From fc6cbe23d7c3daef069fb5e41d626d0d5c02b608 Mon Sep 17 00:00:00 2001
From: Wesley Collin Wright <wesleyw@dropbox.com>
Date: Sat, 25 Mar 2023 14:13:10 +0000
Subject: [PATCH 1/3] [dataclass_transform] fix deserialization for
 frozen_default

---
 mypy/nodes.py                                 |  2 +-
 .../fine-grained-dataclass-transform.test     | 42 +++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/mypy/nodes.py b/mypy/nodes.py
index 72a23d4f07894..d5ce8d6751272 100644
--- a/mypy/nodes.py
+++ b/mypy/nodes.py
@@ -3915,7 +3915,7 @@ def serialize(self) -> JsonDict:
             "eq_default": self.eq_default,
             "order_default": self.order_default,
             "kw_only_default": self.kw_only_default,
-            "frozen_only_default": self.frozen_default,
+            "frozen_default": self.frozen_default,
             "field_specifiers": list(self.field_specifiers),
         }
 
diff --git a/test-data/unit/fine-grained-dataclass-transform.test b/test-data/unit/fine-grained-dataclass-transform.test
index 7dc852f1d733c..3abba0892ae88 100644
--- a/test-data/unit/fine-grained-dataclass-transform.test
+++ b/test-data/unit/fine-grained-dataclass-transform.test
@@ -90,3 +90,45 @@ builtins.pyi:12: note: "B" defined here
 main:7: error: Unexpected keyword argument "y" for "B"
 builtins.pyi:12: note: "B" defined here
 ==
+
+[case frozenStays]
+# flags: --python-version 3.11
+from foo import Foo
+
+foo = Foo(base=0, foo=1)
+
+[file transform.py]
+from typing import dataclass_transform, Type
+
+@dataclass_transform(frozen_default=True)
+def dataclass(cls: Type) -> Type: return cls
+
+[file base.py]
+from transform import dataclass
+
+@dataclass
+class Base:
+    base: int
+
+[file foo.py]
+from base import Base
+from transform import dataclass
+
+@dataclass
+class Foo(Base):
+    foo: int
+
+[file foo.py.2]
+from base import Base
+from transform import dataclass
+
+@dataclass
+class Foo(Base):
+    foo: int
+    bar: int = 0
+
+[typing fixtures/typing-full.pyi]
+[builtins fixtures/dataclasses.pyi]
+
+[out]
+==

From 25d90d6426470d5e355e2cb07ad54aea99c278db Mon Sep 17 00:00:00 2001
From: Wesley Collin Wright <wesleyw@dropbox.com>
Date: Sat, 25 Mar 2023 14:15:28 +0000
Subject: [PATCH 2/3] better testcase name

---
 test-data/unit/fine-grained-dataclass-transform.test | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test-data/unit/fine-grained-dataclass-transform.test b/test-data/unit/fine-grained-dataclass-transform.test
index 3abba0892ae88..37e79236af8b4 100644
--- a/test-data/unit/fine-grained-dataclass-transform.test
+++ b/test-data/unit/fine-grained-dataclass-transform.test
@@ -91,7 +91,7 @@ main:7: error: Unexpected keyword argument "y" for "B"
 builtins.pyi:12: note: "B" defined here
 ==
 
-[case frozenStays]
+[case frozenInheritanceViaDefault]
 # flags: --python-version 3.11
 from foo import Foo
 

From 07eb500c07f3076484102f630e32f287404b3365 Mon Sep 17 00:00:00 2001
From: Wesley Collin Wright <wesleyw@dropbox.com>
Date: Sat, 25 Mar 2023 14:19:23 +0000
Subject: [PATCH 3/3] explanatory comment

---
 test-data/unit/fine-grained-dataclass-transform.test | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/test-data/unit/fine-grained-dataclass-transform.test b/test-data/unit/fine-grained-dataclass-transform.test
index 37e79236af8b4..6d37ecaf74f88 100644
--- a/test-data/unit/fine-grained-dataclass-transform.test
+++ b/test-data/unit/fine-grained-dataclass-transform.test
@@ -130,5 +130,12 @@ class Foo(Base):
 [typing fixtures/typing-full.pyi]
 [builtins fixtures/dataclasses.pyi]
 
+# If the frozen parameter is being maintained correctly, we *don't* expect to see issues; if it's
+# broken in incremental mode, then we'll see an error about inheriting a non-frozen class from a
+# frozen one.
+#
+# Ideally we'd also add a `foo.foo = 2` to confirm that frozen semantics are actually being
+# enforced, but incremental tests currently can't start with an error, which makes it tricky to
+# write such a test case.
 [out]
 ==