Fix payload generator for lists and dicts. (Add more comments in this util)

aiogram/utils/payload.py

@@ -2,10 +2,19 @@ import datetime
 
 from . import json
 
-DEFAULT_FILTER = ['self']
+DEFAULT_FILTER = ['self', 'cls']
 
 
 def generate_payload(exclude=None, **kwargs):
+    """
+    Generate payload
+
+    Usage: payload = generate_payload(**locals(), exclude=['foo'])
+
+    :param exclude:
+    :param kwargs:
+    :return: dict
+    """
     if exclude is None:
         exclude = []
     return {key: value for key, value in kwargs.items() if
@@ -14,13 +23,33 @@ def generate_payload(exclude=None, **kwargs):
             and not key.startswith('_')}
 
 
+def _normalize(obj):
+    """
+    Normalize dicts and lists
+
+    :param obj:
+    :return: normalized object
+    """
+    if isinstance(obj, list):
+        return [_normalize(item) for item in obj]
+    elif isinstance(obj, dict):
+        return {k: _normalize(v) for k, v in obj.items() if v is not None}
+    elif hasattr(obj, 'to_python'):
+        return obj.to_python()
+    return obj
+
+
 def prepare_arg(value):
+    """
+    Stringify dicts/lists and convert datetime/timedelta to unix-time
+
+    :param value:
+    :return:
+    """
     if value is None:
         return value
-    elif isinstance(value, (list, dict)):
-        return json.dumps(value)
-    elif hasattr(value, 'to_python'):
-        return json.dumps(value.to_python())
+    elif isinstance(value, (list, dict)) or hasattr(value, 'to_python'):
+        return json.dumps(_normalize(value))
     elif isinstance(value, datetime.timedelta):
         now = datetime.datetime.now()
         return int((now + value).timestamp())