Implemented None Check for all type of reference and list of reference field.

Author: Arun S Kumar

graphene_mongo/converter.py

@@ -121,24 +121,26 @@ def get_reference_objects(*args, **kwargs):
             def reference_resolver(root, *args, **kwargs):
                 choice_to_resolve = dict()
                 to_resolve = getattr(root, field.name or field.db_name)
-                for each in to_resolve:
-                    if each['_cls'] not in choice_to_resolve:
-                        choice_to_resolve[each['_cls']] = list()
-                    choice_to_resolve[each['_cls']].append(each["_ref"].id)
-
-                pool = ThreadPoolExecutor(5)
-                futures = list()
-                for model, object_id_list in choice_to_resolve.items():
-                    futures.append(pool.submit(get_reference_objects, (model, object_id_list, registry, args)))
-                result = list()
-                for x in as_completed(futures):
-                    result += x.result()
-                to_resolve_object_ids = [each["_ref"].id for each in to_resolve]
-                result_to_resolve_object_ids = [each.id for each in result]
-                ordered_result = list()
-                for each in to_resolve_object_ids:
-                    ordered_result.append(result[result_to_resolve_object_ids.index(each)])
-                return ordered_result
+                if to_resolve:
+                    for each in to_resolve:
+                        if each['_cls'] not in choice_to_resolve:
+                            choice_to_resolve[each['_cls']] = list()
+                        choice_to_resolve[each['_cls']].append(each["_ref"].id)
+
+                    pool = ThreadPoolExecutor(5)
+                    futures = list()
+                    for model, object_id_list in choice_to_resolve.items():
+                        futures.append(pool.submit(get_reference_objects, (model, object_id_list, registry, args)))
+                    result = list()
+                    for x in as_completed(futures):
+                        result += x.result()
+                    to_resolve_object_ids = [each["_ref"].id for each in to_resolve]
+                    result_to_resolve_object_ids = [each.id for each in result]
+                    ordered_result = list()
+                    for each in to_resolve_object_ids:
+                        ordered_result.append(result[result_to_resolve_object_ids.index(each)])
+                    return ordered_result
+                return []
 
             return graphene.List(
                 base_type._type,
@@ -206,15 +208,17 @@ def convert_field_to_union(field, registry=None):
 
     def reference_resolver(root, *args, **kwargs):
         dereferenced = getattr(root, field.name or field.db_name)
-        document = get_document(dereferenced["_cls"])
-        document_field = mongoengine.ReferenceField(document)
-        document_field = convert_mongoengine_field(document_field, registry)
-        _type = document_field.get_type().type
-        only_fields = _type._meta.only_fields.split(",") if isinstance(_type._meta.only_fields,
-                                                                       str) else list()
-        return document.objects().no_dereference().only(*list(
-            set(only_fields + [to_snake_case(i) for i in get_query_fields(args[0])[_type._meta.name].keys()]))).get(
-            pk=dereferenced["_ref"].id)
+        if dereferenced:
+            document = get_document(dereferenced["_cls"])
+            document_field = mongoengine.ReferenceField(document)
+            document_field = convert_mongoengine_field(document_field, registry)
+            _type = document_field.get_type().type
+            only_fields = _type._meta.only_fields.split(",") if isinstance(_type._meta.only_fields,
+                                                                           str) else list()
+            return document.objects().no_dereference().only(*list(
+                set(only_fields + [to_snake_case(i) for i in get_query_fields(args[0])[_type._meta.name].keys()]))).get(
+                pk=dereferenced["_ref"].id)
+        return None
 
     if isinstance(field, mongoengine.GenericReferenceField):
         return graphene.Field(_union, resolver=reference_resolver,
@@ -241,13 +245,15 @@ def reference_resolver(root, *args, **kwargs):
         return None
 
     def cached_reference_resolver(root, *args, **kwargs):
-        _type = registry.get_type_for_model(field.document_type)
-        only_fields = _type._meta.only_fields.split(",") if isinstance(_type._meta.only_fields,
-                                                                       str) else list()
-        return field.document_type.objects().no_dereference().only(
-            *(list(set(only_fields + [to_snake_case(i) for i in get_query_fields(args[0]).keys()]))
-              )).get(
-            pk=getattr(root, field.name or field.db_name))
+        if field:
+            _type = registry.get_type_for_model(field.document_type)
+            only_fields = _type._meta.only_fields.split(",") if isinstance(_type._meta.only_fields,
+                                                                           str) else list()
+            return field.document_type.objects().no_dereference().only(
+                *(list(set(only_fields + [to_snake_case(i) for i in get_query_fields(args[0]).keys()]))
+                  )).get(
+                pk=getattr(root, field.name or field.db_name))
+        return None
 
     def dynamic_type():
         _type = registry.get_type_for_model(model)
@@ -271,12 +277,14 @@ def convert_lazy_field_to_dynamic(field, registry=None):
 
     def lazy_resolver(root, *args, **kwargs):
         document = getattr(root, field.name or field.db_name)
-        _type = registry.get_type_for_model(document.document_type)
-        only_fields = _type._meta.only_fields.split(",") if isinstance(_type._meta.only_fields,
-                                                                       str) else list()
-        return document.document_type.objects().no_dereference().only(
-            *(list(set((only_fields + [to_snake_case(i) for i in get_query_fields(args[0]).keys()]))))).get(
-            pk=document.pk)
+        if document:
+            _type = registry.get_type_for_model(document.document_type)
+            only_fields = _type._meta.only_fields.split(",") if isinstance(_type._meta.only_fields,
+                                                                           str) else list()
+            return document.document_type.objects().no_dereference().only(
+                *(list(set((only_fields + [to_snake_case(i) for i in get_query_fields(args[0]).keys()]))))).get(
+                pk=document.pk)
+        return None
 
     def dynamic_type():
         _type = registry.get_type_for_model(model)