Source code for asdf.extension

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

import os
import abc
import warnings
from pkg_resources import iter_entry_points

import six
import importlib

from . import asdftypes
from . import resolver
from .version import version as asdf_version
from .util import get_class_name
from .exceptions import AsdfDeprecationWarning


__all__ = ['AsdfExtension', 'AsdfExtensionList']


ASDF_TEST_BUILD_ENV = 'ASDF_TEST_BUILD'


[docs]@six.add_metaclass(abc.ABCMeta) class AsdfExtension(object): """ Abstract base class defining 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 `asdf.CustomType` 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
[docs]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, extension) validators.update(typ.validators) for sibling in typ.versioned_siblings: self._type_index.add_type(sibling, extension) validators.update(sibling.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): """Deprecated. Use `tag_mapping` instead""" warnings.warn( "The 'tag_to_schema_resolver' property is deprecated. Use " "'tag_mapping' instead.", AsdfDeprecationWarning) return self._tag_mapping @property def tag_mapping(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 resolver.DEFAULT_TAG_TO_URL_MAPPING @property def url_mapping(self): return resolver.DEFAULT_URL_MAPPING class _DefaultExtensions: def __init__(self): self._extensions = [] self._extension_list = None self._package_metadata = {} def _load_installed_extensions(self, group='asdf_extensions'): for entry_point in iter_entry_points(group=group): ext = entry_point.load() if not issubclass(ext, AsdfExtension): warnings.warn("Found entry point {}, from {} but it is not a " "subclass of AsdfExtension, as expected. It is " "being ignored.".format(ext, entry_point.dist)) continue dist = entry_point.dist name = get_class_name(ext, instance=False) self._package_metadata[name] = (dist.project_name, dist.version) self._extensions.append(ext()) @property def extensions(self): # This helps avoid a circular dependency with external packages if not self._extensions: # If this environment variable is defined, load the default # extension. This allows the package to be tested without being # installed (e.g. for builds on Debian). if os.environ.get(ASDF_TEST_BUILD_ENV): # Fake the extension metadata name = get_class_name(BuiltinExtension, instance=False) self._package_metadata[name] = ('asdf', asdf_version) self._extensions.append(BuiltinExtension()) self._load_installed_extensions() return self._extensions @property def extension_list(self): if self._extension_list is None: self._extension_list = AsdfExtensionList(self.extensions) return self._extension_list @property def package_metadata(self): return self._package_metadata def reset(self): """This will be used primarily for testing purposes.""" self._extensions = [] self._extension_list = None self._package_metadata = {} default_extensions = _DefaultExtensions()