Source code for asdf.extension

# 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 abc

import six

from . import asdftypes
from . import resolver


@six.add_metaclass(abc.ABCMeta)
[docs]class AsdfExtension(object): """ Subclass to define an extension to ASDF. """ @classmethod def __subclasshook__(cls, C): if cls is AsdfExtension: return (hasattr(C, 'types') and hasattr(C, 'tag_mapping') and hasattr(C, 'url_mapping')) return NotImplemented @abc.abstractproperty def types(self): """ A list of AsdfType subclasses that describe how to store custom objects to and from ASDF. """ pass @abc.abstractproperty def tag_mapping(self): """ A list of 2-tuples or callables mapping YAML tag prefixes to JSON Schema URL prefixes. For each entry: - If a 2-tuple, the first part of the tuple is a YAML tag prefix to match. The second part is a string, where case the following are available as Python formatting tokens: - ``{tag}``: the complete YAML tag. - ``{tag_suffix}``: the part of the YAML tag after the matched prefix. - ``{tag_prefix}``: the matched YAML tag prefix. - If a callable, it is passed the entire YAML tag must return the entire JSON schema URL if it matches, otherwise, return `None`. Note that while JSON Schema URLs uniquely define a JSON Schema, they do not have to actually exist on an HTTP server and be fetchable (much like XML namespaces). For example, to match all YAML tags with the ``tag:nowhere.org:custom` prefix to the ``http://nowhere.org/schemas/custom/`` URL prefix:: return [('tag:nowhere.org:custom/', 'http://nowhere.org/schemas/custom/{tag_suffix}')] """ pass @abc.abstractproperty def url_mapping(self): """ A list of 2-tuples or callables mapping JSON Schema URLs to other URLs. This is useful if the JSON Schemas are not actually fetchable at their corresponding URLs but are on the local filesystem, or, to save bandwidth, we have a copy of fetchable schemas on the local filesystem. If neither is desirable, it may simply be the empty list. For each entry: - If a 2-tuple, the first part is a URL prefix to match. The second part is a string, where the following are available as Python formatting tokens: - ``{url}``: The entire JSON schema URL - ``{url_prefix}``: The matched URL prefix - ``{url_suffix}``: The part of the URL after the prefix. - If a callable, it is passed the entire JSON Schema URL and must return a resolvable URL pointing to the schema content. If it doesn't match, should return `None`. For example, to map a remote HTTP URL prefix to files installed alongside as data alongside Python module:: return [('http://nowhere.org/schemas/custom/1.0.0/', asdf.util.filepath_to_url( os.path.join(SCHEMA_PATH, 'stsci.edu')) + '/{url_suffix}.yaml' )] """ pass
class AsdfExtensionList(object): """ Manage a set of extensions that are in effect. """ def __init__(self, extensions): tag_mapping = [] url_mapping = [] validators = {} self._type_index = asdftypes.AsdfTypeIndex() for extension in extensions: if not isinstance(extension, AsdfExtension): raise TypeError( "Extension must implement asdftypes.AsdfExtension " "interface") tag_mapping.extend(extension.tag_mapping) url_mapping.extend(extension.url_mapping) for typ in extension.types: self._type_index.add_type(typ) validators.update(typ.validators) self._tag_mapping = resolver.Resolver(tag_mapping, 'tag') self._url_mapping = resolver.Resolver(url_mapping, 'url') self._validators = validators @property def tag_to_schema_resolver(self): return self._tag_mapping @property def url_mapping(self): return self._url_mapping @property def type_index(self): return self._type_index @property def validators(self): return self._validators class BuiltinExtension(object): """ This is the "extension" to ASDF that includes all the built-in tags. Even though it's not really an extension and it's always available, it's built in the same way as an extension. """ @property def types(self): return asdftypes._all_asdftypes @property def tag_mapping(self): return [ ('tag:stsci.edu:asdf', 'http://stsci.edu/schemas/asdf{tag_suffix}') ] @property def url_mapping(self): return resolver.DEFAULT_URL_MAPPING # A special singleton for the common case of when no extensions are used. _builtin_extension_list = AsdfExtensionList([BuiltinExtension()])