()
   })
+
+  it('should not throw when data has no pages array (malformed InfiniteData)', () => {
+    const options = {
+      initialPageParam: 1,
+      getNextPageParam: () => 1,
+      getPreviousPageParam: () => 1,
+    }
+    const malformed = {} as InfiniteData<unknown>
+
+    // Should return false instead of throwing on `pages.length`.
+    expect(hasNextPage(options, malformed)).toBe(false)
+    expect(hasPreviousPage(options, malformed)).toBe(false)
+  })
 })

packages/query-core/src/infiniteQueryBehavior.ts

@@ -131,26 +131,30 @@ export function infiniteQueryBehavior<TQueryFnData, TError, TData, TPageParam>(
 
 function getNextPageParam(
   options: InfiniteQueryPageParamsOptions<any>,
-  { pages, pageParams }: InfiniteData<unknown>,
+  { pages, pageParams }: Partial<InfiniteData<unknown>>,
 ): unknown | undefined {
+  // `pages` can be undefined at runtime (hydration, `setQueryData`).
+  if (!pages?.length) return undefined
   const lastIndex = pages.length - 1
-  return pages.length > 0
-    ? options.getNextPageParam(
-        pages[lastIndex],
-        pages,
-        pageParams[lastIndex],
-        pageParams,
-      )
-    : undefined
+  return options.getNextPageParam(
+    pages[lastIndex],
+    pages,
+    pageParams?.[lastIndex],
+    pageParams ?? [],
+  )
 }
 
 function getPreviousPageParam(
   options: InfiniteQueryPageParamsOptions<any>,
-  { pages, pageParams }: InfiniteData<unknown>,
+  { pages, pageParams }: Partial<InfiniteData<unknown>>,
 ): unknown | undefined {
-  return pages.length > 0
-    ? options.getPreviousPageParam?.(pages[0], pages, pageParams[0], pageParams)
-    : undefined
+  if (!pages?.length) return undefined
+  return options.getPreviousPageParam?.(
+    pages[0],
+    pages,
+    pageParams?.[0],
+    pageParams ?? [],
+  )
 }
 
 /**