mopidy.ext — Mopidy 3.0.1 documentation

# Source code for mopidy.ext

    import collections
    import logging
    from collections.abc import Mapping

    import pkg_resources

    from mopidy import config as config_lib
    from mopidy import exceptions
    from mopidy.internal import path

    logger = logging.getLogger(__name__)

    _extension_data_fields = [
        "extension",
        "entry_point",
        "config_schema",
        "config_defaults",
        "command",
    ]

    ExtensionData = collections.namedtuple("ExtensionData", _extension_data_fields)

    class Extension:

        """Base class for Mopidy extensions"""

        dist_name = None
        """The extension's distribution name, as registered on PyPI

        Example: ``Mopidy-Soundspot``
        """

        ext_name = None
        """The extension's short name, as used in setup.py and as config section
        name

        Example: ``soundspot``
        """

        version = None
        """The extension's version

        Should match the :attr:`__version__` attribute on the extension's main
        Python module and the version registered on PyPI.
        """

        def get_default_config(self):
            """The extension's default config as a bytestring

            :returns: bytes or unicode
            """
            raise NotImplementedError(
                'Add at least a config section with "enabled = true"'
            )

        def get_config_schema(self):
            """The extension's config validation schema

            :returns: :class:`~mopidy.config.schemas.ConfigSchema`
            """
            schema = config_lib.ConfigSchema(self.ext_name)
            schema["enabled"] = config_lib.Boolean()
            return schema

        @classmethod
        def get_cache_dir(cls, config):
            """Get or create cache directory for the extension.

            Use this directory to cache data that can safely be thrown away.

            :param config: the Mopidy config object
            :return: pathlib.Path
            """
            assert cls.ext_name is not None
            cache_dir_path = (
                path.expand_path(config["core"]["cache_dir"]) / cls.ext_name
            )
            path.get_or_create_dir(cache_dir_path)
            return cache_dir_path

        @classmethod
        def get_config_dir(cls, config):
            """Get or create configuration directory for the extension.

            :param config: the Mopidy config object
            :return: pathlib.Path
            """
            assert cls.ext_name is not None
            config_dir_path = (
                path.expand_path(config["core"]["config_dir"]) / cls.ext_name
            )
            path.get_or_create_dir(config_dir_path)
            return config_dir_path

        @classmethod
        def get_data_dir(cls, config):
            """Get or create data directory for the extension.

            Use this directory to store data that should be persistent.

            :param config: the Mopidy config object
            :returns: pathlib.Path
            """
            assert cls.ext_name is not None
            data_dir_path = (
                path.expand_path(config["core"]["data_dir"]) / cls.ext_name
            )
            path.get_or_create_dir(data_dir_path)
            return data_dir_path

        def get_command(self):
            """Command to expose to command line users running ``mopidy``.

            :returns:
              Instance of a :class:`~mopidy.commands.Command` class.
            """
            pass

        def validate_environment(self):
            """Checks if the extension can run in the current environment.

            Dependencies described by :file:`setup.py` are checked by Mopidy, so
            you should not check their presence here.

            If a problem is found, raise :exc:`~mopidy.exceptions.ExtensionError`
            with a message explaining the issue.

            :raises: :exc:`~mopidy.exceptions.ExtensionError`
            :returns: :class:`None`
            """
            pass

        def setup(self, registry):
            """
            Register the extension's components in the extension :class:`Registry`.

            For example, to register a backend::

                def setup(self, registry):
                    from .backend import SoundspotBackend
                    registry.add('backend', SoundspotBackend)

            See :class:`Registry` for a list of registry keys with a special
            meaning. Mopidy will instantiate and start any classes registered under
            the ``frontend`` and ``backend`` registry keys.

            This method can also be used for other setup tasks not involving the
            extension registry.

            :param registry: the extension registry
            :type registry: :class:`Registry`
            """
            raise NotImplementedError

    class Registry(Mapping):

        """Registry of components provided by Mopidy extensions.

        Passed to the :meth:`~Extension.setup` method of all extensions. The
        registry can be used like a dict of string keys and lists.

        Some keys have a special meaning, including, but not limited to:

        - ``backend`` is used for Mopidy backend classes.
        - ``frontend`` is used for Mopidy frontend classes.

