From 0dd009441414ae3c37030b7b4d2fbcacea67413e Mon Sep 17 00:00:00 2001
From: Savio Mak <96855131+Glinte@users.noreply.github.com>
Date: Fri, 8 Aug 2025 13:55:04 +0800
Subject: [PATCH] Allow deletion of frozen fields

---
 semimutable/__init__.py             | 11 +++++++++++
 tests/test_semimutable_dataclass.py | 11 +++++++++++
 2 files changed, 22 insertions(+)

diff --git a/semimutable/__init__.py b/semimutable/__init__.py
index 57078d2..2dd0bbd 100644
--- a/semimutable/__init__.py
+++ b/semimutable/__init__.py
@@ -94,6 +94,17 @@ def __set__(self, instance: object, value: T) -> None:
 
         setattr(instance, self._private_name, value)
 
+    def __delete__(self, instance: object) -> None:
+        try:
+            delattr(instance, self._private_name)
+        except AttributeError:
+            pass
+        public_name = self._private_name[len(FROZEN_PREFIX) :]
+        try:
+            instance.__dict__.pop(public_name, None)
+        except AttributeError:
+            pass
+
 
 error = RuntimeError(
     "This field is created via field(frozen=True) but the @semimutable.dataclass decorator is not used on the dataclass. "
diff --git a/tests/test_semimutable_dataclass.py b/tests/test_semimutable_dataclass.py
index 52e0087..33b093c 100644
--- a/tests/test_semimutable_dataclass.py
+++ b/tests/test_semimutable_dataclass.py
@@ -27,6 +27,17 @@ class Sm:
     sm.y = 42
 
 
+def test_frozen_field_can_be_deleted():
+    @dataclass(slots=True)
+    class Sm:
+        x: int = field(frozen=True)
+
+    sm = Sm(x=1)
+    del sm.x
+    with pytest.raises(AttributeError):
+        sm.x
+
+
 def test_plain_dataclass_is_refused():
     with pytest.raises(RuntimeError):