Bug when flattening with a non-existent sequence and colander.drop

[iwillau]

Bug when flattening with a non-existent sequence and colander.drop

[fmigneault]

For anyone interested about an "easy" solution to handle this, my solution was to insert the following definitions to drop the mapping and sequences with minimal code refactoring when missing=drop.

from colander import MappingSchema as MapSchema, SequenceSchema as SeqSchema

class DropableSchema(colander.SchemaNode):
    def deserialize(self, cstruct):
        if self.default is colander.null and self.missing is colander.drop and cstruct is None:
            return colander.drop
        return super(DropableSchema, self).deserialize(cstruct)

class MappingSchema(DropableSchema, MapSchema):
    """Override the default :class:`colander.MappingSchema` to auto-handle dropping missing definition as required."""


class SequenceSchema(DropableSchema, SeqSchema):
    """Override the default :class:`colander.SequenceSchema` to auto-handle dropping missing definition as required."""

Following will then resolve as expected by dropping the missing s1 definition:

class SchemaA(MappingSchema):
    field = SchemaNode(String())

class SchemaB(MappingSchema):
    s1 = SchemaA(missing=drop)   # optional
    s2 = SchemaA()               # required

SchemaB().deserialize({"s1": {"field": "ok"}, "s2": {"field": "ok"}})
# {'s1': {'field': 'ok'}, 's2': {'field': 'ok'}}
SchemaB().deserialize({"s1": None, "s2": {"field": "ok"}})   # this would raise normally
# {'s2': {'field': 'ok'}}
SchemaB().deserialize({"s2": {"field": "ok"}})
# {'s2': {'field': 'ok'}}