Improve flexibility of the loader

This commit is contained in:
Paulus Schoutsen 2014-11-14 23:17:18 -08:00
parent 0c7b6e26aa
commit 973ce21353

View file

@ -3,7 +3,17 @@ homeassistant.loader
~~~~~~~~~~~~~~~~~~~~
Provides methods for loading Home Assistant components.
This module has quite some complex parts. I have tried to add as much
documentation as possible to keep it understandable.
Components are loaded by calling get_component('switch') from your code.
If you want to retrieve a platform that is part of a component, you should
call get_component('switch.your_platform'). In both cases the config directory
is checked to see if it contains a user provided version. If not available it
will check the built-in components and platforms.
"""
import os
import sys
import pkgutil
import importlib
@ -30,22 +40,27 @@ def prepare(hass):
pkgutil.iter_modules(components.__path__, 'homeassistant.components.'))
# Look for available custom components
custom_path = hass.get_config_path("custom_components")
# Ensure we can load custom components from the config dir
sys.path.append(hass.config_dir)
if os.path.isdir(custom_path):
# Ensure we can load custom components using Pythons import
sys.path.insert(0, hass.config_dir)
try:
# pylint: disable=import-error
import custom_components
# We cannot use the same approach as for built-in components because
# custom components might only contain a platform for a component.
# ie custom_components/switch/some_platform.py. Using pkgutil would
# not give us the switch component (and neither should it).
AVAILABLE_COMPONENTS.extend(
item[1] for item in
pkgutil.iter_modules(
custom_components.__path__, 'custom_components.'))
# Assumption: the custom_components dir only contains directories or
# python components. If this assumption is not true, HA won't break,
# just might output more errors.
for fil in os.listdir(custom_path):
if os.path.isdir(os.path.join(custom_path, fil)):
AVAILABLE_COMPONENTS.append('custom_components.{}'.format(fil))
except ImportError:
# No folder custom_components exist in the config directory
pass
else:
AVAILABLE_COMPONENTS.append(
'custom_components.{}'.format(fil[0:-3]))
def get_component(comp_name):
@ -61,8 +76,10 @@ def get_component(comp_name):
# an exception because it will try to import the parent.
# Because of this behavior, we will approach loading sub components
# with caution: only load it if we can verify that the parent exists.
# We do not want to silent the ImportErrors as they provide valuable
# information to track down when debugging Home Assistant.
# First check config dir, then built-in
# First check custom, then built-in
potential_paths = ['custom_components.{}'.format(comp_name),
'homeassistant.components.{}'.format(comp_name)]
@ -76,17 +93,30 @@ def get_component(comp_name):
continue
try:
_COMPONENT_CACHE[comp_name] = importlib.import_module(path)
module = importlib.import_module(path)
# In Python 3 you can import files from directories that do not
# contain the file __init__.py. A directory is a valid module if
# it contains a file with the .py extension. In this case Python
# will succeed in importing the directory as a module and call it
# a namespace. We do not care about namespaces.
# This prevents that when only
# custom_components/switch/some_platform.py exists,
# the import custom_components.switch would succeeed.
if module.__spec__.origin == 'namespace':
continue
_LOGGER.info("Loaded %s from %s", comp_name, path)
return _COMPONENT_CACHE[comp_name]
_COMPONENT_CACHE[comp_name] = module
return module
except ImportError:
_LOGGER.exception(
("Error loading %s. Make sure all "
"dependencies are installed"), path)
# We did find components but were unable to load them
_LOGGER.error("Unable to load component %s", comp_name)
_LOGGER.error("Unable to find component %s", comp_name)
return None