Django custom Model fields to implement PostgreSQL specific fields in SQLite

django.sqlite.fields.py

import json

from django.conf import settings
from django.contrib.postgres.fields import (
    JSONField as DjangoJSONField,
    ArrayField as DjangoArrayField,
)
from django.db.models import Field


class JSONField(DjangoJSONField):
    pass


class ArrayField(DjangoArrayField):
    pass


if 'sqlite' in settings.DATABASES['default']['ENGINE']:
    class JSONField(Field):
        def db_type(self, connection):
            return 'text'

        def from_db_value(self, value, expression, connection):
            if value is not None:
                return self.to_python(value)
            return value

        def to_python(self, value):
            if value is not None:
                try:
                    return json.loads(value)
                except (TypeError, ValueError):
                    return value
            return value

        def get_prep_value(self, value):
            if value is not None:
                return str(json.dumps(value))
            return value

        def value_to_string(self, obj):
            return self.value_from_object(obj)


    class ArrayField(JSONField):
        def __init__(self, base_field, size=None, **kwargs):
            """Care for DjanroArrayField's kwargs."""
            self.base_field = base_field
            self.size = size
            return super().__init__(**kwargs)

        def deconstruct(self):
            """Need to create migrations properly."""
            name, path, args, kwargs = super().deconstruct()
            kwargs.update({
                'base_field': self.base_field.clone(),
                'size': self.size,
            })
            return name, path, args, kwargs