[SOLVED] Marshmallow - deserializing attribute with same type as class

Marshmallow - deserializing attribute with same type as class

I'm facing some trouble using marshmallow to deserialize an object that has an attribute that is a list of object instances of itself.

I'm building a "query editor" and one of the objects I need has a list of "QueryFilters" (which will later be used to build my "WHERE" clause on the query). In the QueryFilter class I added a property that I called "nested_filters" that is a list of QueryFilter objects.

    class QueryFilterSchema(Schema):

        field_name = fields.Str()
        table = fields.Str()
        value = fields.Str()
        value_source = EnumField(ValueSource)
        comparison = EnumField(Comparison)
        operator = EnumField(BooleanOperator)
        nested_filters = fields.List(fields.Nested(__qualname__))
        nested_filter_operator = EnumField(BooleanOperator)

        def create_instance(self, data, **kwargs):
            return QueryFilter(**data)

    class ExtractorQuerySchema(Schema):

        query_language = EnumField(QueryLanguage)
        query_fields = fields.List(fields.Nested(QueryFieldSchema))
        join_sources = fields.List(fields.Nested(QueryJoinSourceSchema))
        filters = fields.List(fields.Nested(QueryFilterSchema))

        @post_load
        def create_instance(self, data, **kwargs):
            return ExtractorQuery(**data)

The only problem I'm facing is, when I deserialize an object that has nested_filters, Python deserializes the whole "filters" property as a dictionary mapping.

Of course I can implement something to convert a dict to my class attribute by attribute, but is there a more automated way to accomplish this?

Solution

Ok, the problem was way more simpler than I thought:

The code was missing the @post_load decorator above the create_instance method at QueryFilterSchema class