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validators.py
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""" Creation and extension of validators, with implementations for existing drafts. """ from __future__ import division from warnings import warn import contextlib import json import numbers from six import add_metaclass from jsonschema import ( _legacy_validators, _types, _utils, _validators, exceptions, ) from jsonschema.compat import ( Sequence, int_types, iteritems, lru_cache, str_types, unquote, urldefrag, urljoin, urlopen, urlsplit, ) # Sigh. https://gitlab.com/pycqa/flake8/issues/280 # https://github.com/pyga/ebb-lint/issues/7 # Imported for backwards compatibility. from jsonschema.exceptions import ErrorTree ErrorTree class _DontDoThat(Exception): """ Raised when a Validators with non-default type checker is misused. Asking one for DEFAULT_TYPES doesn't make sense, since type checkers exist for the unrepresentable cases where DEFAULT_TYPES can't represent the type relationship. """ def __str__(self): return "DEFAULT_TYPES cannot be used on Validators using TypeCheckers" validators = {} meta_schemas = _utils.URIDict() def _generate_legacy_type_checks(types=()): """ Generate newer-style type checks out of JSON-type-name-to-type mappings. Arguments: types (dict): A mapping of type names to their Python types Returns: A dictionary of definitions to pass to `TypeChecker` """ types = dict(types) def gen_type_check(pytypes): pytypes = _utils.flatten(pytypes) def type_check(checker, instance): if isinstance(instance, bool): if bool not in pytypes: return False return isinstance(instance, pytypes) return type_check definitions = {} for typename, pytypes in iteritems(types): definitions[typename] = gen_type_check(pytypes) return definitions _DEPRECATED_DEFAULT_TYPES = { u"array": list, u"boolean": bool, u"integer": int_types, u"null": type(None), u"number": numbers.Number, u"object": dict, u"string": str_types, } _TYPE_CHECKER_FOR_DEPRECATED_DEFAULT_TYPES = _types.TypeChecker( type_checkers=_generate_legacy_type_checks(_DEPRECATED_DEFAULT_TYPES), ) def validates(version): """ Register the decorated validator for a ``version`` of the specification. Registered validators and their meta schemas will be considered when parsing ``$schema`` properties' URIs. Arguments: version (str): An identifier to use as the version's name Returns: collections.Callable: a class decorator to decorate the validator with the version """ def _validates(cls): validators[version] = cls meta_schema_id = cls.ID_OF(cls.META_SCHEMA) if meta_schema_id: meta_schemas[meta_schema_id] = cls return cls return _validates def _DEFAULT_TYPES(self): if self._CREATED_WITH_DEFAULT_TYPES is None: raise _DontDoThat() warn( ( "The DEFAULT_TYPES attribute is deprecated. " "See the type checker attached to this validator instead." ), DeprecationWarning, stacklevel=2, ) return self._DEFAULT_TYPES class _DefaultTypesDeprecatingMetaClass(type): DEFAULT_TYPES = property(_DEFAULT_TYPES) def _id_of(schema): if schema is True or schema is False: return u"" return schema.get(u"$id", u"") def create( meta_schema, validators=(), version=None, default_types=None, type_checker=None, id_of=_id_of, ): """ Create a new validator class. Arguments: meta_schema (collections.Mapping): the meta schema for the new validator class validators (collections.Mapping): a mapping from names to callables, where each callable will validate the schema property with the given name. Each callable should take 4 arguments: 1. a validator instance, 2. the value of the property being validated within the instance 3. the instance 4. the schema version (str): an identifier for the version that this validator class will validate. If provided, the returned validator class will have its ``__name__`` set to include the version, and also will have `jsonschema.validators.validates` automatically called for the given version. type_checker (jsonschema.TypeChecker): a type checker, used when applying the :validator:`type` validator. If unprovided, a `jsonschema.TypeChecker` will be created with a set of default types typical of JSON Schema drafts. default_types (collections.Mapping): .. deprecated:: 3.0.0 Please use the type_checker argument instead. If set, it provides mappings of JSON types to Python types that will be converted to functions and redefined in this object's `jsonschema.TypeChecker`. id_of (collections.Callable): A function that given a schema, returns its ID. Returns: a new `jsonschema.IValidator` class """ if default_types