Django Rest framework, how to include '__all__' fields and a related field in ModelSerializer ?

Question

I have two models, one with M2M relation and a related name. I want to include all fields in the serializer and the related field.

models.py:

class Pizza(models.Model):
    name = models.CharField(max_length=50, unique=True)
    toppings = models.ManyToManyField(Topping, null=True, blank=True, related_name='pizzas')

class Topping(models.Model):
    name = models.CharField(max_length=50, unique=True)
    price = models.IntegerField(default=0)

serializer.py:

class ToppingSerializer(serializers.ModelSerializer):
    class Meta:
        model = Topping
        fields = '__all__' 

This works but it doesn't include the related field.

 fields = ['name', 'price', 'pizzas'] 

This works exactly as I want, but what happens when Toppings model has a lot of fields. I want to do something like :

fields = ['__all__', 'pizzas']

This syntax results in an error saying:

Field name __all__ is not valid for model

Is there a way to achieve the wanted behavior? Or the fields must be typed manually when using a related name ?

Answer 1

Like @DanEEStart said, DjangoRestFramework don't have a simple way to extend the 'all' value for fields, because the get_field_names methods seems to be designed to work that way.

But fortunately you can override this method to allow a simple way to include all fields and relations without enumerate a tons of fields.

I override this method like this:

class ToppingSerializer(serializers.ModelSerializer):

    class Meta:
        model = Topping
        fields = '__all__'
        extra_fields = ['pizzas']

    def get_field_names(self, declared_fields, info):
        expanded_fields = super(ToppingSerializer, self).get_field_names(declared_fields, info)

        if getattr(self.Meta, 'extra_fields', None):
            return expanded_fields + self.Meta.extra_fields
        else:
            return expanded_fields

Note that this method only change the behaviour of this serializer, and the extra_fields attribute only works on this serializer class.

If you have a tons of serializer like this, you can create a intermediate class to include this get_fields_names method in one place and reuse'em many times. Some like this:

class CustomSerializer(serializers.HyperlinkedModelSerializer):

    def get_field_names(self, declared_fields, info):
        expanded_fields = super(CustomSerializer, self).get_field_names(declared_fields, info)

        if getattr(self.Meta, 'extra_fields', None):
            return expanded_fields + self.Meta.extra_fields
        else:
            return expanded_fields


class ToppingSerializer(CustomSerializer):

    class Meta:
        model = Topping
        fields = '__all__'
        extra_fields = ['pizzas']

class AnotherSerializer(CustomSerializer):

    class Meta:
        model = Post
        fields = '__all__'
        extra_fields = ['comments']