bpo-34363: dataclasses.asdict() and .astuple() now handle fields which are namedtuples. (GH-9151)
diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py
index a43d076..28e9f75 100644
--- a/Lib/dataclasses.py
+++ b/Lib/dataclasses.py
@@ -1026,11 +1026,36 @@
value = _asdict_inner(getattr(obj, f.name), dict_factory)
result.append((f.name, value))
return dict_factory(result)
+ elif isinstance(obj, tuple) and hasattr(obj, '_fields'):
+ # obj is a namedtuple. Recurse into it, but the returned
+ # object is another namedtuple of the same type. This is
+ # similar to how other list- or tuple-derived classes are
+ # treated (see below), but we just need to create them
+ # differently because a namedtuple's __init__ needs to be
+ # called differently (see bpo-34363).
+
+ # I'm not using namedtuple's _asdict()
+ # method, because:
+ # - it does not recurse in to the namedtuple fields and
+ # convert them to dicts (using dict_factory).
+ # - I don't actually want to return a dict here. The the main
+ # use case here is json.dumps, and it handles converting
+ # namedtuples to lists. Admittedly we're losing some
+ # information here when we produce a json list instead of a
+ # dict. Note that if we returned dicts here instead of
+ # namedtuples, we could no longer call asdict() on a data
+ # structure where a namedtuple was used as a dict key.
+
+ return type(obj)(*[_asdict_inner(v, dict_factory) for v in obj])
elif isinstance(obj, (list, tuple)):
+ # Assume we can create an object of this type by passing in a
+ # generator (which is not true for namedtuples, handled
+ # above).
return type(obj)(_asdict_inner(v, dict_factory) for v in obj)
elif isinstance(obj, dict):
- return type(obj)((_asdict_inner(k, dict_factory), _asdict_inner(v, dict_factory))
- for k, v in obj.items())
+ return type(obj)((_asdict_inner(k, dict_factory),
+ _asdict_inner(v, dict_factory))
+ for k, v in obj.items())
else:
return copy.deepcopy(obj)
@@ -1066,7 +1091,18 @@
value = _astuple_inner(getattr(obj, f.name), tuple_factory)
result.append(value)
return tuple_factory(result)
+ elif isinstance(obj, tuple) and hasattr(obj, '_fields'):
+ # obj is a namedtuple. Recurse into it, but the returned
+ # object is another namedtuple of the same type. This is
+ # similar to how other list- or tuple-derived classes are
+ # treated (see below), but we just need to create them
+ # differently because a namedtuple's __init__ needs to be
+ # called differently (see bpo-34363).
+ return type(obj)(*[_astuple_inner(v, tuple_factory) for v in obj])
elif isinstance(obj, (list, tuple)):
+ # Assume we can create an object of this type by passing in a
+ # generator (which is not true for namedtuples, handled
+ # above).
return type(obj)(_astuple_inner(v, tuple_factory) for v in obj)
elif isinstance(obj, dict):
return type(obj)((_astuple_inner(k, tuple_factory), _astuple_inner(v, tuple_factory))