fix: infer pageParam from computed queryFn with conditional skipToken

Author: danieljayasurya-praathee

packages/vue-query/src/__tests__/useInfiniteQuery.test-d.tsx

@@ -1,6 +1,7 @@
 import { describe, expectTypeOf, it } from 'vitest'
-import { computed, reactive } from 'vue-demi'
+import { computed, reactive, ref } from 'vue-demi'
 import { sleep } from '@tanstack/query-test-utils'
+import { skipToken } from '..'
 import { useInfiniteQuery } from '../useInfiniteQuery'
 import { infiniteQueryOptions } from '../infiniteQueryOptions'
 import type { InfiniteData } from '@tanstack/query-core'
@@ -127,4 +128,25 @@ describe('Discriminated union return type', () => {
       expectTypeOf(query.data).toEqualTypeOf<InfiniteData<string, unknown>>()
     }
   })
+
+  it('should infer pageParam from computed queryFn with conditional skipToken', () => {
+    const enabled = ref(false)
+
+    useInfiniteQuery({
+      queryKey: ['infiniteQuery', enabled],
+      queryFn: computed(() =>
+        enabled.value
+          ? ({ pageParam }) => {
+              expectTypeOf(pageParam).toEqualTypeOf<number>()
+              return sleep(0).then(() => 'Some data')
+            }
+          : skipToken,
+      ),
+      initialPageParam: 1,
+      getNextPageParam: (_lastPage, _allPages, lastPageParam) => {
+        expectTypeOf(lastPageParam).toEqualTypeOf<number>()
+        return lastPageParam + 1
+      },
+    })
+  })
 })

packages/vue-query/src/useInfiniteQuery.ts

@@ -9,6 +9,7 @@ import type {
   InfiniteData,
   InfiniteQueryObserverOptions,
   InfiniteQueryObserverResult,
+  QueryFunction,
   QueryKey,
   QueryObserver,
 } from '@tanstack/query-core'
@@ -24,6 +25,10 @@ import type {
 } from './types'
 import type { QueryClient } from './queryClient'
 
+// Widen the type of the symbol to preserve contextual typing for
+// `computed(() => condition ? queryFn : skipToken)`.
+type SkipTokenForUseInfiniteQuery = symbol
+
 export type UseInfiniteQueryOptions<
   TQueryFnData = unknown,
   TError = DefaultError,
@@ -48,6 +53,14 @@ export type UseInfiniteQueryOptions<
             TPageParam
           >[Property]
         >
+      : Property extends 'queryFn'
+        ? MaybeRefOrGetter<
+            QueryFunction<
+              TQueryFnData,
+              DeepUnwrapRef<TQueryKey>,
+              TPageParam
+            > | SkipTokenForUseInfiniteQuery
+          >
       : MaybeRefDeep<
           InfiniteQueryObserverOptions<
             TQueryFnData,