From 9f5f50ba546da655e21ef6126100bfbda83c1cee Mon Sep 17 00:00:00 2001
From: Jim Crist-Harif <jcristharif@gmail.com>
Date: Tue, 17 Oct 2023 00:01:41 -0500
Subject: [PATCH] Fix bug handling default values for frozen & slotted
 dataclasses

Previously there was a bug where dataclasses or attrs classes with
`slots=True, frozen=True` wouldn't be able to properly use default
values for optional fields.
---
 msgspec/_core.c       |  2 +-
 tests/test_common.py  | 15 +++++++++------
 tests/test_convert.py | 10 ++++++----
 3 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/msgspec/_core.c b/msgspec/_core.c
index 1582695f..6403d398 100644
--- a/msgspec/_core.c
+++ b/msgspec/_core.c
@@ -8049,7 +8049,7 @@ DataclassInfo_post_decode(DataclassInfo *self, PyObject *obj, PathNode *path) {
                     default_value = CALL_NO_ARGS(default_value);
                     if (default_value == NULL) return -1;
                 }
-                int status = PyObject_SetAttr(obj, name, default_value);
+                int status = PyObject_GenericSetAttr(obj, name, default_value);
                 if (is_factory) {
                     Py_DECREF(default_value);
                 }
diff --git a/tests/test_common.py b/tests/test_common.py
index 4daa23a4..d422ad44 100644
--- a/tests/test_common.py
+++ b/tests/test_common.py
@@ -2694,8 +2694,9 @@ class Example:
         ):
             dec.decode(proto.encode({"a": "bad"}))
 
+    @pytest.mark.parametrize("frozen", [False, True])
     @pytest.mark.parametrize("slots", [False, True])
-    def test_decode_dataclass_defaults(self, proto, slots):
+    def test_decode_dataclass_defaults(self, proto, frozen, slots):
         if slots:
             if not PY310:
                 pytest.skip(reason="Python 3.10+ required")
@@ -2703,7 +2704,7 @@ def test_decode_dataclass_defaults(self, proto, slots):
         else:
             kws = {}
 
-        @dataclass(**kws)
+        @dataclass(frozen=frozen, **kws)
         class Example:
             a: int
             b: int
@@ -2904,9 +2905,10 @@ class Example:
         ):
             dec.decode(proto.encode({"a": "bad"}))
 
+    @pytest.mark.parametrize("frozen", [False, True])
     @pytest.mark.parametrize("slots", [False, True])
-    def test_decode_attrs_defaults(self, proto, slots):
-        @attrs.define(slots=slots)
+    def test_decode_attrs_defaults(self, proto, frozen, slots):
+        @attrs.define(frozen=frozen, slots=slots)
         class Example:
             a: int
             b: int
@@ -2916,9 +2918,10 @@ class Example:
 
         dec = proto.Decoder(Example)
         for args in [(1, 2), (1, 2, 3), (1, 2, 3, 4), (1, 2, 3, 4, 5)]:
-            msg = Example(*args)
+            sol = Example(*args)
+            msg = dict(zip("abcde", args))
             res = dec.decode(proto.encode(msg))
-            assert res == msg
+            assert res == sol
 
         # Missing fields error
         with pytest.raises(ValidationError, match="missing required field `a`"):
diff --git a/tests/test_convert.py b/tests/test_convert.py
index d1d9f7b0..9b862f9f 100644
--- a/tests/test_convert.py
+++ b/tests/test_convert.py
@@ -1388,9 +1388,10 @@ class Ex:
 
         assert convert(msg, Ex, from_attributes=True) == Ex(1)
 
+    @pytest.mark.parametrize("frozen", [False, True])
     @pytest.mark.parametrize("slots", [False, True])
     @mapcls_and_from_attributes
-    def test_dataclass_defaults(self, slots, mapcls, from_attributes):
+    def test_dataclass_defaults(self, frozen, slots, mapcls, from_attributes):
         if slots:
             if not PY310:
                 pytest.skip(reason="Python 3.10+ required")
@@ -1398,7 +1399,7 @@ def test_dataclass_defaults(self, slots, mapcls, from_attributes):
         else:
             kws = {}
 
-        @dataclass(**kws)
+        @dataclass(frozen=frozen, **kws)
         class Example:
             a: int
             b: int
@@ -1557,10 +1558,11 @@ class Ex:
 
         assert convert(msg, Ex, from_attributes=True) == Ex(1)
 
+    @pytest.mark.parametrize("frozen", [False, True])
     @pytest.mark.parametrize("slots", [False, True])
     @mapcls_and_from_attributes
-    def test_attrs_defaults(self, slots, mapcls, from_attributes):
-        @attrs.define(slots=slots)
+    def test_attrs_defaults(self, frozen, slots, mapcls, from_attributes):
+        @attrs.define(frozen=frozen, slots=slots)
         class Example:
             a: int
             b: int