Resolve lambda fields at runtime

graphene/core/types/base.py

@@ -5,6 +5,8 @@
 
 
 class InstanceType(object):
+    def _get_true_type(self, _type):
+        return _type() if ('function' in str(type(_type))) else _type
 
     def internal_type(self, schema):
         raise NotImplementedError("internal_type for type {} is not implemented".format(self.__class__.__name__))

graphene/core/types/definitions.py

@@ -12,13 +12,16 @@ def __init__(self, of_type, *args, **kwargs):
         self.of_type = of_type
         super(OfType, self).__init__(*args, **kwargs)
 
+    def get_type(self):
+        return self._get_true_type(self.of_type)
+
     def internal_type(self, schema):
-        return self.T(schema.T(self.of_type))
+        return self.T(schema.T(self.get_type()))
 
     def mount(self, cls):
         self.parent = cls
         if isinstance(self.of_type, MountType):
-            self.of_type.mount(cls)
+            self.get_type().mount(cls)
 
 
 class List(OfType):

graphene/core/types/field.py

@@ -80,9 +80,10 @@ def default_getter(instance, args, info):
         return default_getter
 
     def get_type(self, schema):
+        _type = self._get_true_type(self.type)
         if self.required:
-            return NonNull(self.type)
-        return self.type
+            return NonNull(_type)
+        return _type
 
     def decorate_resolver(self, resolver):
         return snake_case_args(resolver)