Correctly handle default value for length_function param

Author: uriyyo

fastapi_pagination/async_paginator.py

@@ -29,7 +29,8 @@ async def apaginate(
     if not safe:
         check_installed_extensions()
 
-    length_function = length_function or len
+    if length_function is None:
+        length_function = len
 
     return await run_async_flow(
         generic_flow(

fastapi_pagination/paginator.py

@@ -16,7 +16,7 @@
 def paginate(
     sequence: Sequence[T],
     params: Optional[AbstractParams] = None,
-    length_function: Callable[[Sequence[T]], int] = len,
+    length_function: Optional[Callable[[Sequence[T]], int]] = None,
     *,
     safe: bool = False,
     transformer: Optional[SyncItemsTransformer] = None,
@@ -26,6 +26,9 @@ def paginate(
     if not safe:
         check_installed_extensions()
 
+    if length_function is None:
+        length_function = len
+
     return run_sync_flow(
         generic_flow(
             limit_offset_flow=flow_expr(lambda r: sequence[r.as_slice()]),