Add datetime_today template method (#57435)

homeassistant/helpers/template.py

@@ -1576,6 +1576,20 @@ def random_every_time(context, values):
     return random.choice(values)
 
 
+def today_at(time_str: str = "") -> datetime:
+    """Record fetching now where the time has been replaced with value."""
+    start = dt_util.start_of_local_day(datetime.now())
+
+    dttime = start.time() if time_str == "" else dt_util.parse_time(time_str)
+
+    if dttime:
+        return datetime.combine(start.date(), dttime, tzinfo=dt_util.DEFAULT_TIME_ZONE)
+
+    raise ValueError(
+        f"could not convert {type(time_str).__name__} to datetime: '{time_str}'"
+    )
+
+
 def relative_time(value):
     """
     Take a datetime and return its "age" as a string.
@@ -1685,6 +1699,7 @@ class TemplateEnvironment(ImmutableSandboxedEnvironment):
         self.filters["sqrt"] = square_root
         self.filters["as_datetime"] = dt_util.parse_datetime
         self.filters["as_timestamp"] = forgiving_as_timestamp
+        self.filters["today_at"] = today_at
         self.filters["as_local"] = dt_util.as_local
         self.filters["timestamp_custom"] = timestamp_custom
         self.filters["timestamp_local"] = timestamp_local
@@ -1725,6 +1740,7 @@ class TemplateEnvironment(ImmutableSandboxedEnvironment):
         self.globals["as_datetime"] = dt_util.parse_datetime
         self.globals["as_local"] = dt_util.as_local
         self.globals["as_timestamp"] = forgiving_as_timestamp
+        self.globals["today_at"] = today_at
         self.globals["relative_time"] = relative_time
         self.globals["timedelta"] = timedelta
         self.globals["strptime"] = strptime

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,