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395 lines
11 KiB
395 lines
11 KiB
"""
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Validation errors, and some surrounding helpers.
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"""
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from __future__ import annotations
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from collections import defaultdict, deque
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from pprint import pformat
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from textwrap import dedent, indent
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import heapq
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import itertools
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import attr
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from jsonschema import _utils
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WEAK_MATCHES: frozenset[str] = frozenset(["anyOf", "oneOf"])
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STRONG_MATCHES: frozenset[str] = frozenset()
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_unset = _utils.Unset()
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class _Error(Exception):
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def __init__(
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self,
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message,
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validator=_unset,
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path=(),
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cause=None,
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context=(),
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validator_value=_unset,
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instance=_unset,
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schema=_unset,
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schema_path=(),
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parent=None,
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type_checker=_unset,
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):
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super(_Error, self).__init__(
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message,
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validator,
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path,
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cause,
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context,
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validator_value,
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instance,
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schema,
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schema_path,
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parent,
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)
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self.message = message
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self.path = self.relative_path = deque(path)
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self.schema_path = self.relative_schema_path = deque(schema_path)
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self.context = list(context)
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self.cause = self.__cause__ = cause
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self.validator = validator
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self.validator_value = validator_value
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self.instance = instance
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self.schema = schema
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self.parent = parent
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self._type_checker = type_checker
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for error in context:
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error.parent = self
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def __repr__(self):
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return f"<{self.__class__.__name__}: {self.message!r}>"
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def __str__(self):
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essential_for_verbose = (
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self.validator, self.validator_value, self.instance, self.schema,
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)
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if any(m is _unset for m in essential_for_verbose):
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return self.message
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schema_path = _utils.format_as_index(
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container=self._word_for_schema_in_error_message,
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indices=list(self.relative_schema_path)[:-1],
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)
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instance_path = _utils.format_as_index(
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container=self._word_for_instance_in_error_message,
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indices=self.relative_path,
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)
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prefix = 16 * " "
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return dedent(
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f"""\
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{self.message}
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Failed validating {self.validator!r} in {schema_path}:
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{indent(pformat(self.schema, width=72), prefix).lstrip()}
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On {instance_path}:
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{indent(pformat(self.instance, width=72), prefix).lstrip()}
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""".rstrip(),
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)
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@classmethod
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def create_from(cls, other):
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return cls(**other._contents())
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@property
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def absolute_path(self):
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parent = self.parent
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if parent is None:
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return self.relative_path
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path = deque(self.relative_path)
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path.extendleft(reversed(parent.absolute_path))
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return path
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@property
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def absolute_schema_path(self):
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parent = self.parent
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if parent is None:
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return self.relative_schema_path
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path = deque(self.relative_schema_path)
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path.extendleft(reversed(parent.absolute_schema_path))
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return path
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@property
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def json_path(self):
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path = "$"
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for elem in self.absolute_path:
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if isinstance(elem, int):
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path += "[" + str(elem) + "]"
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else:
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path += "." + elem
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return path
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def _set(self, type_checker=None, **kwargs):
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if type_checker is not None and self._type_checker is _unset:
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self._type_checker = type_checker
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for k, v in kwargs.items():
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if getattr(self, k) is _unset:
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setattr(self, k, v)
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def _contents(self):
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attrs = (
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"message", "cause", "context", "validator", "validator_value",
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"path", "schema_path", "instance", "schema", "parent",
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)
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return dict((attr, getattr(self, attr)) for attr in attrs)
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def _matches_type(self):
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try:
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expected = self.schema["type"]
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except (KeyError, TypeError):
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return False
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if isinstance(expected, str):
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return self._type_checker.is_type(self.instance, expected)
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return any(
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self._type_checker.is_type(self.instance, expected_type)
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for expected_type in expected
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)
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class ValidationError(_Error):
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"""
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An instance was invalid under a provided schema.
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"""
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_word_for_schema_in_error_message = "schema"
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_word_for_instance_in_error_message = "instance"
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class SchemaError(_Error):
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"""
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A schema was invalid under its corresponding metaschema.
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"""
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_word_for_schema_in_error_message = "metaschema"
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_word_for_instance_in_error_message = "schema"
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@attr.s(hash=True)
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class RefResolutionError(Exception):
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"""
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A ref could not be resolved.
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"""
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_cause = attr.ib()
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def __str__(self):
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return str(self._cause)
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class UndefinedTypeCheck(Exception):
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"""
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A type checker was asked to check a type it did not have registered.
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"""
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def __init__(self, type):
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self.type = type
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def __str__(self):
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return f"Type {self.type!r} is unknown to this type checker"
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class UnknownType(Exception):
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"""
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A validator was asked to validate an instance against an unknown type.
