Fix TypeError for asdict(<class with namedtuple>, retain_collection_types=True)

changelog.d/1165.change.md

@@ -0,0 +1 @@
+Fixed serialization of namedtuple fields using `attrs.asdict/astuple()` with `retain_collection_types=True`.

src/attr/_funcs.py

@@ -72,19 +72,25 @@ def asdict(
                 )
             elif isinstance(v, (tuple, list, set, frozenset)):
                 cf = v.__class__ if retain_collection_types is True else list
-                rv[a.name] = cf(
-                    [
-                        _asdict_anything(
-                            i,
-                            is_key=False,
-                            filter=filter,
-                            dict_factory=dict_factory,
-                            retain_collection_types=retain_collection_types,
-                            value_serializer=value_serializer,
-                        )
-                        for i in v
-                    ]
-                )
+                items = [
+                    _asdict_anything(
+                        i,
+                        is_key=False,
+                        filter=filter,
+                        dict_factory=dict_factory,
+                        retain_collection_types=retain_collection_types,
+                        value_serializer=value_serializer,
+                    )
+                    for i in v
+                ]
+                try:
+                    rv[a.name] = cf(items)
+                except TypeError:
+                    if not issubclass(cf, tuple):
+                        raise
+                    # Workaround for TypeError: cf.__new__() missing 1 required
+                    # positional argument (which appears, for a namedturle)
+                    rv[a.name] = cf(*items)
             elif isinstance(v, dict):
                 df = dict_factory
                 rv[a.name] = df(
@@ -241,22 +247,26 @@ def astuple(
                 )
             elif isinstance(v, (tuple, list, set, frozenset)):
                 cf = v.__class__ if retain is True else list
-                rv.append(
-                    cf(
-                        [
-                            astuple(
-                                j,
-                                recurse=True,
-                                filter=filter,
-                                tuple_factory=tuple_factory,
-                                retain_collection_types=retain,
-                            )
-                            if has(j.__class__)
-                            else j
-                            for j in v
-                        ]
+                items = [
+                    astuple(
+                        j,
+                        recurse=True,
+                        filter=filter,
+                        tuple_factory=tuple_factory,
+                        retain_collection_types=retain,
                     )
-                )
+                    if has(j.__class__)
+                    else j
+                    for j in v
+                ]
+                try:
+                    rv.append(cf(items))
+                except TypeError:
+                    if not issubclass(cf, tuple):
+                        raise
+                    # Workaround for TypeError: cf.__new__() missing 1 required
+                    # positional argument (which appears, for a namedturle)
+                    rv.append(cf(*items))
             elif isinstance(v, dict):
                 df = v.__class__ if retain is True else dict
                 rv.append(

tests/test_funcs.py

@@ -4,9 +4,10 @@
 Tests for `attr._funcs`.
 """
 
+import re
 
 from collections import OrderedDict
-from typing import Generic, TypeVar
+from typing import Generic, NamedTuple, TypeVar
 
 import pytest
 
@@ -232,6 +233,52 @@ class A:
 
         assert {"a": {(1,): 1}} == attr.asdict(instance)
 
+    def test_named_tuple_retain_type(self):
+        """
+        Namedtuples can be serialized if retain_collection_types is True.
+
+        See #1164
+        """
+
+        class Coordinates(NamedTuple):
+            lat: float
+            lon: float
+
+        @attr.s
+        class A:
+            coords: Coordinates = attr.ib()
+
+        instance = A(Coordinates(50.419019, 30.516225))
+
+        assert {"coords": Coordinates(50.419019, 30.516225)} == attr.asdict(
+            instance, retain_collection_types=True
+        )
+
+    def test_type_error_with_retain_type(self):
+        """
+        Serialization that fails with TypeError leaves the error through if
+        they're not tuples.
+
+        See #1164
+        """
+
+        message = "__new__() missing 1 required positional argument (asdict)"
+
+        class Coordinates(list):
+            def __init__(self, first, *rest):
+                if isinstance(first, list):
+                    raise TypeError(message)
+                super().__init__([first, *rest])
+
+        @attr.s
+        class A:
+            coords: Coordinates = attr.ib()
+
+        instance = A(Coordinates(50.419019, 30.516225))
+
+        with pytest.raises(TypeError, match=re.escape(message)):
+            attr.asdict(instance, retain_collection_types=True)
+
 
 class TestAsTuple:
     """
@@ -390,6 +437,52 @@ def test_sets_no_retain(self, C, set_type):
 
         assert (1, [1, 2, 3]) == d
 
+    def test_named_tuple_retain_type(self):
+        """
+        Namedtuples can be serialized if retain_collection_types is True.
+
+        See #1164
+        """
+
+        class Coordinates(NamedTuple):
+            lat: float
+            lon: float
+
+        @attr.s
+        class A:
+            coords: Coordinates = attr.ib()
+
+        instance = A(Coordinates(50.419019, 30.516225))
+
+        assert (Coordinates(50.419019, 30.516225),) == attr.astuple(
+            instance, retain_collection_types=True
+        )
+
+    def test_type_error_with_retain_type(self):
+        """
+        Serialization that fails with TypeError leaves the error through if
+        they're not tuples.
+
+        See #1164
+        """
+
+        message = "__new__() missing 1 required positional argument (astuple)"
+
+        class Coordinates(list):
+            def __init__(self, first, *rest):
+                if isinstance(first, list):
+                    raise TypeError(message)
+                super().__init__([first, *rest])
+
+        @attr.s
+        class A:
+            coords: Coordinates = attr.ib()
+
+        instance = A(Coordinates(50.419019, 30.516225))
+
+        with pytest.raises(TypeError, match=re.escape(message)):
+            attr.astuple(instance, retain_collection_types=True)
+
 
 class TestHas:
     """