Issue when trying to create use a Union type inside a converter

I was trying to write a converter function for Wagtail’s Stream Field and I run into the following error:

Exception Type: ImportError at /graphql
Exception Value: Could not import 'mysite.schema.schema' for Graphene setting 'SCHEMA'. AttributeError: 'GraphQLScalarType' object has no attribute 'graphene_type'.

Full Traceback is at the bottom. Here’s the code that throws the error:

from wagtail.wagtailcore.fields import StreamField
from graphene.types import Union, String

from graphene_django.converter import convert_django_field

class StreamFieldTypesUnion(Union):
    class Meta:
        types = (String,)


@convert_django_field.register(StreamField)
def convert_stream_field(field, registry=None):
    return StreamFieldTypesUnion()

from what I’ve understood the error happens when the schema is being created, it is trying to get the GrapheneType here: https://github.com/graphql-python/graphene/blob/master/graphene/types/typemap.py#L213

but the type not defined yet (in this case String). Is there anyway to prevent this error? I’ve tried with Dynamic without luck.

Full Traceback:

Environment:


Request Method: GET
Request URL: http://localhost:8000/graphql

Django Version: 1.11.5
Python Version: 3.6.0
Installed Applications:
['home',
 'search',
 'wagtail.wagtailforms',
 'wagtail.wagtailredirects',
 'wagtail.wagtailembeds',
 'wagtail.wagtailsites',
 'wagtail.wagtailusers',
 'wagtail.wagtailsnippets',
 'wagtail.wagtaildocs',
 'wagtail.wagtailimages',
 'wagtail.wagtailsearch',
 'wagtail.wagtailadmin',
 'wagtail.wagtailcore',
 'modelcluster',
 'taggit',
 'django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'graphene_django',
 'graphene_utils',
 'django_extensions']
Installed Middleware:
['django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware',
 'django.middleware.security.SecurityMiddleware',
 'wagtail.wagtailcore.middleware.SiteMiddleware',
 'wagtail.wagtailredirects.middleware.RedirectMiddleware']



Traceback:

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene_django/settings.py" in import_from_string
  74.         module = importlib.import_module(module_path)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/importlib/__init__.py" in import_module
  126.     return _bootstrap._gcd_import(name[level:], package, level)

File "/Users/patrick/Documents/Github/patrick91/wagtail-ql/backend/mysite/schema.py" in <module>
  15. schema = graphene.Schema(query=Query)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene/types/schema.py" in __init__
  44.         self.build_typemap()

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene/types/schema.py" in build_typemap
  105.         self._type_map = TypeMap(initial_types, auto_camelcase=self.auto_camelcase, schema=self)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene/types/typemap.py" in __init__
  66.         super(TypeMap, self).__init__(types)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphql/type/typemap.py" in __init__
  16.         self.update(reduce(self.reducer, types, OrderedDict()))

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene/types/typemap.py" in reducer
  74.             return self.graphene_reducer(map, type)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene/types/typemap.py" in graphene_reducer
  105.         return GraphQLTypeMap.reducer(map, internal_type)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphql/type/typemap.py" in reducer
  79.             field_map = type.fields

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphql/pyutils/cached_property.py" in __get__
  16.         value = obj.__dict__[self.func.__name__] = self.func(obj)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphql/type/definition.py" in fields
  180.         return define_field_map(self, self._fields)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphql/type/definition.py" in define_field_map
  189.         field_map = field_map()

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene/types/typemap.py" in construct_fields_for_type
  237.             map = self.reducer(map, field.type)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene/types/typemap.py" in reducer
  74.             return self.graphene_reducer(map, type)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene/types/typemap.py" in graphene_reducer
  80.             return self.reducer(map, type.of_type)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene/types/typemap.py" in reducer
  74.             return self.graphene_reducer(map, type)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene/types/typemap.py" in graphene_reducer
  105.         return GraphQLTypeMap.reducer(map, internal_type)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphql/type/typemap.py" in reducer
  79.             field_map = type.fields

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphql/pyutils/cached_property.py" in __get__
  16.         value = obj.__dict__[self.func.__name__] = self.func(obj)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphql/type/definition.py" in fields
  180.         return define_field_map(self, self._fields)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphql/type/definition.py" in define_field_map
  189.         field_map = field_map()

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene/types/typemap.py" in construct_fields_for_type
  237.             map = self.reducer(map, field.type)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene/types/typemap.py" in reducer
  74.             return self.graphene_reducer(map, type)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene/types/typemap.py" in graphene_reducer
  105.         return GraphQLTypeMap.reducer(map, internal_type)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphql/type/typemap.py" in reducer
  71.             for t in type.types:

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphql/pyutils/cached_property.py" in __get__
  16.         value = obj.__dict__[self.func.__name__] = self.func(obj)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphql/type/definition.py" in types
  354.         return define_types(self, self._types)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphql/type/definition.py" in define_types
  359.         types = types()

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene/types/typemap.py" in types
  215.                 assert internal_type.graphene_type == objecttype

During handling of the above exception ('GraphQLScalarType' object has no attribute 'graphene_type'), another exception occurred:

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/django/core/handlers/exception.py" in inner
  41.             response = get_response(request)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
  187.                 response = self.process_exception_by_middleware(e, request)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/django/core/handlers/base.py" in _get_response
  185.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/django/views/decorators/csrf.py" in wrapped_view
  58.         return view_func(*args, **kwargs)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/django/views/generic/base.py" in view
  62.             self = cls(**initkwargs)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene_django/views.py" in __init__
  70.             schema = graphene_settings.SCHEMA

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene_django/settings.py" in __getattr__
  116.             val = perform_import(val, attr)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene_django/settings.py" in perform_import
  60.         return import_from_string(val, setting_name)

File "/Users/patrick/.virtualenvs/wagtail-ql/lib/python3.6/site-packages/graphene_django/settings.py" in import_from_string
  78.         raise ImportError(msg)

Exception Type: ImportError at /graphql
Exception Value: Could not import 'mysite.schema.schema' for Graphene setting 'SCHEMA'. AttributeError: 'GraphQLScalarType' object has no attribute 'graphene_type'.

[zxchew2014]

@patrick91 how did u do it can show example?

[spockNinja]

Right. And since the Union is geared towards the ObjectType and not scalars, I think you’ll have better luck once you have those ObjectTypes for the blocks. You might test it out with just a few quick ones and make sure that solves the problem you’re seeing.

On Fri, Sep 15, 2017, 5:48 PM Patrick Arminio [e-mail] wrote:

Yup! I’ll create a converter for each default block.

The problem now it’s still to fix the issue that happens when trying to create the union type while creating the schema. I’ve tried with a union type that only supports strings and that didn’t work, that’s why I created the issue 😃

On Sep 16, 2017 12:35 AM, “Jacob Foster” [e-mail] wrote:

Ahh, now I see. The blocks are even more complicated than I thought from a quick glance at the StreamField.

Then at that point, I think you’ll also need an ObjectType per those block types, and those are what will go into your Union types option.

On Fri, Sep 15, 2017, 3:23 PM Patrick Arminio [e-mail] wrote:

uhm, ideally the query would be like this:

{ model { id body { … on Title { text } … on Image { mobileUlr } } } }

So allowing the clients to only fetch the information they need from the blocks 😃

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