deb-python-jsonschema/docs/creating.rst

Creating or Extending Validators

jsonschema.validators

create

Create a new validator (class).

argument dict meta_schema

the meta schema for the new validator class

argument dict validators

a mapping from validator names to functions that validate the given name. Each function should take 4 arguments: a validator instance, the value of the current validator property in the instance being validated, the instance, and the schema.

argument str version

an identifier for the version that this validator will validate. If provided, the returned validator class will have its __name__ set to include the version, and also will have validates automatically called for the given version.

argument dict default_types

a default mapping to use for instances of the validator when mapping between JSON types to Python types. The default for this argument is probably fine. Instances of the returned validator can still have their types customized on a per-instance basis.

returns

a new jsonschema.IValidator class

extend

Create a new validator that extends an existing validator class.

argument jsonschema.IValidator validator

an existing validator class

argument dict validators

a set of new validators to add to the new validator.

Note

Any validators with the same name as an existing one will (silently) replace the old validator entirely.

If you wish to extend an old validator, call it directly in the replacing validator function by retrieving it using OldValidator.VALIDATORS["the validator"].

argument str version

a version for the new validator

returns

a new jsonschema.IValidator class

Note

Meta Schemas

The new validator will just keep the old validator's meta schema.

If you wish to change or extend the meta schema in the new validator, modify META_SCHEMA directly on the returned class.

The meta schema on the new validator will not be a copy, so you'll probably want to copy it before modifying it to not affect the old validator.

validator_for

Retrieve the validator appropriate for validating the given schema.

Uses the $schema property that should be present in the given schema to look up the appropriate validator.

argument schema

the schema to look at

argument default

the default to return if the appropriate validator cannot be determined. If unprovided, the default will be to just return Draft4Validator

validates

Creating Validation Errors

Any validating function that validates against a subschema should call ValidatorMixin.descend, rather than ValidatorMixin.iter_errors. If it recurses into the instance, or schema, it should pass one or both of the path or schema_path arguments to ValidatorMixin.descend in order to properly maintain where in the instance or schema respsectively the error occurred.