Move validation into more logical place

Author: jkimbo

graphql/type/definition.py

@@ -195,6 +195,9 @@ def define_field_map(type, field_map):
 
     for field_name, field in field_map.items():
         assert_valid_name(field_name)
+        assert isinstance(field, GraphQLField), (
+            '{}.{} must be an instance of GraphQLField.'.format(type, field_name)
+        )
         field_args = getattr(field, 'args', None)
 
         if field_args:

graphql/type/typemap.py

@@ -2,7 +2,7 @@
 from functools import reduce
 
 from ..utils.type_comparators import is_equal_type, is_type_sub_type_of
-from .definition import (GraphQLArgument, GraphQLField,
+from .definition import (GraphQLArgument,
                          GraphQLInputObjectField, GraphQLInputObjectType,
                          GraphQLInterfaceType, GraphQLList, GraphQLNonNull,
                          GraphQLObjectType, GraphQLUnionType, is_input_type,
@@ -87,9 +87,6 @@ def reducer(cls, map, type):
                         '{}.{} field type must be Input Type but got: {}.'.format(type, field_name, field.type)
                     )
                 else:
-                    assert isinstance(field, (GraphQLField, GraphQLField)), (
-                        '{}.{} must be an instance of GraphQLField.'.format(type, field_name)
-                    )
                     assert is_output_type(field.type), (
                         '{}.{} field type must be Output Type but got: {}.'.format(type, field_name, field.type)
                     )