Add return type to json_loads (#85672)

* Add JSON type definitions

* Sample use

* Keep mutable for a follo-up PR (avoid dead code)

* Use list/dict

* Remove JsonObjectType

* Remove reference to Union

* Cleanup

* Improve rest

* Rename json_dict => json_data

* Add docstring

* Add type hint to json_loads

* Add cast

* Move type alias to json helpers

* Cleanup

* Create and use json_loads_object

* Make error more explicit and add tests

* Use JsonObjectType in conversation

* Remove quotes

tests/helpers/test_json.py

@@ -13,6 +13,7 @@ from homeassistant.helpers.json import (
     json_bytes_strip_null,
     json_dumps,
     json_dumps_sorted,
+    json_loads_object,
 )
 from homeassistant.util import dt as dt_util
 from homeassistant.util.color import RGBColor
@@ -135,3 +136,20 @@ def test_json_bytes_strip_null() -> None:
         json_bytes_strip_null([[{"k1": {"k2": ["silly\0stuff"]}}]])
         == b'[[{"k1":{"k2":["silly"]}}]]'
     )
+
+
+def test_json_loads_object():
+    """Test json_loads_object validates result."""
+    assert json_loads_object('{"c":1.2}') == {"c": 1.2}
+    with pytest.raises(
+        ValueError, match="Expected JSON to be parsed as a dict got <class 'list'>"
+    ):
+        json_loads_object("[]")
+    with pytest.raises(
+        ValueError, match="Expected JSON to be parsed as a dict got <class 'bool'>"
+    ):
+        json_loads_object("true")
+    with pytest.raises(
+        ValueError, match="Expected JSON to be parsed as a dict got <class 'NoneType'>"
+    ):
+        json_loads_object("null")