Don't gather TRIGGER_PLATFORM_SUBSCRIPTIONS (#147954)

Co-authored-by: Abílio Costa <abmantis@users.noreply.github.com>

homeassistant/helpers/trigger.py

@@ -147,11 +147,15 @@ async def _register_trigger_platform(
         )
         return
 
-    tasks: list[asyncio.Task[None]] = [
-        create_eager_task(listener(new_triggers))
-        for listener in hass.data[TRIGGER_PLATFORM_SUBSCRIPTIONS]
-    ]
-    await asyncio.gather(*tasks)
+    # We don't use gather here because gather adds additional overhead
+    # when wrapping each coroutine in a task, and we expect our listeners
+    # to call trigger.async_get_all_descriptions which will only yield
+    # the first time it's called, after that it returns cached data.
+    for listener in hass.data[TRIGGER_PLATFORM_SUBSCRIPTIONS]:
+        try:
+            await listener(new_triggers)
+        except Exception:
+            _LOGGER.exception("Error while notifying trigger platform listener")
 
 
 class Trigger(abc.ABC):

tests/helpers/test_trigger.py

@@ -738,3 +738,45 @@ async def test_invalid_trigger_platform(
     await async_setup_component(hass, "test", {})
 
     assert "Integration test does not provide trigger support, skipping" in caplog.text
+
+
+@patch("annotatedyaml.loader.load_yaml")
+@patch.object(Integration, "has_triggers", return_value=True)
+async def test_subscribe_triggers(
+    mock_has_triggers: Mock,
+    mock_load_yaml: Mock,
+    hass: HomeAssistant,
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """Test trigger.async_subscribe_platform_events."""
+    sun_trigger_descriptions = """
+        sun: {}
+        """
+
+    def _load_yaml(fname, secrets=None):
+        if fname.endswith("sun/triggers.yaml"):
+            trigger_descriptions = sun_trigger_descriptions
+        else:
+            raise FileNotFoundError
+        with io.StringIO(trigger_descriptions) as file:
+            return parse_yaml(file)
+
+    mock_load_yaml.side_effect = _load_yaml
+
+    async def broken_subscriber(_):
+        """Simulate a broken subscriber."""
+        raise Exception("Boom!")  # noqa: TRY002
+
+    trigger_events = []
+
+    async def good_subscriber(new_triggers: set[str]):
+        """Simulate a working subscriber."""
+        trigger_events.append(new_triggers)
+
+    trigger.async_subscribe_platform_events(hass, broken_subscriber)
+    trigger.async_subscribe_platform_events(hass, good_subscriber)
+
+    assert await async_setup_component(hass, "sun", {})
+
+    assert trigger_events == [{"sun"}]
+    assert "Error while notifying trigger platform listener" in caplog.text