Add datetime_today template method (#57435)

tests/helpers/test_template.py

@@ -1080,6 +1080,44 @@ def test_utcnow(mock_is_safe, hass):
     assert info.has_time is True
 
 
+@patch(
+    "homeassistant.helpers.template.TemplateEnvironment.is_safe_callable",
+    return_value=True,
+)
+def test_today_at(mock_is_safe, hass):
+    """Test today_at method."""
+    now = dt_util.now()
+    with patch("homeassistant.util.dt.now", return_value=now):
+        now = now.replace(hour=10, minute=0, second=0, microsecond=0)
+        result = template.Template(
+            "{{ today_at('10:00').isoformat() }}",
+            hass,
+        ).async_render()
+        assert result == now.isoformat()
+
+        result = template.Template(
+            "{{ today_at('10:00:00').isoformat() }}",
+            hass,
+        ).async_render()
+        assert result == now.isoformat()
+
+        result = template.Template(
+            "{{ ('10:00:00' | today_at).isoformat() }}",
+            hass,
+        ).async_render()
+        assert result == now.isoformat()
+
+        now = now.replace(hour=0)
+        result = template.Template(
+            "{{ today_at().isoformat() }}",
+            hass,
+        ).async_render()
+        assert result == now.isoformat()
+
+        with pytest.raises(TemplateError):
+            template.Template("{{ today_at('bad') }}", hass).async_render()
+
+
 @patch(
     "homeassistant.helpers.template.TemplateEnvironment.is_safe_callable",
     return_value=True,