feat: Allow serializer customization for JSONField (#53)

annoying/decorators.py

@@ -136,6 +136,7 @@ def wrapper(**kwargs):
     def register_signal(self, signal, name):
         self._signals[name] = signal
 
+
 signals = Signals()
 
 

annoying/fields.py

@@ -2,6 +2,7 @@
 
 from django.db import models
 from django.db.models import OneToOneField
+from django.db.models.fields import NOT_PROVIDED
 from django.db.transaction import atomic
 from django.core.serializers.json import DjangoJSONEncoder
 try:
@@ -55,6 +56,11 @@ class JSONField(models.TextField):
     JSON objects seamlessly.
     Django snippet #1478
 
+    Custom serializer/deserializer functions can be used to customize field's behavior.
+    Defaults:
+     - serializer: json.dumps(value, cls=DjangoJSONEncoder, sort_keys=True, indent=2, separators=(',', ': '))
+     - deserializer: json.loads(value)
+
     example:
         class Page(models.Model):
             data = JSONField(blank=True, null=True)
@@ -65,6 +71,21 @@ class Page(models.Model):
         page.save()
     """
 
+    def __init__(self, *args, **kwargs):
+        def dumps(value):
+            return json.dumps(value, cls=DjangoJSONEncoder, sort_keys=True, indent=2, separators=(',', ': '))
+
+        self.serializer = kwargs.pop('serializer', dumps)
+        self.deserializer = kwargs.pop('deserializer', json.loads)
+
+        super(JSONField, self).__init__(*args, **kwargs)
+
+    def deconstruct(self):
+        name, path, args, kwargs = super(JSONField, self).deconstruct()
+        kwargs['serializer'] = self.serializer
+        kwargs['deserializer'] = self.deserializer
+        return name, path, args, kwargs
+
     def to_python(self, value):
         """
         Convert a string from the database to a Python value.
@@ -74,9 +95,9 @@ def to_python(self, value):
 
         try:
             if isinstance(value, six.string_types):
-                return json.loads(value)
+                return self.deserializer(value)
             elif isinstance(value, bytes):
-                return json.loads(value.decode('utf8'))
+                return self.deserializer(value.decode('utf8'))
         except ValueError:
             pass
         return value
@@ -88,7 +109,7 @@ def get_prep_value(self, value):
         if value == "":
             return None
         if isinstance(value, dict) or isinstance(value, list):
-            return json.dumps(value, cls=DjangoJSONEncoder, sort_keys=True, indent=2, separators=(',', ': '))
+            return self.serializer(value)
         return super(JSONField, self).get_prep_value(value)
 
     def from_db_value(self, value, *args, **kwargs):
@@ -106,12 +127,12 @@ def get_db_prep_save(self, value, *args, **kwargs):
         if value == "":
             return None
         if isinstance(value, dict) or isinstance(value, list):
-            return json.dumps(value, cls=DjangoJSONEncoder, sort_keys=True, indent=2, separators=(',', ': '))
+            return self.serializer(value)
         else:
             return super(JSONField, self).get_db_prep_save(value, *args, **kwargs)
 
     def value_from_object(self, obj):
         value = super(JSONField, self).value_from_object(obj)
         if self.null and value is None:
             return None
-        return json.dumps(value, sort_keys=True, indent=2, separators=(',', ': '))
+        return self.serializer(value)

setup.py

@@ -1,6 +1,6 @@
 from annoying import __version__
 
-from setuptools import setup, find_packages
+from setuptools import setup
 setup(
     name="django-annoying",
     version=__version__,

tests/models.py

@@ -1,4 +1,7 @@
+from json import loads, dumps
+
 from django.db import models
+
 from annoying.fields import AutoOneToOneField
 from annoying.fields import JSONField
 
@@ -8,6 +11,15 @@ class SuperVillain(models.Model):
     stats = JSONField(default=None, blank=True, null=True)
 
 
+class Minion(models.Model):
+    _PREFIX = 'I can: '
+
+    name = models.CharField(max_length="20", default="Igor")
+    skills = JSONField(default=None, blank=True, null=True,
+                       serializer=lambda value: '{0}{1}'.format(Minion._PREFIX, dumps(value)),
+                       deserializer=lambda value: loads(value[len(Minion._PREFIX):]))
+
+
 class SuperHero(models.Model):
     name = models.CharField(max_length="20", default="Captain Hammer")
     mortal_enemy = AutoOneToOneField(SuperVillain, on_delete=models.CASCADE, related_name='mortal_enemy')

tests/test_decorators.py

@@ -2,7 +2,7 @@
 
 import json
 
-from django.test import TestCase, override_settings
+from django.test import TestCase
 
 
 class AJAXRequestTestCase(TestCase):

tests/test_fields.py

@@ -1,6 +1,7 @@
 import json
 
 from django.test import TestCase
+
 from . import models
 
 
@@ -26,8 +27,8 @@ def test_json_field_create(self):
         # Refresh from DB
         super_villain = models.SuperVillain.objects.get(pk=sv.pk)
 
-        self.assertEqual(super_villain.stats['strength'], 100)
-        self.assertEqual(super_villain.stats['defence'], 50)
+        self.assertEqual(super_villain.stats['strength'], stats['strength'])
+        self.assertEqual(super_villain.stats['defence'], stats['defence'])
         self.assertEqual(dump_dict(super_villain.stats), dump_dict(stats))
 
     def test_json_field_update(self):
@@ -42,6 +43,20 @@ def test_json_field_update(self):
         # Refresh from DB
         super_villain = models.SuperVillain.objects.get(pk=super_villain.pk)
 
-        self.assertEqual(super_villain.stats['strength'], 100)
-        self.assertEqual(super_villain.stats['defence'], 50)
+        self.assertEqual(super_villain.stats['strength'], stats['strength'])
+        self.assertEqual(super_villain.stats['defence'], stats['defence'])
         self.assertEqual(dump_dict(super_villain.stats), dump_dict(stats))
+
+    def test_json_field_custom_serializer_deserializer(self):
+        skills = {
+            'make': ['atomic_bomb', 'coffee'],
+            'understand': ['string_theory', 'women'],
+        }
+        minion = models.Minion.objects.create(skills=skills)
+
+        # Refresh from DB
+        minion = models.Minion.objects.get(pk=minion.pk)
+
+        self.assertEqual(minion.skills['make'], skills['make'])
+        self.assertEqual(minion.skills['understand'], skills['understand'])
+        self.assertEqual(dump_dict(minion.skills), dump_dict(skills))