SerializerMutation nested serializer with many=True

[sks-keo]

I have a DRF Serializer with a field using a custom nested serializer, something like this:

class FirstSerializer(serializers.ModelSerializer):
    class Meta:
        model = FirstModel
        fields = "all"

class SecondSerializer(serializers.ModelSerializer):
    class Meta:
        model = SecondModel
        fields = ('field_a', 'field_b')
    field_b = FirstSerializer(many=True)

I'm trying to create a mutation on the FirstSerializer like this:

class MyMutation(SerializerMutation):
    class Meta:
        serializer_class = SecondSerializer

djangorestframework==3.8.2

graphene>=2.1.2
graphene-django==2.1rc1
graphql-core>=2.1rc1

[trixn86]

I observed the same problem when trying to use nested Serializers in a SerializerMutation.

djangorestframework==3.8.2
graphene==2.1.3
graphene-django==2.1.0
graphql-core>=2.1

[trixn86]

After debugging for a while I found that the reason was there was no type defined for the model of the serializers.

The SerializerMutation tries to define an output type from the model of a serializer. If no DjangoObjectType exists for that model it will silently return None as the type. This will later lead to an error.

Actually I would like to see a SerializerMutation that does not require model types to be defined. I don't overall like very much, that the whole library is very tightly coupled with the django ORM. There is also a need for not exposing every model field one to one to the outside world. A schema should be decoupled from the ORM because it should reflect the needs of the client to fetch data.

[p02diada]

I have the same problem but without using many=true. How did you solve your problem? I have defined an DjangoObjectType for my model but it does not work yet.

[zbyte64]

Trying to construct a unit test to reproduce this, here is what I got:

def test_construct_mutate_nested_model():
    class ChildSerializer(serializers.ModelSerializer):
        class Meta:
            model = MyFakeModel
            fields = "__all__"

    class ParentSerializer(serializers.ModelSerializer):
        child = ChildSerializer(many=True)

        class Meta:
            model = MyFakeModel
            fields = "__all__"

    class MyMutation(SerializerMutation):
        class Meta:
            serializer_class = ParentSerializer

This seems to work fine though.

[dopeboy]

@sks-keo, did you reach a solution?

[coler-j]

@dopeboy can you please re-open this? I am currently encountering a variation of it. The error I am getting is:

File "/...../graphql/execution/executor.py", line 590, in complete_list_value
    assert isinstance(result, Iterable), (
AssertionError: User Error: expected iterable, but did not find one for field MyFieldMutationPayload.mappings.