Converted shopping list to use json util and added default override for json util (#12478)

* Converted shopping list to use json util, Added default override for json util

* Reverted accidental revert

* Fixed pylint issue

homeassistant/components/shopping_list.py

@@ -1,8 +1,6 @@
 """Component to manage a shopping list."""
 import asyncio
-import json
 import logging
-import os
 import uuid
 
 import voluptuous as vol
@@ -14,7 +12,7 @@ from homeassistant.components.http.data_validator import (
     RequestDataValidator)
 from homeassistant.helpers import intent
 import homeassistant.helpers.config_validation as cv
-
+from homeassistant.util.json import load_json, save_json
 
 DOMAIN = 'shopping_list'
 DEPENDENCIES = ['http']
@@ -101,18 +99,13 @@ class ShoppingData:
         """Load items."""
         def load():
             """Load the items synchronously."""
-            path = self.hass.config.path(PERSISTENCE)
-            if not os.path.isfile(path):
-                return []
-            with open(path) as file:
-                return json.loads(file.read())
+            return load_json(self.hass.config.path(PERSISTENCE), default=[])
 
         self.items = yield from self.hass.async_add_job(load)
 
     def save(self):
         """Save the items."""
-        with open(self.hass.config.path(PERSISTENCE), 'wt') as file:
-            file.write(json.dumps(self.items, sort_keys=True, indent=4))
+        save_json(self.hass.config.path(PERSISTENCE), self.items)
 
 
 class AddItemIntent(intent.IntentHandler):

homeassistant/util/json.py

@@ -8,8 +8,11 @@ from homeassistant.exceptions import HomeAssistantError
 
 _LOGGER = logging.getLogger(__name__)
 
+_UNDEFINED = object()
 
-def load_json(filename: str) -> Union[List, Dict]:
+
+def load_json(filename: str, default: Union[List, Dict] = _UNDEFINED) \
+        -> Union[List, Dict]:
     """Load JSON data from a file and return as dict or list.
 
     Defaults to returning empty dict if file is not found.
@@ -26,7 +29,7 @@ def load_json(filename: str) -> Union[List, Dict]:
     except OSError as error:
         _LOGGER.exception('JSON file reading failed: %s', filename)
         raise HomeAssistantError(error)
-    return {}  # (also evaluates to False)
+    return {} if default is _UNDEFINED else default
 
 
 def save_json(filename: str, config: Union[List, Dict]):