feat(query-core): require initialValue when using custom reducer in streamedQuery

gobbimar · gobbimar · commit 42b9908c19ea · 2025-08-28T00:13:31.000+02:00
Add type safety by making initialValue mandatory when providing a custom
reducer function. This prevents runtime errors and ensures proper data
initialization for custom data structures beyond simple arrays.

Use conditional types to enforce the relationship between reducer and
initialValue parameters, maintaining backward compatibility for simple
array-based streaming while requiring explicit initialization for
custom reducers.

BREAKING CHANGE: When using a custom reducer function with streamedQuery,
the initialValue parameter is now required and must be provided.
diff --git a/packages/query-core/src/streamedQuery.ts b/packages/query-core/src/streamedQuery.ts
@@ -41,22 +41,16 @@ export function streamedQuery<
   TQueryFnData = unknown,
   TData = Array<TQueryFnData>,
   TQueryKey extends QueryKey = QueryKey,
->(params: StreamedQueryParams<TQueryFnData, TData, TQueryKey>): QueryFunction<
+>({
+  queryFn,
+  refetchMode = 'reset',
+  reducer = (items, chunk) => addToEnd(items as Array<TQueryFnData>, chunk) as TData,
+  initialValue = [] as TData,
+}: StreamedQueryParams<TQueryFnData, TData, TQueryKey>): QueryFunction<
   TData,
   TQueryKey
 > {
-  let reducer;
-  let initialValue;
-  const {refetchMode='reset', queryFn} = params;
   
-  if('reducer' in params && typeof params.reducer === 'function'){
-    reducer=params.reducer;
-    initialValue=params.initialValue;
-  }else{
-    initialValue=[] as TData;
-    reducer=(items: TData, chunk: TQueryFnData) => addToEnd(items as Array<TQueryFnData>, chunk) as TData;
-  }
-
   return async (context) => {
     const query = context.client
       .getQueryCache()
