python-asdf 1.2.1-2 / usr / lib / python2.7 / dist-packages / asdf / schema.py

# Licensed under a 3-clause BSD style license - see LICENSE.rst
# -*- coding: utf-8 -*-

from __future__ import absolute_import, division, unicode_literals, print_function

import datetime
import json
import os

import six
from six.moves.urllib import parse as urlparse

from jsonschema import validators as mvalidators
from jsonschema.exceptions import ValidationError

import yaml

from .compat import lru_cache
from .compat.odict import OrderedDict
from . import constants
from . import generic_io
from . import reference
from . import resolver as mresolver
from . import treeutil
from . import util


YAML_SCHEMA_METASCHEMA_ID = 'http://stsci.edu/schemas/yaml-schema/draft-01'


if getattr(yaml, '__with_libyaml__', None):  # pragma: no cover
    _yaml_base_loader = yaml.CSafeLoader
else:  # pragma: no cover
    _yaml_base_loader = yaml.SafeLoader


__all__ = ['validate', 'fill_defaults', 'remove_defaults', 'check_schema']


SCHEMA_PATH = os.path.abspath(
    os.path.join(os.path.dirname(__file__), 'schemas'))


PYTHON_TYPE_TO_YAML_TAG = {
    None: 'null',
    six.text_type: 'str',
    bytes: 'str',
    bool: 'bool',
    int: 'int',
    float: 'float',
    list: 'seq',
    dict: 'map',
    set: 'set',
    OrderedDict: 'omap'
}


if six.PY2:
    PYTHON_TYPE_TO_YAML_TAG[long] = 'int'


# Prepend full YAML tag prefix
for k, v in PYTHON_TYPE_TO_YAML_TAG.items():
    PYTHON_TYPE_TO_YAML_TAG[k] = constants.YAML_TAG_PREFIX + v


def _type_to_tag(type_):
    for base in type_.mro():
        if base in PYTHON_TYPE_TO_YAML_TAG:
            return PYTHON_TYPE_TO_YAML_TAG[base]


def validate_tag(validator, tagname, instance, schema):
    # Shortcut: If the instance is a subclass of YAMLObject then we know it
    # should have a yaml_tag attribute attached; otherwise we have to use a
    # hack of reserializing the object and seeing what tags get attached to it
    # (though there may be a better way than this).

    if hasattr(instance, '_tag'):
        instance_tag = instance._tag
    else:
        # Try tags for known Python builtins
        instance_tag = _type_to_tag(type(instance))

    if instance_tag is not None and instance_tag != tagname:
        yield ValidationError(
            "mismatched tags, wanted '{0}', got '{1}'".format(
                tagname, instance_tag))


def validate_propertyOrder(validator, order, instance, schema):
    """
    Stores a value on the `tagged.TaggedDict` instance so that
    properties can be written out in the preferred order.  In that
    sense this isn't really a "validator", but using the `jsonschema`
    library's extensible validation system is the easiest way to get
    this property assigned.
    """
    if not validator.is_type(instance, 'object'):
        return

    if not order:
        # propertyOrder may be an empty list
        return

    instance.property_order = order


def validate_flowStyle(validator, flow_style, instance, schema):
    """
    Sets a flag on the `tagged.TaggedList` or `tagged.TaggedDict`
    object so that the YAML generator knows which style to use to
    write the element.  In that sense this isn't really a "validator",
    but using the `jsonschema` library's extensible validation system
    is the easiest way to get this property assigned.
    """
    if not (validator.is_type(instance, 'object') or
            validator.is_type(instance, 'array')):
        return

    instance.flow_style = flow_style


def validate_style(validator, style, instance, schema):
    """
    Sets a flag on the `tagged.TaggedString` object so that the YAML
    generator knows which style to use to write the string.  In that
    sense this isn't really a "validator", but using the `jsonschema`
    library's extensible validation system is the easiest way to get
    this property assigned.
    """
    if not validator.is_type(instance, 'string'):
        return

    instance.style = style


def validate_type(validator, types, instance, schema):
    """
    PyYAML returns strings that look like dates as datetime objects.
    However, as far as JSON is concerned, this is type==string and
    format==date-time.  That detects for that case and doesn't raise
    an error, otherwise falling back to the default type checker.
    """
    if (isinstance(instance, datetime.datetime) and
        schema.get('format') == 'date-time' and
        'string' in types):
        return

    return mvalidators.Draft4Validator.VALIDATORS['type'](
        validator, types, instance, schema)


