Write unit-test that shows incorrect handling of overridden id field.

[BurkovBA]

Suppose that I've overridden id field on a Document with an arbitrary datatype (non-ObjectId) and created a default serializer for it:

class MyDocument(Document):
    id = StringField(primary_key=True, required=True)

class MySerializer(DocumentSerializer):
    class Meta:
        model = MyDocument

Currently, DRF-M handles this situation incorrectly. If I pass data={id: "SomeUniqueKey"} to MySerializer, it successfully stores id key-value pair in initial_data, but not in validated_data. Still, it successfully passes is_valid(), but does not create a value for id in me_data during recrusive_save() and fails mongoengine validation, when trying to create a model instance in instance = self.Meta.model(**me_data).

I have to do the following:

• [x] Write a unit-test that points to this incorrect behavior
• [ ] Fix this behavior
• [ ] Write a unit-test that points to incorrect hadling of custom id field be ReferenceFields
• [ ] Fix this behavrior

[qwiglydee]

Also, DocumentSerializer uses ReferenceField without care about type of referenced model id. It can be adjusted on class level globally, but automagic will fail.

[BurkovBA]

@qwiglydee Ah, I didn't see that, thanks for suggestion. Qwiglydee, while you're still here, I have a couple of design questions:

1. Are DynamicEmbeddedDocuments meant to work with normal EmbeddedDocumentSerializer, or should we create another specific branch in build_field(), analogous to build_nested_embedded_field(), where we'll create a specific dynamic EmbeddedDocumentSerializer subclass, as in https://github.com/umutbozkurt/django-rest-framework-mongoengine/blob/master/rest_framework_mongoengine/serializers.py#L464?
2. Do we handle extra_kwargs for fields in nested EmbeddedDocumentSerializers, that were created automatically? E.g. something like this:

class Kid(EmbeddedDocumentSerializer):
    foo = StringFIeld()

class Papa(Document):
    kid = EmbeddedDocumentField(Kid)

class PapaSerializer(DocumentSerializer):
    class Meta:
        model = Papa
        extra_kwargs={
            'kid.foo': {allow_blank: True}
        }