Pretty print django.db.models.JSONField in Django admin?

Question

Django >= 3.1 supports a new JSONField model field. I am using one like this:

from django.db import models

class Example(models.Model):
    foobar = models.JSONField()

I've also included this model in Django's admin section. However, the field is just a simple textarea with the JSON included, not pretty printed.

How can I make sure the JSON displayed in Django's admin section is pretty printed, with indentation, like this:

{
  "example": {
     "a": 1,
     "b": 2
  }
}

Answer 1

Here is a way to indent the JSON field without additional third party packages:

import json

from django import forms
from django.contrib import admin


class PrettyJSONEncoder(json.JSONEncoder):
    def __init__(self, *args, indent, sort_keys, **kwargs):
        super().__init__(*args, indent=2, sort_keys=True, **kwargs)


class MyModelForm(forms.ModelForm):
    json_field = forms.JSONField(encoder=PrettyJSONEncoder)


class MyModelAdmin(admin.ModelAdmin):
    form = MyModelForm