mirror of https://github.com/home-assistant/core
262 lines
8.5 KiB
Python
262 lines
8.5 KiB
Python
"""
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The methods for loading Home Assistant components.
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This module has quite some complex parts. I have tried to add as much
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documentation as possible to keep it understandable.
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Components can be accessed via hass.components.switch from your code.
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If you want to retrieve a platform that is part of a component, you should
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call get_component(hass, 'switch.your_platform'). In both cases the config
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directory is checked to see if it contains a user provided version. If not
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available it will check the built-in components and platforms.
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"""
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import functools as ft
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import importlib
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import logging
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import sys
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from types import ModuleType
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from typing import Optional, Set, TYPE_CHECKING, Callable, Any, TypeVar # noqa pylint: disable=unused-import
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from homeassistant.const import PLATFORM_FORMAT
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from homeassistant.util import OrderedSet
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# Typing imports that create a circular dependency
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# pylint: disable=using-constant-test,unused-import
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if TYPE_CHECKING:
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from homeassistant.core import HomeAssistant # NOQA
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CALLABLE_T = TypeVar('CALLABLE_T', bound=Callable) # noqa pylint: disable=invalid-name
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PREPARED = False
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DEPENDENCY_BLACKLIST = {'config'}
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_LOGGER = logging.getLogger(__name__)
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DATA_KEY = 'components'
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PATH_CUSTOM_COMPONENTS = 'custom_components'
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PACKAGE_COMPONENTS = 'homeassistant.components'
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def set_component(hass, # type: HomeAssistant
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comp_name: str, component: Optional[ModuleType]) -> None:
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"""Set a component in the cache.
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Async friendly.
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"""
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cache = hass.data.get(DATA_KEY)
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if cache is None:
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cache = hass.data[DATA_KEY] = {}
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cache[comp_name] = component
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def get_platform(hass, # type: HomeAssistant
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domain: str, platform: str) -> Optional[ModuleType]:
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"""Try to load specified platform.
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Async friendly.
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"""
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return get_component(hass, PLATFORM_FORMAT.format(domain, platform))
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def get_component(hass, # type: HomeAssistant
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comp_or_platform: str) -> Optional[ModuleType]:
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"""Try to load specified component.
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Looks in config dir first, then built-in components.
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Only returns it if also found to be valid.
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Async friendly.
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"""
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try:
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return hass.data[DATA_KEY][comp_or_platform] # type: ignore
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except KeyError:
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pass
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cache = hass.data.get(DATA_KEY)
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if cache is None:
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if hass.config.config_dir is None:
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_LOGGER.error("Can't load components - config dir is not set")
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return None
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# Only insert if it's not there (happens during tests)
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if sys.path[0] != hass.config.config_dir:
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sys.path.insert(0, hass.config.config_dir)
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cache = hass.data[DATA_KEY] = {}
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# First check custom, then built-in
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potential_paths = ['custom_components.{}'.format(comp_or_platform),
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'homeassistant.components.{}'.format(comp_or_platform)]
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for index, path in enumerate(potential_paths):
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try:
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module = importlib.import_module(path)
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# In Python 3 you can import files from directories that do not
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# contain the file __init__.py. A directory is a valid module if
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# it contains a file with the .py extension. In this case Python
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# will succeed in importing the directory as a module and call it
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# a namespace. We do not care about namespaces.
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# This prevents that when only
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# custom_components/switch/some_platform.py exists,
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# the import custom_components.switch would succeed.
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# __file__ was unset for namespaces before Python 3.7
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if getattr(module, '__file__', None) is None:
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continue
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_LOGGER.info("Loaded %s from %s", comp_or_platform, path)
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cache[comp_or_platform] = module
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if index == 0:
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_LOGGER.warning(
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'You are using a custom component for %s which has not '
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'been tested by Home Assistant. This component might '
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'cause stability problems, be sure to disable it if you '
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'do experience issues with Home Assistant.',
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comp_or_platform)
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return module
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except ImportError as err:
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# This error happens if for example custom_components/switch
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# exists and we try to load switch.demo.
