Fixed #12990, Refs #27694 -- Added JSONField model field.

Thanks to Adam Johnson, Carlton Gibson, Mariusz Felisiak, and Raphael
Michel for mentoring this Google Summer of Code 2019 project and
everyone else who helped with the patch.

Special thanks to Mads Jensen, Nick Pope, and Simon Charette for
extensive reviews.

Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>

tests/queries/models.py

@@ -747,3 +747,10 @@ class ReturningModel(models.Model):
 
 class NonIntegerPKReturningModel(models.Model):
     created = CreatedField(editable=False, primary_key=True)
+
+
+class JSONFieldNullable(models.Model):
+    json_field = models.JSONField(blank=True, null=True)
+
+    class Meta:
+        required_db_features = {'supports_json_field'}

tests/queries/test_bulk_update.py

@@ -3,11 +3,11 @@ import datetime
 from django.core.exceptions import FieldDoesNotExist
 from django.db.models import F
 from django.db.models.functions import Lower
-from django.test import TestCase
+from django.test import TestCase, skipUnlessDBFeature
 
 from .models import (
-    Article, CustomDbColumn, CustomPk, Detail, Individual, Member, Note,
-    Number, Order, Paragraph, SpecialCategory, Tag, Valid,
+    Article, CustomDbColumn, CustomPk, Detail, Individual, JSONFieldNullable,
+    Member, Note, Number, Order, Paragraph, SpecialCategory, Tag, Valid,
 )
 
 
@@ -228,3 +228,14 @@ class BulkUpdateTests(TestCase):
             article.created = point_in_time
         Article.objects.bulk_update(articles, ['created'])
         self.assertCountEqual(Article.objects.filter(created=point_in_time), articles)
+
+    @skipUnlessDBFeature('supports_json_field')
+    def test_json_field(self):
+        JSONFieldNullable.objects.bulk_create([
+            JSONFieldNullable(json_field={'a': i}) for i in range(10)
+        ])
+        objs = JSONFieldNullable.objects.all()
+        for obj in objs:
+            obj.json_field = {'c': obj.json_field['a'] + 1}
+        JSONFieldNullable.objects.bulk_update(objs, ['json_field'])
+        self.assertCountEqual(JSONFieldNullable.objects.filter(json_field__has_key='c'), objs)