YAML_VALIDATORS = util.HashableDict(
    mvalidators.Draft4Validator.VALIDATORS.copy())
YAML_VALIDATORS.update({
    'tag': validate_tag,
    'propertyOrder': validate_propertyOrder,
    'flowStyle': validate_flowStyle,
    'style': validate_style,
    'type': validate_type
})


def validate_fill_default(validator, properties, instance, schema):
    if not validator.is_type(instance, 'object'):
        return

    for property, subschema in six.iteritems(properties):
        if "default" in subschema:
            instance.setdefault(property, subschema["default"])

    for err in mvalidators.Draft4Validator.VALIDATORS['properties'](
        validator, properties, instance, schema):
        yield err


FILL_DEFAULTS = util.HashableDict()
for key in ('allOf', 'anyOf', 'oneOf', 'items'):
    FILL_DEFAULTS[key] = mvalidators.Draft4Validator.VALIDATORS[key]
FILL_DEFAULTS['properties'] = validate_fill_default


def validate_remove_default(validator, properties, instance, schema):
    if not validator.is_type(instance, 'object'):
        return

    for property, subschema in six.iteritems(properties):
        if subschema.get("default", None) is not None:
            if instance.get(property, None) == subschema["default"]:
                del instance[property]

    for err in mvalidators.Draft4Validator.VALIDATORS['properties'](
        validator, properties, instance, schema):
        yield err


REMOVE_DEFAULTS = util.HashableDict()
for key in ('allOf', 'anyOf', 'oneOf', 'items'):
    REMOVE_DEFAULTS[key] = mvalidators.Draft4Validator.VALIDATORS[key]
REMOVE_DEFAULTS['properties'] = validate_remove_default



@lru_cache()
def _create_validator(validators=YAML_VALIDATORS):
    meta_schema = load_schema(YAML_SCHEMA_METASCHEMA_ID,
                              mresolver.default_url_mapping)
    base_cls = mvalidators.create(meta_schema=meta_schema,
                                  validators=validators)

    class ASDFValidator(base_cls):
        DEFAULT_TYPES = base_cls.DEFAULT_TYPES.copy()
        DEFAULT_TYPES['array'] = (list, tuple)

        def iter_errors(self, instance, _schema=None, _seen=set()):
            # We can't validate anything that looks like an external reference,
            # since we don't have the actual content, so we just have to defer
            # it for now.  If the user cares about complete validation, they
            # can call `AsdfFile.resolve_references`.
            if id(instance) in _seen:
                return

            if _schema is None:
                schema = self.schema
            else:
                schema = _schema

            if ((isinstance(instance, dict) and '$ref' in instance) or
                    isinstance(instance, reference.Reference)):
                return

            if _schema is None:
                tag = getattr(instance, '_tag', None)
                if tag is not None:
                    schema_path = self.ctx.tag_to_schema_resolver(tag)
                    if schema_path != tag:
                        s = load_schema(schema_path, self.ctx.url_mapping)
                        if s:
                            with self.resolver.in_scope(schema_path):
                                for x in super(ASDFValidator, self).iter_errors(instance, s):
                                    yield x

                if isinstance(instance, dict):
                    new_seen = _seen | set([id(instance)])
                    for val in six.itervalues(instance):
                        for x in self.iter_errors(val, _seen=new_seen):
                            yield x

                elif isinstance(instance, list):
                    new_seen = _seen | set([id(instance)])
                    for val in instance:
                        for x in self.iter_errors(val, _seen=new_seen):
                            yield x
            else:
                for x in super(ASDFValidator, self).iter_errors(instance, _schema=schema):
                    yield x

    return ASDFValidator


# We want to load mappings in schema as ordered dicts
class OrderedLoader(_yaml_base_loader):
    pass


def construct_mapping(loader, node):
    loader.flatten_mapping(node)
    return OrderedDict(loader.construct_pairs(node))


