ManyRelatedField does not seem to run validators of child relation

[dtomas]

When using a PrimaryKeyRelatedField with many=True, its validators are not run on list items.
Example:

def validate_object(obj):
    if not obj.is_valid:
        raise ValidationError("Object is not valid")

class SerializerWithManyPKField(Serializer):
    objects = PrimaryKeyRelatedField(many=True, validators=[validate_object], queryset=SomeModel.objects.all())

obj = SomeModel.objects.create(is_valid=False)
serializer = SerializerWithManyPKField(data={"objects": [obj.id]})
serializer.is_valid() # Returns `True`, does not call `validate_object`

(Using a ListField with child=PrimaryKeyRelatedField(validators=[validate_object], queryset=SomeModel.objects.all()) works, though.)

[tomchristie]

Interesting.

I can see that the ListField implementation doesn't really match up with the ManyRelatedField implementation.
I don't know if there's a good reason for that or not.

Here's ListField...

django-rest-framework/rest_framework/fields.py

Lines 1665 to 1676 in 1fd268a

	def to_internal_value(self, data):
	"""
	Dicts of native values <- Dicts of primitive datatypes.
	"""
	if html.is_html_input(data):
	data = html.parse_html_dict(data)
	if not isinstance(data, dict):
	self.fail('not_a_dict', input_type=type(data).__name__)
	if not self.allow_empty and len(data) == 0:
	self.fail('empty')
	return self.run_child_validation(data)

Which calls into run_child_validation...

django-rest-framework/rest_framework/fields.py

Lines 1684 to 1698 in 1fd268a

	def run_child_validation(self, data):
	result = {}
	errors = OrderedDict()
	for key, value in data.items():
	key = str(key)
	try:
	result[key] = self.child.run_validation(value)
	except ValidationError as e:
	errors[key] = e.detail
	if not errors:
	return result
	raise ValidationError(errors)

There's no equivalent in ManyRelatedField...

django-rest-framework/rest_framework/relations.py

Lines 520 to 529 in 1fd268a

	def to_internal_value(self, data):
	if isinstance(data, str) or not hasattr(data, '__iter__'):
	self.fail('not_a_list', input_type=type(data).__name__)
	if not self.allow_empty and len(data) == 0:
	self.fail('empty')
	return [
	self.child_relation.to_internal_value(item)
	for item in data
	]

I don't know if we're able to change this or if there's reason that'd break existing behaviour. Best I can suggest would be someone working on a pull request to bring ManyRelatedField in line with the ListField behaviour, and seeing if the test suite still passes.