Validating Values and Invocations

Conformity provides a collection of validator utilities to help you validate input against defined Conformity schemas. Which validator you employ depends on whether you want to validate inline code or validate function and method calls.

Simple Validation

When performing simple validation, you can use validate function or the field’s errors method. Consider the following schema:

person_schema = fields.Dictionary(
    {
        'name': fields.UnicodeString(),
        'height': fields.Float(gt=0),
        'age': fields.Nullable(fields.Integer(gte=0)),
        'eye_color': fields.Constant('blue', 'brown', 'black', 'green', 'yellow', 'hazel'),
    },
    optional_keys=('eye_color', ),
)

In conformity.validator there is a validate function that can validate any value against a schema and raise a ValidationError should validation fail:

>>> validate(person_schema, {'name': 'Scott', 'height': 1.9, 'age': 25, 'eye_color': 'purple'})
ValidationError: Invalid keyword arguments:
  - person.eye_color: Value is not one of: "black", "blue", "brown", "green", "hazel", "yellow"

This raises an exception when validation fails. Alternatively, you can just obtain all of the Error objects:

>>> person_schema.errors({'name': 'Scott', 'height': 1.9, 'age': 25, 'eye_color': 'purple'})
[Error(message='Value is not one of: "black", "blue", "brown", "green", "hazel", "yellow"', code='UNKNOWN', pointer='eye_color')]

Validating Function Calls

Another validation option is to globally define your schema and use Conformity’s function decorator validate_call in conformity.validator. Using the same schema as defined in the previous section, you could define a function like this:

@validate_call(fields.Dictionary({'person': person_schema}), returns=fields.Boolean())
def insert_person(person):
    return True

Invoking this function would have the following results:

>>> insert_person(person={})
ValidationError: Invalid keyword arguments:
  - person.name: Missing key: name
  - person.height: Missing key: height
  - person.age: Missing key: age
>>> insert_person(person={'name': 'Scott', 'height': 1.9, 'age': 25, 'eye_color': 'purple'})
ValidationError: Invalid keyword arguments:
  - person.eye_color: Value is not one of: "black", "blue", "brown", "green", "hazel", "yellow"
>>> insert_person(person={'name': 'Scott', 'height': 1.9, 'age': 25, 'eye_color': 'brown'})
True

One advantage of such an approach is that the return value is also validated. If insert_person had returned something other than a bool, that would have also resulted in a ValidationError. validate_call has other arguments, too:

@validate_call(args=fields.Tuple(person_schema), returns=fields.Boolean(), kwargs=None)
def insert_person(person):
    return True

In this case, the function must be called with position arguments instead of keyword arguments (kwargs=None is required to achieve this until Conformity 2.0.0). Notice that the field wrapping the person_schema is now a Tuple instead of a Dictionary, corresponding to the use of args instead of kwargs.

returns is an optional argument. If you omit it, the return value will not be validated.

Validating Method Calls

The decorator detailed in the previous section can be used only on functions unless the is_method=True is passed to the decorator, but to prevent the need for such boilerplate, conformity.validator also has a validate_method decorator:

class PersonRepository(GenericRepository):
    @validate_method(fields.Dictionary({'person': person_schema}), returns=fields.Boolean())
    def insert_person(person):
        return True

This will behave identically:

>>> repository = PersonRepository()
>>> repository.insert_person(person={})
ValidationError: Invalid keyword arguments:
  - person.name: Missing key: name
  - person.height: Missing key: height
  - person.age: Missing key: age
>>> repository.insert_person(person={'name': 'Scott', 'height': 1.9, 'age': 25, 'eye_color': 'purple'})
ValidationError: Invalid keyword arguments:
  - person.eye_color: Value is not one of: "black", "blue", "brown", "green", "hazel", "yellow"
>>> repository.insert_person(person={'name': 'Scott', 'height': 1.9, 'age': 25, 'eye_color': 'brown'})
True

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Documentation generated 2023 January 11 18:51 UTC.