JSONField cannot process empty value from html form on browsable API

[giff-h]

Given this example setup:

example/models.py

from django.db import models

class EmptyJson(models.Model):
    basic = models.JSONField()
    allow_blank = models.JSONField(blank=True)
    has_default = models.JSONField(default=dict)

example/views.py

from rest_framework import permissions, serializers, viewsets
from example.models import EmptyJson

class EmptyJsonSerializer(serializers.HyperlinkedModelSerializer):
    class Meta:
        model = EmptyJson
        fields = '__all__'

class EmptyJsonViewSet(viewsets.ModelViewSet):
    serializer_class = EmptyJsonSerializer
    queryset = EmptyJson.objects.order_by('id')
    permission_classes = [permissions.AllowAny]

example/urls.py

from django.urls import path, include
from rest_framework import routers

from example.views import EmptyJsonViewSet

router = routers.DefaultRouter()
router.register('example', EmptyJsonViewSet)

urlpatterns = [
    path('', include(router.urls)),
]

Navigate to it and everything looks good

Clear the fields, POST, and it returns 400.

After stepping through the code in a debugger, it appears that it's interpreting the empty string input as a JSON string, and obviously it'll be invalid. field_value = '""' is valid JSON empty string, field_value = '' is invalid JSON. IMO it should be interpreting empty string field values as literally empty to align with expectations of HTML forms.

I present this as a possible fix. Obviously tests should be added to cover various cases and prevent regression, but this is what currently exists:

rest_framework/fields.py

...

class JSONField(Field):
    ...

    def get_value(self, dictionary):
        if html.is_html_input(dictionary) and self.field_name in dictionary:
            # When HTML form input is used, mark up the input
            # as being a JSON string, rather than a JSON primitive.
            class JSONString(str):
                def __new__(cls, value):
                    ret = str.__new__(cls, value)
                    ret.is_json_string = True
                    return ret
            return JSONString(dictionary[self.field_name])
        return dictionary.get(self.field_name, empty)

This is what I'm thinking of:

    def get_value(self, dictionary):
        if html.is_html_input(dictionary) and self.field_name in dictionary:
            if dictionary[self.field_name] == '':  # could possibly trim first
                return empty
            ...