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# Ignore errors for custom_components, custom_components.switch
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# and custom_components.switch.demo.
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white_listed_errors = []
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parts = []
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for part in path.split('.'):
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parts.append(part)
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white_listed_errors.append(
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"No module named '{}'".format('.'.join(parts)))
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if str(err) not in white_listed_errors:
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_LOGGER.exception(
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("Error loading %s. Make sure all "
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"dependencies are installed"), path)
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_LOGGER.error("Unable to find component %s", comp_or_platform)
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return None
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class ModuleWrapper:
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"""Class to wrap a Python module and auto fill in hass argument."""
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def __init__(self,
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hass, # type: HomeAssistant
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module: ModuleType) -> None:
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"""Initialize the module wrapper."""
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self._hass = hass
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self._module = module
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def __getattr__(self, attr: str) -> Any:
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"""Fetch an attribute."""
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value = getattr(self._module, attr)
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if hasattr(value, '__bind_hass'):
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value = ft.partial(value, self._hass)
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setattr(self, attr, value)
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return value
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class Components:
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"""Helper to load components."""
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def __init__(
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self,
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hass # type: HomeAssistant
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) -> None:
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"""Initialize the Components class."""
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self._hass = hass
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def __getattr__(self, comp_name: str) -> ModuleWrapper:
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"""Fetch a component."""
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component = get_component(self._hass, comp_name)
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if component is None:
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raise ImportError('Unable to load {}'.format(comp_name))
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wrapped = ModuleWrapper(self._hass, component)
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setattr(self, comp_name, wrapped)
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return wrapped
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class Helpers:
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"""Helper to load helpers."""
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def __init__(
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self,
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hass # type: HomeAssistant
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) -> None:
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"""Initialize the Helpers class."""
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self._hass = hass
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def __getattr__(self, helper_name: str) -> ModuleWrapper:
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"""Fetch a helper."""
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helper = importlib.import_module(
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'homeassistant.helpers.{}'.format(helper_name))
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wrapped = ModuleWrapper(self._hass, helper)
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setattr(self, helper_name, wrapped)
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return wrapped
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def bind_hass(func: CALLABLE_T) -> CALLABLE_T:
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"""Decorate function to indicate that first argument is hass."""
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setattr(func, '__bind_hass', True)
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return func
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def load_order_component(hass, # type: HomeAssistant
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comp_name: str) -> OrderedSet:
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"""Return an OrderedSet of components in the correct order of loading.
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Returns an empty list if a circular dependency is detected
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or the component could not be loaded. In both cases, the error is
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logged.
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Async friendly.
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"""
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return _load_order_component(hass, comp_name, OrderedSet(), set())
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def _load_order_component(hass, # type: HomeAssistant
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comp_name: str, load_order: OrderedSet,
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loading: Set) -> OrderedSet:
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"""Recursive function to get load order of components.
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Async friendly.
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"""
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component = get_component(hass, comp_name)
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# If None it does not exist, error already thrown by get_component.
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if component is None:
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return OrderedSet()
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loading.add(comp_name)
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for dependency in getattr(component, 'DEPENDENCIES', []):
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# Check not already loaded
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if dependency in load_order:
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continue
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# If we are already loading it, we have a circular dependency.
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if dependency in loading:
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_LOGGER.error("Circular dependency detected: %s -> %s",
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comp_name, dependency)
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return OrderedSet()
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dep_load_order = _load_order_component(
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hass, dependency, load_order, loading)
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# length == 0 means error loading dependency or children
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if not dep_load_order:
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_LOGGER.error("Error loading %s dependency: %s",
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comp_name, dependency)
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return OrderedSet()
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load_order.update(dep_load_order)
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load_order.add(comp_name)
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loading.remove(comp_name)
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return load_order
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