Limit dependencies of HA core (#2762)

homeassistant/core.py

@@ -9,22 +9,17 @@ import enum
 import functools as ft
 import logging
 import os
+import re
 import signal
 import threading
 import time
 from types import MappingProxyType
 
 # pylint: disable=unused-import
-from typing import Optional, Any, Callable  # NOQA
+from typing import Optional, Any, Callable, List  # NOQA
 
 import voluptuous as vol
 
-from homeassistant.helpers.typing import UnitSystemType  # NOQA
-
-import homeassistant.util as util
-import homeassistant.util.dt as dt_util
-import homeassistant.util.location as location
-from homeassistant.config import get_default_config_dir
 from homeassistant.const import (
     ATTR_DOMAIN, ATTR_FRIENDLY_NAME, ATTR_NOW, ATTR_SERVICE,
     ATTR_SERVICE_CALL_ID, ATTR_SERVICE_DATA, EVENT_CALL_SERVICE,
@@ -34,10 +29,11 @@ from homeassistant.const import (
     SERVICE_HOMEASSISTANT_RESTART, SERVICE_HOMEASSISTANT_STOP, __version__)
 from homeassistant.exceptions import (
     HomeAssistantError, InvalidEntityFormatError)
-from homeassistant.helpers.entity import split_entity_id, valid_entity_id
-from homeassistant.helpers.unit_system import (
-    METRIC_SYSTEM,
-)
+from homeassistant.helpers.typing import UnitSystemType  # NOQA
+from homeassistant.helpers.unit_system import METRIC_SYSTEM
+import homeassistant.util as util
+import homeassistant.util.dt as dt_util
+import homeassistant.util.location as location
 
 DOMAIN = "homeassistant"
 
@@ -52,9 +48,22 @@ SERVICE_CALL_LIMIT = 10  # seconds
 # will be added for each component that polls devices.
 MIN_WORKER_THREAD = 2
 
+# Pattern for validating entity IDs (format: <domain>.<entity>)
+ENTITY_ID_PATTERN = re.compile(r"^(\w+)\.(\w+)$")
+
 _LOGGER = logging.getLogger(__name__)
 
 
+def split_entity_id(entity_id: str) -> List[str]:
+    """Split a state entity_id into domain, object_id."""
+    return entity_id.split(".", 1)
+
+
+def valid_entity_id(entity_id: str) -> bool:
+    """Test if an entity ID is a valid format."""
+    return ENTITY_ID_PATTERN.match(entity_id) is not None
+
+
 class CoreState(enum.Enum):
     """Represent the current state of Home Assistant."""
 
@@ -734,7 +743,7 @@ class Config(object):
         self.api = None
 
         # Directory that holds the configuration
-        self.config_dir = get_default_config_dir()
+        self.config_dir = None
 
     def distance(self: object, lat: float, lon: float) -> float:
         """Calculate distance from Home Assistant."""
@@ -743,6 +752,8 @@ class Config(object):
 
     def path(self, *path):
         """Generate path to the file within the config dir."""
+        if self.config_dir is None:
+            raise HomeAssistantError("config_dir is not set")
         return os.path.join(self.config_dir, *path)
 
     def as_dict(self):