Django Admin: JSONField default empty dict wont save in admin

Depending on your requirements, consider to use blank and/or null.

media_data=JSONField(blank=True, null=True)

I faced the same issue. How did I fix it? In order to bypass the validation process that excludes {} as valid json, I added both blank=True and null=True. For example: models.JSONField(blank=True, null=True, default=dict)

1. What happening. when dive into the source code. we can see the following call stack:

    1) form.is_valid() 
       ->form.full_clean()
        -->form._clean_fields()
         ---> self.cleand_data[name] = field.clean(value)
    2) field.clean(value)
        -> self.to_python(value)
        -> self.validate(value)

when look into the source code ,you can find that,it's mainly because the empty_values check.

# These values, if given to validate(), will trigger the self.required check.
EMPTY_VALUES = (None, '', [], (), {})

as you can see the empty dict {} is as an empty value for JSONField. so it will raise Error.

2. What can we do? the Solution would be to customize the models.JSONField and forms.JSONField like below.

forms.py

from django.contrib.postgres import forms

class MyJSONField(forms.JSONField):
    empty_values = [None, "", [], ()]

db/fields.py

class MyJSONField(JSONField):
    def formfield(self, **kwargs):
        from ..forms import MyJSONField

        return super().formfield(**{"form_class": MyJSONField, **kwargs})

This caused problems for me recently, though with django-mysql rather than postgres and in a custom ModelForm rather than the admin interface.

I ended up overriding my model's save() method:

from django_mysql.models import JSONField

class yourModel(model):
    media_data=JSONField(default=dict, blank=True)

    def clean(self, *args, **kwargs):
        if self.media_data is None:
            self.media_data = "{}"

    def save(self, *args, **kwargs):
        self.clean()
        super().save(*args, **kwargs)