is not None: if type_checker is not None: raise TypeError( "Do not specify default_types when providing a type checker.", ) _created_with_default_types = True warn( ( "The default_types argument is deprecated. " "Use the type_checker argument instead." ), DeprecationWarning, stacklevel=2, ) type_checker = _types.TypeChecker( type_checkers=_generate_legacy_type_checks(default_types), ) else: default_types = _DEPRECATED_DEFAULT_TYPES if type_checker is None: _created_with_default_types = False type_checker = _TYPE_CHECKER_FOR_DEPRECATED_DEFAULT_TYPES elif type_checker is _TYPE_CHECKER_FOR_DEPRECATED_DEFAULT_TYPES: _created_with_default_types = False else: _created_with_default_types = None @add_metaclass(_DefaultTypesDeprecatingMetaClass) class Validator(object): VALIDATORS = dict(validators) META_SCHEMA = dict(meta_schema) TYPE_CHECKER = type_checker ID_OF = staticmethod(id_of) DEFAULT_TYPES = property(_DEFAULT_TYPES) _DEFAULT_TYPES = dict(default_types) _CREATED_WITH_DEFAULT_TYPES = _created_with_default_types def __init__( self, schema, types=(), resolver=None, format_checker=None, ): if types: warn( ( "The types argument is deprecated. Provide " "a type_checker to jsonschema.validators.extend " "instead." ), DeprecationWarning, stacklevel=2, ) self.TYPE_CHECKER = self.TYPE_CHECKER.redefine_many( _generate_legacy_type_checks(types), ) if resolver is None: resolver = RefResolver.from_schema(schema, id_of=id_of) self.resolver = resolver self.format_checker = format_checker self.schema = schema @classmethod def check_schema(cls, schema): for error in cls(cls.META_SCHEMA).iter_errors(schema): raise exceptions.SchemaError.create_from(error) def iter_errors(self, instance, _schema=None): if _schema is None: _schema = self.schema if _schema is True: return elif _schema is False: yield exceptions.ValidationError( "False schema does not allow %r" % (instance,), validator=None, validator_value=None, instance=instance, schema=_schema, ) return scope = id_of(_schema) if scope: self.resolver.push_scope(scope) try: ref = _schema.get(u"$ref") if ref is not None: validators = [(u"$ref", ref)] else: validators = iteritems(_schema) for k, v in validators: validator = self.VALIDATORS.get(k) if validator is None: continue errors = validator(self, v, instance, _schema) or () for error in errors: # set details if not already set by the called fn error._set( validator=k, validator_value=v, instance=instance, schema=_schema, ) if k != u"$ref": error.schema_path.appendleft(k) yield error finally: if scope: self.resolver.pop_scope() def descend(self, instance, schema, path=None, schema_path=None): for error in self.iter_errors(instance, schema): if path is not None: error.path.appendleft(path) if schema_path is not None: error.schema_path.appendleft(schema_path) yield error def validate(self, *args, **kwargs): for error in self.iter_errors(*args, **kwargs): raise error def is_type(self, instance, type): try: return self.TYPE_CHECKER.is_type(instance, type) except exceptions.UndefinedTypeCheck: raise exceptions.UnknownType(type, instance, self.schema) def is_valid(self, instance, _schema=None): error = next(self.iter_errors(instance, _schema), None) return error is None if version is not None: Validator = validates(version)(Validator) Validator.__name__ = version.title().replace(" ", "") + "Validator" return Validator def extend(validator, validators=(), version=None, type_checker=None): """ Create a new validator class by extending an existing one. Arguments: validator (jsonschema.IValidator): an existing validator class validators (collections.Mapping): a mapping of new validator callables to extend with, whose structure is as in `create`. .. note:: Any validator callables with the same name as an existing one will (silently) replace the old validator callable entirely, effectively overriding any validation done in the "parent" validator class. If you wish to instead extend the behavior of a parent's validator callable, delegate and call it directly in the new validator function by retrieving it using ``OldValidator.VALIDATORS["validator_name"]``. version (str): a version for the new validator class type_checker (jsonschema.TypeChecker): a type checker, used when applying the :validator:`type` validator. If unprovided, the type checker of the extended `jsonschema.IValidator` will be carried along.