From a8774a71e2bf238509faa35b485fb556fca14571 Mon Sep 17 00:00:00 2001
From: Hynek Schlawack <hs@ox.cx>
Date: Mon, 19 Oct 2020 10:04:10 +0200
Subject: [PATCH 1/2] Treat frozensets like sets in asdict/astuple

Fixes #657
---
 src/attr/_funcs.py  | 10 +++++++---
 tests/test_funcs.py | 27 +++++++++++++++++++++++++++
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/src/attr/_funcs.py b/src/attr/_funcs.py
index 56e3fcf63..e6c930cbd 100644
--- a/src/attr/_funcs.py
+++ b/src/attr/_funcs.py
@@ -53,8 +53,10 @@ def asdict(
         v = getattr(inst, a.name)
         if filter is not None and not filter(a, v):
             continue
+
         if value_serializer is not None:
             v = value_serializer(inst, a, v)
+
         if recurse is True:
             if has(v.__class__):
                 rv[a.name] = asdict(
@@ -65,7 +67,7 @@ def asdict(
                     retain_collection_types,
                     value_serializer,
                 )
-            elif isinstance(v, (tuple, list, set)):
+            elif isinstance(v, (tuple, list, set, frozenset)):
                 cf = v.__class__ if retain_collection_types is True else list
                 rv[a.name] = cf(
                     [
@@ -127,7 +129,7 @@ def _asdict_anything(
             retain_collection_types,
             value_serializer,
         )
-    elif isinstance(val, (tuple, list, set)):
+    elif isinstance(val, (tuple, list, set, frozenset)):
         cf = val.__class__ if retain_collection_types is True else list
         rv = cf(
             [
@@ -158,6 +160,7 @@ def _asdict_anything(
         rv = val
         if value_serializer is not None:
             rv = value_serializer(None, None, rv)
+
     return rv
 
 
@@ -212,7 +215,7 @@ def astuple(
                         retain_collection_types=retain,
                     )
                 )
-            elif isinstance(v, (tuple, list, set)):
+            elif isinstance(v, (tuple, list, set, frozenset)):
                 cf = v.__class__ if retain is True else list
                 rv.append(
                     cf(
@@ -257,6 +260,7 @@ def astuple(
                 rv.append(v)
         else:
             rv.append(v)
+
     return rv if tuple_factory is list else tuple_factory(rv)
 
 
diff --git a/tests/test_funcs.py b/tests/test_funcs.py
index 4d99e06f5..20e2747e6 100644
--- a/tests/test_funcs.py
+++ b/tests/test_funcs.py
@@ -149,12 +149,26 @@ def test_lists_tuples_retain_type(self, container, C):
             retain_collection_types=True,
         )
 
+    @given(set_type=st.sampled_from((set, frozenset)))
+    def test_sets_no_retain(self, C, set_type):
+        """
+        Set types are converted to lists if retain_collection_types=False.
+        """
+        d = asdict(
+            C(1, set_type((1, 2, 3))),
+            retain_collection_types=False,
+            recurse=True,
+        )
+
+        assert {"x": 1, "y": [1, 2, 3]} == d
+
     @given(st.sampled_from(MAPPING_TYPES))
     def test_dicts(self, C, dict_factory):
         """
         If recurse is True, also recurse into dicts.
         """
         res = asdict(C(1, {"a": C(4, 5)}), dict_factory=dict_factory)
+
         assert {"x": 1, "y": {"a": {"x": 4, "y": 5}}} == res
         assert isinstance(res, dict_factory)
 
@@ -330,6 +344,19 @@ def test_roundtrip(self, cls, tuple_class):
 
         assert instance == roundtrip_instance
 
+    @given(set_type=st.sampled_from((set, frozenset)))
+    def test_sets_no_retain(self, C, set_type):
+        """
+        Set types are converted to lists if retain_collection_types=False.
+        """
+        d = astuple(
+            C(1, set_type((1, 2, 3))),
+            retain_collection_types=False,
+            recurse=True,
+        )
+
+        assert (1, [1, 2, 3]) == d
+
 
 class TestHas(object):
     """

From f278e5b6a1f8ab111b18c9f1e9712f6f9dfa6913 Mon Sep 17 00:00:00 2001
From: Hynek Schlawack <hs@ox.cx>
Date: Mon, 19 Oct 2020 10:07:39 +0200
Subject: [PATCH 2/2] Add newsfragment

---
 changelog.d/704.change.rst | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog.d/704.change.rst

diff --git a/changelog.d/704.change.rst b/changelog.d/704.change.rst
new file mode 100644
index 000000000..26b08e223
--- /dev/null
+++ b/changelog.d/704.change.rst
@@ -0,0 +1 @@
+``attr.asdict()`` and ``attr.astuple()`` now treat ``frozenset``\ s like ``set``\ s with regards to the *retain_collection_types* argument.