From 7cb0c98c03919af95865930b77506998e2a99c4b Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Thu, 17 Sep 2020 14:45:30 -0500
Subject: [PATCH] Log template listeners when debug logging is on (#40180)

---
 homeassistant/helpers/event.py | 14 ++++++++++++++
 tests/helpers/test_event.py    |  2 +-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/homeassistant/helpers/event.py b/homeassistant/helpers/event.py
index 435a265d9e0..3033b51b605 100644
--- a/homeassistant/helpers/event.py
+++ b/homeassistant/helpers/event.py
@@ -525,6 +525,11 @@ class _TrackTemplateResultInfo:
 
         self._last_info = self._info.copy()
         self._create_listeners()
+        _LOGGER.debug(
+            "Template group %s listens for %s",
+            self._track_templates,
+            self.listeners,
+        )
 
     @property
     def listeners(self) -> Dict:
@@ -683,6 +688,10 @@ class _TrackTemplateResultInfo:
             ):
                 continue
 
+            _LOGGER.debug(
+                "Template update %s triggered by event: %s", template.template, event
+            )
+
             self._info[template] = template.async_render_to_info(
                 track_template_.variables
             )
@@ -708,6 +717,11 @@ class _TrackTemplateResultInfo:
 
         if info_changed:
             self._update_listeners()
+            _LOGGER.debug(
+                "Template group %s listens for %s",
+                self._track_templates,
+                self.listeners,
+            )
             self._last_info = self._info.copy()
 
         if not updates:
diff --git a/tests/helpers/test_event.py b/tests/helpers/test_event.py
index ba14c8a757f..ced25f1ad5b 100644
--- a/tests/helpers/test_event.py
+++ b/tests/helpers/test_event.py
@@ -541,7 +541,7 @@ async def test_track_template_error(hass, caplog):
         hass.states.async_set("switch.not_exist", "off")
         await hass.async_block_till_done()
 
-    assert "lunch" not in caplog.text
+    assert "no filter named 'lunch'" not in caplog.text
     assert "TemplateAssertionError" not in caplog.text