` Returns: a new `jsonschema.IValidator` class extending the one provided .. note:: Meta Schemas The new validator class will have its parent's meta schema. If you wish to change or extend the meta schema in the new validator class, modify ``META_SCHEMA`` directly on the returned class. Note that no implicit copying is done, so a copy should likely be made before modifying it, in order to not affect the old validator. """ all_validators = dict(validator.VALIDATORS) all_validators.update(validators) if type_checker is None: type_checker = validator.TYPE_CHECKER elif validator._CREATED_WITH_DEFAULT_TYPES: raise TypeError( "Cannot extend a validator created with default_types " "with a type_checker. Update the validator to use a " "type_checker when created." ) return create( meta_schema=validator.META_SCHEMA, validators=all_validators, version=version, type_checker=type_checker, id_of=validator.ID_OF, ) Draft3Validator = create( meta_schema=_utils.load_schema("draft3"), validators={ u"$ref": _validators.ref, u"additionalItems": _validators.additionalItems, u"additionalProperties": _validators.additionalProperties, u"dependencies": _legacy_validators.dependencies_draft3, u"disallow": _legacy_validators.disallow_draft3, u"divisibleBy": _validators.multipleOf, u"enum": _validators.enum, u"extends": _legacy_validators.extends_draft3, u"format": _validators.format, u"items": _legacy_validators.items_draft3_draft4, u"maxItems": _validators.maxItems, u"maxLength": _validators.maxLength, u"maximum": _legacy_validators.maximum_draft3_draft4, u"minItems": _validators.minItems, u"minLength": _validators.minLength, u"minimum": _legacy_validators.minimum_draft3_draft4, u"pattern": _validators.pattern, u"patternProperties": _validators.patternProperties, u"properties": _legacy_validators.properties_draft3, u"type": _legacy_validators.type_draft3, u"uniqueItems": _validators.uniqueItems, }, type_checker=_types.draft3_type_checker, version="draft3", id_of=lambda schema: schema.get(u"id", ""), ) Draft4Validator = create( meta_schema=_utils.load_schema("draft4"), validators={ u"$ref": _validators.ref, u"additionalItems": _validators.additionalItems, u"additionalProperties": _validators.additionalProperties, u"allOf": _validators.allOf, u"anyOf": _validators.anyOf, u"dependencies": _validators.dependencies, u"enum": _validators.enum, u"format": _validators.format, u"items": _legacy_validators.items_draft3_draft4, u"maxItems": _validators.maxItems, u"maxLength": _validators.maxLength, u"maxProperties": _validators.maxProperties, u"maximum": _legacy_validators.maximum_draft3_draft4, u"minItems": _validators.minItems, u"minLength": _validators.minLength, u"minProperties": _validators.minProperties, u"minimum": _legacy_validators.minimum_draft3_draft4, u"multipleOf": _validators.multipleOf, u"not": _validators.not_, u"oneOf": _validators.oneOf, u"pattern": _validators.pattern, u"patternProperties": _validators.patternProperties, u"properties": _validators.properties, u"required": _validators.required, u"type": _validators.type, u"uniqueItems": _validators.uniqueItems, }, type_checker=_types.draft4_type_checker, version="draft4", id_of=lambda schema: schema.get(u"id", ""), ) Draft6Validator = create( meta_schema=_utils.load_schema("draft6"), validators={ u"$ref": _validators.ref, u"additionalItems": _validators.additionalItems, u"additionalProperties": _validators.additionalProperties, u"allOf": _validators.allOf, u"anyOf": _validators.anyOf, u"const": _validators.const, u"contains": _validators.contains, u"dependencies": _validators.dependencies, u"enum": _validators.enum, u"exclusiveMaximum": _validators.exclusiveMaximum, u"exclusiveMinimum": _validators.exclusiveMinimum, u"format": _validators.format, u"items": _validators.items, u"maxItems": _validators.maxItems, u"maxLength": _validators.maxLength, u"maxProperties": _validators.maxProperties, u"maximum": _validators.maximum, u"minItems": _validators.minItems, u"minLength": _validators.minLength, u"minProperties": _validators.minProperties, u"minimum": _validators.minimum, u"multipleOf": _validators.multipleOf, u"not": _validators.not_, u"oneOf": _validators.oneOf, u"pattern": _validators.pattern, u"patternProperties": _validators.patternProperties, u"properties": _validators.properties, u"propertyNames": _validators.propertyNames, u"required": _validators.required, u"type": _validators.type, u"uniqueItems": _validators.uniqueItems, }, type_checker=_types.draft6_type_checker, version="draft6", ) Draft7Validator = create( meta_schema=_utils.load_schema("draft7"), validators={ u"$ref": _validators.ref, u"additionalItems": _validators.additionalItems, u"additionalProperties": _validators.additionalProperties, u"allOf": _validators.allOf, u"anyOf": _validators.anyOf, u"const": _validators.const, u"contains": _validators.contains, u"dependencies": _validators.dependencies, u"enum": _validators.enum, u"exclusiveMaximum": _validators.exclusiveMaximum, u"exclusiveMinimum": _validators.exclusiveMinimum, u"format": _validators.format, u"if": _validators.if_, u"items": _validators.items, u"maxItems": _validators.maxItems, u"maxLength": _validators.maxLength, u"maxProperties": _validators.maxProperties, u"maximum": _validators.maximum, u"minItems": _validators.minItems, u"minLength": _validators.minLength, u"minProperties": _validators.minProperties, u"minimum": _validators.minimum, u"multipleOf": _validators.multipleOf, u"oneOf": _validators.oneOf, u"not": _validators.not_, u"pattern": _validators.pattern, u"patternProperties": _validators.patternProperties, u"properties": _validators.properties, u"propertyNames": _validators.propertyNames, u"required": _validators.required, u"type": _validators.type, u"uniqueItems": _validators.uniqueItems, }, type_checker=_types.draft7_type_checker, version="draft7", ) _LATEST_VERSION = Draft7Validator class RefResolver(object): """ Resolve JSON References. Arguments: base_uri (str): The URI of the referring document referrer: The actual referring document store (dict): A mapping from URIs to documents to cache cache_remote (bool): Whether remote refs should be cached after first resolution handlers (dict): A mapping from URI schemes to functions that should be used to retrieve them urljoin_cache (:func:`functools.lru_cache`): A cache that will be used for caching the results of joining the resolution scope to subscopes. remote_cache (:func:`functools.lru_cache`): A cache that will be used for caching the results of resolved remote URLs. Attributes: cache_remote (bool): Whether remote refs should be cached after first resolution """ def __init__( self, base_uri, referrer, store=(), cache_remote=True, handlers=(), urljoin_cache=None, remote_cache=None, ): if urljoin_cache is None: urljoin_cache = lru_cache(1024)(urljoin) if remote_cache is None: remote_cache = lru_cache(1024)(self.resolve_from_url) self.referrer = referrer self.cache_remote = cache_remote self.handlers = dict(handlers) self._scopes_stack = [base_uri] self.store = _utils.URIDict( (id, validator.META_SCHEMA) for id, validator in iteritems(meta_schemas) ) self.store.update(store) self.store[base_uri] = referrer self._urljoin_cache = urljoin_cache self._remote_cache = remote_cache @classmethod def from_schema(cls, schema, id_of=_id_of, *args, **kwargs): """ Construct a resolver from a JSON schema object. Arguments: schema: the referring schema Returns: `RefResolver` """ return cls(base_uri=id_of(schema), referrer=schema, *args, **kwargs) def push_scope(self, scope): """ Enter a given sub-scope. Treats further dereferences as being performed underneath the given scope. """ self._scopes_stack.append( self._urljoin_cache(self.resolution_scope, scope), ) def pop_scope(self): """ Exit the most recent entered scope. Treats further dereferences as being performed underneath the original scope. Don't call this method more times than `push_scope` has been called. """ try: self._scopes_stack.pop() except IndexError: raise exceptions.RefResolutionError( "Failed to pop the scope from an empty stack. " "`pop_scope()` should only be called once for every " "`push_scope()`" ) @property def resolution_scope(self): """ Retrieve the current resolution scope. """ return self._scopes_stack[-1] @property def base_uri(self): """ Retrieve the current base URI, not including any fragment. """ uri, _ = urldefrag(self.resolution_scope) return uri @contextlib.contextmanager def in_scope(self, scope): """ Temporarily enter the given scope for the duration of the context. """ self.push_scope(scope) try: yield finally: self.pop_scope() @contextlib.contextmanager def resolving(self, ref): """ Resolve the given ``ref`` and enter its resolution scope. Exits the scope on exit of this context manager. Arguments: ref (str): The reference to resolve """ url, resolved = self.resolve(ref) self.push_scope(url) try: yield resolved finally: self.pop_scope() def resolve(self, ref): """ Resolve the given reference. """ url = self._urljoin_cache(self.resolution_scope, ref) return url, self._remote_cache(url) def resolve_from_url(self, url): """ Resolve the given remote URL. """ url, fragment = urldefrag(url) try: document = self.store[url] except KeyError: try: document = self.resolve_remote(url) except Exception as