From 99394c90614cee6ca1b9ed919bf0345e44890dfb Mon Sep 17 00:00:00 2001
From: Mike Fogel <mike@fogel.ca>
Date: Sat, 6 Jul 2024 20:12:15 -0700
Subject: [PATCH] Change base class of TimeZoneSerializerField from DJRF's
 Field to CharField (#137)

* Add tests to clarify allow_null behavior

* Subclass CharField instead of Field

Add tests to ensure allow_null & allow_blank are working as expected

* Add test of required kwarg as well

* Add changelog entry

* Make the linter happy
---
 README.md                        |  1 +
 tests/test_serializer_field.py   | 40 ++++++++++++++++++++++++++++++++
 timezone_field/rest_framework.py |  4 ++--
 3 files changed, 43 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 8a91722..4cb1e57 100644
--- a/README.md
+++ b/README.md
@@ -148,6 +148,7 @@ poetry run pytest
   ([#57](https://github.com/mfogel/django-timezone-field/issues/57))
 - Add support for django 5.1
 - Drop support for django 3.2, 4.0, 4.1
+- Change subclass of `TimeZoneSerializerField` from DJRF's `Field` to `CharField` ([#137](https://github.com/mfogel/django-timezone-field/issues/137))
 
 #### 6.1.0 (2023-11-25)
 
diff --git a/tests/test_serializer_field.py b/tests/test_serializer_field.py
index 460f1df..48e2383 100644
--- a/tests/test_serializer_field.py
+++ b/tests/test_serializer_field.py
@@ -13,6 +13,17 @@ class _TimeZoneSerializer(serializers.Serializer):
     yield _TimeZoneSerializer
 
 
+@pytest.fixture
+def TimeZoneSerializerEmpties(use_pytz):
+    class _TimeZoneSerializer(serializers.Serializer):
+        # pylint: disable=abstract-method
+        tz_allow_null = TimeZoneSerializerField(use_pytz=use_pytz, allow_null=True)
+        tz_allow_blank = TimeZoneSerializerField(use_pytz=use_pytz, allow_blank=True)
+        tz_not_required = TimeZoneSerializerField(use_pytz=use_pytz, required=False)
+
+    yield _TimeZoneSerializer
+
+
 def test_invalid_str(TimeZoneSerializer, invalid_tz):
     serializer = TimeZoneSerializer(data={"tz": invalid_tz})
     assert not serializer.is_valid()
@@ -22,6 +33,15 @@ def test_invalid_str(TimeZoneSerializer, invalid_tz):
 def test_empty_str(TimeZoneSerializer):
     serializer = TimeZoneSerializer(data={"tz": ""})
     assert not serializer.is_valid()
+    assert serializer.data == {"tz": ""}
+    assert serializer.validated_data == {}
+
+
+def test_none(TimeZoneSerializer):
+    serializer = TimeZoneSerializer(data={"tz": None})
+    assert not serializer.is_valid()
+    assert serializer.data == {"tz": None}
+    assert serializer.validated_data == {}
 
 
 def test_valid(TimeZoneSerializer, pst, pst_tz):
@@ -41,3 +61,23 @@ def test_valid_with_timezone_object(TimeZoneSerializer, pst, pst_tz):
     assert serializer.is_valid()
     assert serializer.data["tz"] == pst
     assert serializer.validated_data["tz"] == pst_tz
+
+
+def test_valid_empties(TimeZoneSerializerEmpties):
+    serializer = TimeZoneSerializerEmpties(data={"tz_allow_null": None, "tz_allow_blank": ""})
+    assert serializer.is_valid()
+    assert serializer.data == {"tz_allow_null": None, "tz_allow_blank": ""}
+    assert serializer.validated_data == {"tz_allow_null": None, "tz_allow_blank": ""}
+
+
+def test_invalid_empties(TimeZoneSerializerEmpties):
+    serializer = TimeZoneSerializerEmpties(
+        data={
+            "tz_allow_null": "",
+            "tz_allow_blank": None,
+            "tz_not_required": None,
+        }
+    )
+    assert not serializer.is_valid()
+    assert serializer.data == {"tz_allow_null": "", "tz_allow_blank": None, "tz_not_required": None}
+    assert serializer.validated_data == {}
diff --git a/timezone_field/rest_framework.py b/timezone_field/rest_framework.py
index a75db67..92286d1 100644
--- a/timezone_field/rest_framework.py
+++ b/timezone_field/rest_framework.py
@@ -1,11 +1,11 @@
 from django.utils.encoding import force_str
 from django.utils.translation import gettext_lazy as _
-from rest_framework.fields import Field
+from rest_framework.fields import CharField
 
 from timezone_field.backends import TimeZoneNotFoundError, get_tz_backend
 
 
-class TimeZoneSerializerField(Field):
+class TimeZoneSerializerField(CharField):
     default_error_messages = {
         "invalid": _("A valid timezone is required."),
     }