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"""
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def __init__(self, type, instance, schema):
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self.type = type
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self.instance = instance
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self.schema = schema
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def __str__(self):
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prefix = 16 * " "
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return dedent(
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f"""\
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Unknown type {self.type!r} for validator with schema:
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{indent(pformat(self.schema, width=72), prefix).lstrip()}
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While checking instance:
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{indent(pformat(self.instance, width=72), prefix).lstrip()}
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""".rstrip(),
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)
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class FormatError(Exception):
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"""
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Validating a format failed.
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"""
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def __init__(self, message, cause=None):
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super(FormatError, self).__init__(message, cause)
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self.message = message
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self.cause = self.__cause__ = cause
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def __str__(self):
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return self.message
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class ErrorTree(object):
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"""
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ErrorTrees make it easier to check which validations failed.
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"""
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_instance = _unset
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def __init__(self, errors=()):
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self.errors = {}
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self._contents = defaultdict(self.__class__)
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for error in errors:
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container = self
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for element in error.path:
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container = container[element]
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container.errors[error.validator] = error
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container._instance = error.instance
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def __contains__(self, index):
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"""
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Check whether ``instance[index]`` has any errors.
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"""
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return index in self._contents
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def __getitem__(self, index):
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"""
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Retrieve the child tree one level down at the given ``index``.
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If the index is not in the instance that this tree corresponds
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to and is not known by this tree, whatever error would be raised
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by ``instance.__getitem__`` will be propagated (usually this is
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some subclass of `LookupError`.
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"""
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if self._instance is not _unset and index not in self:
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self._instance[index]
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return self._contents[index]
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def __setitem__(self, index, value):
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"""
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Add an error to the tree at the given ``index``.
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"""
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self._contents[index] = value
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def __iter__(self):
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"""
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Iterate (non-recursively) over the indices in the instance with errors.
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"""
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return iter(self._contents)
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def __len__(self):
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"""
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Return the `total_errors`.
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"""
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return self.total_errors
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def __repr__(self):
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return f"<{self.__class__.__name__} ({len(self)} total errors)>"
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@property
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def total_errors(self):
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"""
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The total number of errors in the entire tree, including children.
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"""
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child_errors = sum(len(tree) for _, tree in self._contents.items())
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return len(self.errors) + child_errors
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def by_relevance(weak=WEAK_MATCHES, strong=STRONG_MATCHES):
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"""
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Create a key function that can be used to sort errors by relevance.
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Arguments:
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weak (set):
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a collection of validation keywords to consider to be
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"weak". If there are two errors at the same level of the
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instance and one is in the set of weak validation keywords,
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the other error will take priority. By default, :kw:`anyOf`
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and :kw:`oneOf` are considered weak keywords and will be
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superseded by other same-level validation errors.
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strong (set):
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a collection of validation keywords to consider to be
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"strong"
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"""
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def relevance(error):
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validator = error.validator
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return (
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-len(error.path),
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validator not in weak,
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validator in strong,
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not error._matches_type(),
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)
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return relevance
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relevance = by_relevance()
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def best_match(errors, key=relevance):
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"""
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Try to find an error that appears to be the best match among given errors.
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In general, errors that are higher up in the instance (i.e. for which
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`ValidationError.path` is shorter) are considered better matches,
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since they indicate "more" is wrong with the instance.
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If the resulting match is either :kw:`oneOf` or :kw:`anyOf`, the
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*opposite* assumption is made -- i.e. the deepest error is picked,
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since these keywords only need to match once, and any other errors
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may not be relevant.
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Arguments:
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errors (collections.abc.Iterable):
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the errors to select from. Do not provide a mixture of
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errors from different validation attempts (i.e. from
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different instances or schemas), since it won't produce
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sensical output.
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key (collections.abc.Callable):
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the key to use when sorting errors. See `relevance` and
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transitively `by_relevance` for more details (the default is
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to sort with the defaults of that function). Changing the
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default is only useful if you want to change the function
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that rates errors but still want the error context descent
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done by this function.
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Returns:
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the best matching error, or ``None`` if the iterable was empty
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.. note::
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This function is a heuristic. Its return value may change for a given
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set of inputs from version to version if better heuristics are added.
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"""
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errors = iter(errors)
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best = next(errors, None)
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if best is None:
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return
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best = max(itertools.chain([best], errors), key=key)
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while best.context:
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# Calculate the minimum via nsmallest, because we don't recurse if
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# all nested errors have the same relevance (i.e. if min == max == all)
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smallest = heapq.nsmallest(2, best.context, key=key)
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if len(smallest) == 2 and key(smallest[0]) == key(smallest[1]):
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return best
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best = smallest[0]
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return best
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