OrderedLoader.add_constructor(
    yaml.resolver.BaseResolver.DEFAULT_MAPPING_TAG,
    construct_mapping)


if six.PY2:
    # Load strings in as Unicode on Python 2
    OrderedLoader.add_constructor('tag:yaml.org,2002:str',
                                  OrderedLoader.construct_scalar)


@lru_cache()
def _load_schema(url):
    with generic_io.get_file(url) as fd:
        if isinstance(url, six.text_type) and url.endswith('json'):
            result = json.load(fd, object_pairs_hook=OrderedDict)
        else:
            result = yaml.load(fd, Loader=OrderedLoader)
    return result, fd.uri


def _make_schema_loader(resolver):
    def load_schema(url):
        url = resolver(url)
        return _load_schema(url)
    return load_schema


def _make_resolver(url_mapping):
    handlers = {}
    schema_loader = _make_schema_loader(url_mapping)

    def get_schema(url):
        return schema_loader(url)[0]

    for x in ['http', 'https', 'file']:
        handlers[x] = get_schema

    # We set cache_remote=False here because we do the caching of
    # remote schemas here in `load_schema`, so we don't need
    # jsonschema to do it on our behalf.  Setting it to `True`
    # counterintuitively makes things slower.
    return mvalidators.RefResolver(
        '', {}, cache_remote=False, handlers=handlers)


def _load_draft4_metaschema():
    from jsonschema import _utils
    return _utils.load_schema('draft4')


# This is a list of schema that we have locally on disk but require
# special methods to obtain
HARDCODED_SCHEMA = {
    'http://json-schema.org/draft-04/schema': _load_draft4_metaschema
}


@lru_cache()
def load_schema(url, resolver=None, resolve_references=False):
    """
    Load a schema from the given URL.

    Parameters
    ----------
    url : str
        The path to the schema

    resolver : callable, optional
        A callback function used to map URIs to other URIs.  The
        callable must take a string and return a string or `None`.
        This is useful, for example, when a remote resource has a
        mirror on the local filesystem that you wish to use.

    resolve_references : bool, optional
        If `True`, resolve all `$ref` references.
    """
    if resolver is None:
        resolver = mresolver.default_url_mapping
    loader = _make_schema_loader(resolver)
    if url in HARDCODED_SCHEMA:
        schema = HARDCODED_SCHEMA[url]()
    else:
        schema, url = loader(url)

    if resolve_references:
        def resolve_refs(node, json_id):
            if json_id is None:
                json_id = url
            if isinstance(node, dict) and '$ref' in node:
                suburl = generic_io.resolve_uri(json_id, node['$ref'])
                parts = urlparse.urlparse(suburl)
                fragment = parts.fragment
                if len(fragment):
                    suburl_path = suburl[:-(len(fragment) + 1)]
                else:
                    suburl_path = suburl
                suburl_path = resolver(suburl_path)
                if suburl_path == url:
                    subschema = schema
                else:
                    subschema = load_schema(suburl_path, resolver, True)
                subschema_fragment = reference.resolve_fragment(
                    subschema, fragment)
                return subschema_fragment
            return node
        schema = treeutil.walk_and_modify(schema, resolve_refs)

    return schema


def get_validator(schema={}, ctx=None, validators=None, url_mapping=None,
                  *args, **kwargs):
    """
    Get a JSON schema validator object for the given schema.

    The additional *args and **kwargs are passed along to
    `jsonschema.validate`.

    Parameters
    ----------
    schema : schema, optional
        Explicit schema to use.  If not provided, the schema to use
        is determined by the tag on instance (or subinstance).

    ctx : AsdfFile context
        Used to resolve tags and urls

    validators : dict, optional
        A dictionary mapping properties to validators to use (instead
        of the built-in ones and ones provided by extension types).

    url_mapping : resolver.Resolver, optional
        A resolver to convert remote URLs into local ones.

