feat: enforce Decimal type in min_value and max_value arguments of DecimalField (#8972)

* add warning when min_value and max_value are not decimal

* remove redundant module name in log

---------

Co-authored-by: ismaeljs <>

Author: IsmaelJS

rest_framework/fields.py

@@ -4,6 +4,7 @@
 import decimal
 import functools
 import inspect
+import logging
 import re
 import uuid
 from collections.abc import Mapping
@@ -38,6 +39,8 @@
 from rest_framework.utils.timezone import valid_datetime
 from rest_framework.validators import ProhibitSurrogateCharactersValidator
 
+logger = logging.getLogger("rest_framework.fields")
+
 
 class empty:
     """
@@ -990,6 +993,11 @@ def __init__(self, max_digits, decimal_places, coerce_to_string=None, max_value=
         self.max_value = max_value
         self.min_value = min_value
 
+        if self.max_value is not None and not isinstance(self.max_value, decimal.Decimal):
+            logger.warning("max_value in DecimalField should be Decimal type.")
+        if self.min_value is not None and not isinstance(self.min_value, decimal.Decimal):
+            logger.warning("min_value in DecimalField should be Decimal type.")
+
         if self.max_digits is not None and self.decimal_places is not None:
             self.max_whole_digits = self.max_digits - self.decimal_places
         else:

tests/test_fields.py

@@ -1216,6 +1216,17 @@ class TestMinMaxDecimalField(FieldValues):
         min_value=10, max_value=20
     )
 
+    def test_warning_when_not_decimal_types(self, caplog):
+        import logging
+        serializers.DecimalField(
+            max_digits=3, decimal_places=1,
+            min_value=10, max_value=20
+        )
+        assert caplog.record_tuples == [
+            ("rest_framework.fields", logging.WARNING, "max_value in DecimalField should be Decimal type."),
+            ("rest_framework.fields", logging.WARNING, "min_value in DecimalField should be Decimal type.")
+        ]
+
 
 class TestAllowEmptyStrDecimalFieldWithValidators(FieldValues):
     """