How to make ListField in ModelSerializer DRF not mandatory

Question

I want a field in my Django model that stores a list of strings (I don't want to use a related field for some reasons, only validate that user has sent a correct list).

I have it correctly working, the problem is that I'm not success to make this field not mandatory when updating the object via Django REST Framework.

This is my implementation, I have test some variations with the same result

class SomeModel(models.Model):
    hashtags = models.CharField(max_length=512, default=None, null=True, blank=True)

    @property
    def hashtags_as_list(self):
        """ Hashtags are stored on DB as a text json convert to object again
        """
        return json.loads(self.hashtags) if self.hashtags else None

    @hashtags_as_list.setter
    def hashtags_as_list(self, value):
        """ Hashtags are stored on DB as a text json of the list object
        """
        self.hashtags = json.dumps(value)

class SomeModelSerializer(serializers.ModelSerializer):
    hashtags = serializers.ListField(
        source='hashtags_as_list',
        default = [],
        required = False,
        child = serializers.CharField(min_length=3, max_length=32, required=False)
    )

I only get the error when I do PUT on the Browsable API, inspecting the query is sending hashtags blank.

------WebKitFormBoundary4L5MFBPrRA0QDqFL
Content-Disposition: form-data; name="hashtags"


------WebKitFormBoundary4L5MFBPrRA0QDqFL

And the error is as follows:

{
    "hashtags": [
        "This field may not be blank."
    ]
}

Answer 1

You are sending post data for hashtags except without content which is why DRF is returning that error message. You can fix that by using:

hashtags = serializers.ListField(required=False, child=CharField(allow_blank=True, ...), ...)

Please note however that you might need to adjust some of your code to handle when hashtags will normalize to empty string.