    Returns
    -------
    validator : jsonschema.Validator
    """
    if ctx is None:
        from .asdf import AsdfFile
        ctx = AsdfFile()

    if validators is None:
        validators = util.HashableDict(YAML_VALIDATORS.copy())
        validators.update(ctx._extensions.validators)

    kwargs['resolver'] = _make_resolver(url_mapping)

    # We don't just call validators.validate() directly here, because
    # that validates the schema itself, wasting a lot of time (at the
    # time of this writing, it was half of the runtime of the unit
    # test suite!!!).  Instead, we assume that the schemas are valid
    # through the running of the unit tests, not at run time.
    cls = _create_validator(validators=validators)
    validator = cls(schema, *args, **kwargs)
    validator.ctx = ctx
    return validator


if six.PY2:
    def validate_large_literals(instance):
        """
        Validate that the tree has no large numeric literals.
        """
        # We can count on 52 bits of precision
        upper = ((long(1) << 51) - 1)
        lower = -((long(1) << 51) - 2)

        for instance in treeutil.iter_tree(instance):
            if (isinstance(instance, six.integer_types) and
                (instance > upper or instance < lower)):
                raise ValidationError(
                    "Integer value {0} is too large to safely represent as a "
                    "literal in ASDF".format(instance))
else:
    def validate_large_literals(instance):
        """
        Validate that the tree has no large numeric literals.
        """
        # We can count on 52 bits of precision
        for instance in treeutil.iter_tree(instance):
            if (isinstance(instance, int) and (
                instance > ((1 << 51) - 1) or
                instance < -((1 << 51) - 2))):
                raise ValidationError(
                    "Integer value {0} is too large to safely represent as a "
                    "literal in ASDF".format(instance))


def validate(instance, ctx=None, schema={},
             validators=None,
             *args, **kwargs):
    """
    Validate the given instance (which must be a tagged tree) against
    the appropriate schema.  The schema itself is located using the
    tag on the instance.

    The additional *args and **kwargs are passed along to
    `jsonschema.validate`.

    Parameters
    ----------
    instance : tagged tree

    ctx : AsdfFile context
        Used to resolve tags and urls

    schema : schema, optional
        Explicit schema to use.  If not provided, the schema to use
        is determined by the tag on instance (or subinstance).

    validators : dict, optional
        A dictionary mapping properties to validators to use (instead
        of the built-in ones and ones provided by extension types).
    """
    if ctx is None:
        from .asdf import AsdfFile
        ctx = AsdfFile()

    validator = get_validator(schema, ctx, validators, ctx.url_mapping,
                              *args, **kwargs)
    validator.validate(instance, _schema=(schema or None))

    validate_large_literals(instance)


def fill_defaults(instance, ctx):
    """
    For any default values in the schema, add them to the tree if they
    don't exist.

    Parameters
    ----------
    instance : tagged tree

    ctx : AsdfFile context
        Used to resolve tags and urls
    """
    validate(instance, ctx, validators=FILL_DEFAULTS)


def remove_defaults(instance, ctx):
    """
    For any values in the tree that are the same as the default values
    specified in the schema, remove them from the tree.

    Parameters
    ----------
    instance : tagged tree

    ctx : AsdfFile context
        Used to resolve tags and urls
    """
    validate(instance, ctx, validators=REMOVE_DEFAULTS)


def check_schema(schema):
    """
    Check a given schema to make sure it is valid YAML schema.
    """
    # We also want to validate the "default" values in the schema
    # against the schema itself.  jsonschema as a library doesn't do
    # this on its own.

    def validate_default(validator, default, instance, schema):
        if not validator.is_type(instance, 'object'):
            return

        if 'default' in instance:
            with instance_validator.resolver.in_scope(scope):
                for err in instance_validator.iter_errors(
                        instance['default'], instance):
                    yield err

    VALIDATORS = util.HashableDict(
        mvalidators.Draft4Validator.VALIDATORS.copy())
    VALIDATORS.update({
        'default': validate_default
    })

    meta_schema = load_schema(YAML_SCHEMA_METASCHEMA_ID,
                              mresolver.default_url_mapping)

    resolver = _make_resolver(mresolver.default_url_mapping)

    cls = mvalidators.create(meta_schema=meta_schema,
                             validators=VALIDATORS)
    validator = cls(meta_schema, resolver=resolver)

    instance_validator = mvalidators.Draft4Validator(schema, resolver=resolver)
    scope = schema.get('id', '')

    validator.validate(schema, _schema=meta_schema)