        Extensions can use the registry for allow other to extend the extension
        itself. For example the ``Mopidy-Local`` historically used the
        ``local:library`` key to allow other extensions to register library
        providers for ``Mopidy-Local`` to use. Extensions should namespace
        custom keys with the extension's :attr:`~Extension.ext_name`,
        e.g. ``local:foo`` or ``http:bar``.
        """

        def __init__(self):
            self._registry = {}

        def add(self, name, cls):
            """Add a component to the registry.

            Multiple classes can be registered to the same name.
            """
            self._registry.setdefault(name, []).append(cls)

        def __getitem__(self, name):
            return self._registry.setdefault(name, [])

        def __iter__(self):
            return iter(self._registry)

        def __len__(self):
            return len(self._registry)

    def load_extensions():
        """Find all installed extensions.

        :returns: list of installed extensions
        """

        installed_extensions = []

        for entry_point in pkg_resources.iter_entry_points("mopidy.ext"):
            logger.debug("Loading entry point: %s", entry_point)
            try:
                extension_class = entry_point.resolve()
            except Exception as e:
                logger.exception(
                    f"Failed to load extension {entry_point.name}: {e}"
                )
                continue

            try:
                if not issubclass(extension_class, Extension):
                    raise TypeError  # issubclass raises TypeError on non-class
            except TypeError:
                logger.error(
                    "Entry point %s did not contain a valid extension" "class: %r",
                    entry_point.name,
                    extension_class,
                )
                continue

            try:
                extension = extension_class()
                config_schema = extension.get_config_schema()
                default_config = extension.get_default_config()
                command = extension.get_command()
            except Exception:
                logger.exception(
                    "Setup of extension from entry point %s failed, "
                    "ignoring extension.",
                    entry_point.name,
                )
                continue

            installed_extensions.append(
                ExtensionData(
                    extension, entry_point, config_schema, default_config, command
                )
            )

            logger.debug(
                "Loaded extension: %s %s", extension.dist_name, extension.version
            )

        names = (ed.extension.ext_name for ed in installed_extensions)
        logger.debug("Discovered extensions: %s", ", ".join(names))
        return installed_extensions

    def validate_extension_data(data):
        """Verify extension's dependencies and environment.

        :param extensions: an extension to check
        :returns: if extension should be run
        """

        logger.debug("Validating extension: %s", data.extension.ext_name)

        if data.extension.ext_name != data.entry_point.name:
            logger.warning(
                "Disabled extension %(ep)s: entry point name (%(ep)s) "
                "does not match extension name (%(ext)s)",
                {"ep": data.entry_point.name, "ext": data.extension.ext_name},
            )
            return False

        try:
            data.entry_point.require()
        except pkg_resources.DistributionNotFound as exc:
            logger.info(
                "Disabled extension %s: Dependency %s not found",
                data.extension.ext_name,
                exc,
            )
            return False
        except pkg_resources.VersionConflict as exc:
            if len(exc.args) == 2:
                found, required = exc.args
                logger.info(
                    "Disabled extension %s: %s required, but found %s at %s",
                    data.extension.ext_name,
                    required,
                    found,
                    found.location,
                )
            else:
                logger.info(
                    "Disabled extension %s: %s", data.extension.ext_name, exc
                )
            return False

        try:
            data.extension.validate_environment()
        except exceptions.ExtensionError as exc:
            logger.info("Disabled extension %s: %s", data.extension.ext_name, exc)
            return False
        except Exception:
            logger.exception(
                "Validating extension %s failed with an exception.",
                data.extension.ext_name,
            )
            return False

        if not data.config_schema:
            logger.error(
                "Extension %s does not have a config schema, disabling.",
                data.extension.ext_name,
            )
            return False
        elif not isinstance(data.config_schema.get("enabled"), config_lib.Boolean):
            logger.error(
                'Extension %s does not have the required "enabled" config'
                " option, disabling.",
                data.extension.ext_name,
            )
            return False

        for key, value in data.config_schema.items():
            if not isinstance(value, config_lib.ConfigValue):
                logger.error(
                    "Extension %s config schema contains an invalid value"
                    ' for the option "%s", disabling.',
                    data.extension.ext_name,
                    key,
                )
                return False

        if not data.config_defaults:
            logger.error(
                "Extension %s does not have a default config, disabling.",
                data.extension.ext_name,
            )
            return False

        return True