Allow JSONField encoder customization. (#6713)

docs/api-guide/fields.md

@@ -501,9 +501,10 @@ Note that the child field **must** be an instance of `CharField`, as the hstore
 
 A field class that validates that the incoming data structure consists of valid JSON primitives. In its alternate binary mode, it will represent and validate JSON-encoded binary strings.
 
-**Signature**: `JSONField(binary)`
+**Signature**: `JSONField(binary, encoder)`
 
 - `binary` - If set to `True` then the field will output and validate a JSON encoded string, rather than a primitive data structure. Defaults to `False`.
+- `encoder` - Use this JSON encoder to serialize input object. Defaults to `None`.
 
 ---
 

rest_framework/fields.py

@@ -1746,6 +1746,7 @@ class JSONField(Field):
 
     def __init__(self, *args, **kwargs):
         self.binary = kwargs.pop('binary', False)
+        self.encoder = kwargs.pop('encoder', None)
         super().__init__(*args, **kwargs)
 
     def get_value(self, dictionary):
@@ -1767,14 +1768,14 @@ class JSONField(Field):
                     data = data.decode()
                 return json.loads(data)
             else:
-                json.dumps(data)
+                json.dumps(data, cls=self.encoder)
         except (TypeError, ValueError):
             self.fail('invalid')
         return data
 
     def to_representation(self, value):
         if self.binary:
-            value = json.dumps(value)
+            value = json.dumps(value, cls=self.encoder)
             value = value.encode()
         return value
 

rest_framework/serializers.py

@@ -1232,6 +1232,11 @@ class ModelSerializer(Serializer):
             # `allow_blank` is only valid for textual fields.
             field_kwargs.pop('allow_blank', None)
 
+        if postgres_fields and isinstance(model_field, postgres_fields.JSONField):
+            # Populate the `encoder` argument of `JSONField` instances generated
+            # for the PostgreSQL specific `JSONField`.
+            field_kwargs['encoder'] = getattr(model_field, 'encoder', None)
+
         if postgres_fields and isinstance(model_field, postgres_fields.ArrayField):
             # Populate the `child` argument on `ListField` instances generated
             # for the PostgreSQL specific `ArrayField`.

tests/test_model_serializer.py

@@ -13,6 +13,7 @@ from collections import OrderedDict
 import django
 import pytest
 from django.core.exceptions import ImproperlyConfigured
+from django.core.serializers.json import DjangoJSONEncoder
 from django.core.validators import (
     MaxValueValidator, MinLengthValidator, MinValueValidator
 )
@@ -452,15 +453,17 @@ class TestPosgresFieldsMapping(TestCase):
     def test_json_field(self):
         class JSONFieldModel(models.Model):
             json_field = postgres_fields.JSONField()
+            json_field_with_encoder = postgres_fields.JSONField(encoder=DjangoJSONEncoder)
 
         class TestSerializer(serializers.ModelSerializer):
             class Meta:
                 model = JSONFieldModel
-                fields = ['json_field']
+                fields = ['json_field', 'json_field_with_encoder']
 
         expected = dedent("""
             TestSerializer():
-                json_field = JSONField(style={'base_template': 'textarea.html'})
+                json_field = JSONField(encoder=None, style={'base_template': 'textarea.html'})
+                json_field_with_encoder = JSONField(encoder=<class 'django.core.serializers.json.DjangoJSONEncoder'>, style={'base_template': 'textarea.html'})
         """)
         self.assertEqual(repr(TestSerializer()), expected)