Return history for entities in the order they were requested (#25560)

* Return history for entities in the order they were requested

* Fix problems. Add tests

* Update __init__.py

homeassistant/components/history/__init__.py

@@ -211,6 +211,9 @@ def states_to_json(
     axis correctly.
     """
     result = defaultdict(list)
+    if entity_ids is not None:
+        for ent_id in entity_ids:
+            result[ent_id] = []
 
     # Get the states at the start time
     timer_start = time.perf_counter()

tests/components/history/test_init.py

@@ -428,6 +428,22 @@ class TestComponentHistory(unittest.TestCase):
                     history.CONF_ENTITIES: ['media_player.test']}}})
         self.check_significant_states(zero, four, states, config)
 
+    def test_get_significant_states_are_ordered(self):
+        """Test order of results from get_significant_states
+
+        When entity ids are given, the results should be returned with the data
+        in the same order.
+        """
+        zero, four, states = self.record_states()
+        entity_ids = ['media_player.test', 'media_player.test2']
+        hist = history.get_significant_states(
+            self.hass, zero, four, entity_ids, filters=history.Filters())
+        assert list(hist.keys()) == entity_ids
+        entity_ids = ['media_player.test2', 'media_player.test']
+        hist = history.get_significant_states(
+            self.hass, zero, four, entity_ids, filters=history.Filters())
+        assert list(hist.keys()) == entity_ids
+
     def check_significant_states(self, zero, four, states, config):
         """Check if significant states are retrieved."""
         filters = history.Filters()