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