fix(types): normalise Function.args/kwargs None to [] / {} in __post_init__

[SuperMarioYL]

Summary

Fixes #479.

Function declares args and kwargs as Optional[List] / Optional[Dict] with default_factory=list / default_factory=dict. The defaults only apply when a field is omitted; an explicit None (which JsonOutputParser produces when the LLM omits or nullifies a field) bypasses the factory and stores None directly. Any subsequent unpack (*func.args, **func.kwargs) then raises:

TypeError: argument after * must be an iterable, not NoneType

This crash affects every call site that unpacks func.args/func.kwargs — ToolManager.execute_func, ToolManager.execute_func_async, CallFunctionTool.call, and PermissionManager.

Fix

Add Function.__post_init__ (calling super().__post_init__() to keep base-class metadata validation) that normalises None → [] for args and None → {} for kwargs. All existing and future call sites are protected without per-site guard code.

def __post_init__(self):
    super().__post_init__()
    if self.args is None:
        self.args = []
    if self.kwargs is None:
        self.kwargs = {}

Tests

Five new tests added to adalflow/tests/test_tool.py:

Test	What it checks
test_function_none_args_normalised_to_empty_list	Function(args=None) stores []
test_function_none_kwargs_normalised_to_empty_dict	Function(kwargs=None) stores {}
test_function_both_none_normalised	Both None at once
test_function_tool_call_with_none_args_does_not_raise	tool.call(*func.args, **func.kwargs) doesn't crash
test_tool_manager_execute_func_with_none_args	ToolManager.execute_func round-trip

All 29 tests in test_tool.py pass (24 pre-existing + 5 new).