paylogic / halogen Goto Github PK

Given these schema

class ChildSchema(halogen.Schema):
    some_other_field = halogen.Attr(halogen.types.String())

class ParentSchema(halogen.Schema):
    some_field = halogen.Attr(ChildSchema)

To make some_field nullable during deserialization, I have to create a deserialize class method on ChildSchema:

class ChildSchema(halogen.Schema):
    some_other_field = halogen.Attr(halogen.types.String())

    @classmethod
    def deserialize(self, value, **kwargs):
        return None if value is None else super().deserialize(value)

It would be nice if halogen.Attr supported a nullable parameter:
some_field = halogen.Attr(ChildSchema, nullable=True)

Or alternatively support wrapping:
some_field = halogen.Attr(halogen.Nullable(ChildSchema))

I'm trying to deserialize an object which occasionally may contain a field. If the field is not present, I want to use a default value to deserialize the object.

If in the schema I use just the default value, during deserialization a validation error raises. If is use occasional = halogen.Attr(required=False, default="custom"), the deserialization works but the field occasional field is not populated with "custom" value.

Haven't thought about how this might be done, but it would be very nice if there was a way to control the order of fields when the HAL document is created/rendered.

Looking through the code it appears curies are initially constructed as a set() but subsequently converted to a plain list(). Therefore the order of curies is randomised.

This not only seems at odds with the expected behaviour of a list (or list-like) structure, but means tests become more complex --- having to convert the actual, and expected output to compare curies as sets is painful.

Perhaps this is more of an edge case, but would the developers be willing to discuss this possibility?

When implementing collection endpoints with paging support, the _link relations usually have next and prev links. A corresponding schema for a user collection could be something like

class UserCollectionSchema(Schema):

  self = halogen.Link(attr=lambda u: f"url?page={u.page}")
  next = halogen.Link(attr=lambda u: f"url?page={u.page + 1}")
  prev = halogen.Link(attr=lambda u: f"url?page={u.page - 1}")

  users = halogen.Embedded(halogen.types.List(UserSchema), attr=...)

Is it possible to only serialize/render the next and prev links only when a certain condition is met, e.g. when there is actually a next or a previous page?

Schema's are hierarchical, but we need to come up with somewhat more usable data structure than what ValidationError.to_dict() returns. It should be easy to associate the error with the field of the web form.