exc: raise exceptions.RefResolutionError(exc) return self.resolve_fragment(document, fragment) def resolve_fragment(self, document, fragment): """ Resolve a ``fragment`` within the referenced ``document``. Arguments: document: The referent document fragment (str): a URI fragment to resolve within it """ fragment = fragment.lstrip(u"/") parts = unquote(fragment).split(u"/") if fragment else [] for part in parts: part = part.replace(u"~1", u"/").replace(u"~0", u"~") if isinstance(document, Sequence): # Array indexes should be turned into integers try: part = int(part) except ValueError: pass try: document = document[part] except (TypeError, LookupError): raise exceptions.RefResolutionError( "Unresolvable JSON pointer: %r" % fragment ) return document def resolve_remote(self, uri): """ Resolve a remote ``uri``. If called directly, does not check the store first, but after retrieving the document at the specified URI it will be saved in the store if :attr:`cache_remote` is True. .. note:: If the requests_ library is present, ``jsonschema`` will use it to request the remote ``uri``, so that the correct encoding is detected and used. If it isn't, or if the scheme of the ``uri`` is not ``http`` or ``https``, UTF-8 is assumed. Arguments: uri (str): The URI to resolve Returns: The retrieved document .. _requests: https://pypi.org/project/requests/ """ try: import requests except ImportError: requests = None scheme = urlsplit(uri).scheme if scheme in self.handlers: result = self.handlers[scheme](uri) elif scheme in [u"http", u"https"] and requests: # Requests has support for detecting the correct encoding of # json over http result = requests.get(uri).json() else: # Otherwise, pass off to urllib and assume utf-8 with urlopen(uri) as url: result = json.loads(url.read().decode("utf-8")) if self.cache_remote: self.store[uri] = result return result def validate(instance, schema, cls=None, *args, **kwargs): """ Validate an instance under the given schema. >>> validate([2, 3, 4], {"maxItems": 2}) Traceback (most recent call last): ... ValidationError: [2, 3, 4] is too long :func:`validate` will first verify that the provided schema is itself valid, since not doing so can lead to less obvious error messages and fail in less obvious or consistent ways. If you know you have a valid schema already, especially if you intend to validate multiple instances with the same schema, you likely would prefer using the `IValidator.validate` method directly on a specific validator (e.g. ``Draft7Validator.validate``). Arguments: instance: The instance to validate schema: The schema to validate with cls (IValidator): The class that will be used to validate the instance. If the ``cls`` argument is not provided, two things will happen in accordance with the specification. First, if the schema has a :validator:`$schema` property containing a known meta-schema [#]_ then the proper validator will be used. The specification recommends that all schemas contain :validator:`$schema` properties for this reason. If no :validator:`$schema` property is found, the default validator class is the latest released draft. Any other provided positional and keyword arguments will be passed on when instantiating the ``cls``. Raises: `jsonschema.exceptions.ValidationError` if the instance is invalid `jsonschema.exceptions.SchemaError` if the schema itself is invalid .. rubric:: Footnotes .. [#] known by a validator registered with `jsonschema.validators.validates` """ if cls is None: cls = validator_for(schema) cls.check_schema(schema) validator = cls(schema, *args, **kwargs) error = exceptions.best_match(validator.iter_errors(instance)) if error is not None: raise error def validator_for(schema, default=_LATEST_VERSION): """ Retrieve the validator class appropriate for validating the given schema. Uses the :validator:`$schema` property that should be present in the given schema to look up the appropriate validator class. Arguments: schema (collections.Mapping or bool): the schema to look at default: the default to return if the appropriate validator class cannot be determined. If unprovided, the default is to return the latest supported draft. """ if schema is True or schema is False or u"$schema" not in schema: return default if schema[u"$schema"] not in meta_schemas: warn( ( "The metaschema specified by $schema was not found. " "Using the latest draft to validate, but this will raise " "an error in the future." ), DeprecationWarning, stacklevel=2, ) return meta_schemas.get(schema[u"$schema"], _LATEST_VERSION)