Log when events are (unexpectedly) filtered out of responses in tests (#14213)

See https://github.com/matrix-org/synapse/pull/14095#discussion_r990335492

This is useful because when see that a relevant event is an `outlier` or `soft-failed`, then that's a good unexpected indicator explaining why it's not showing up. `filter_events_for_client` is used in `/sync`, `/messages`, `/context` which are all common end-to-end assertion touch points (also notifications, relations).

1 files changed, 12 insertions, 0 deletions

diff --git a/tests/test_utils/logging_setup.py b/tests/test_utils/logging_setup.py

index c37f205ed0..199bb06a81 100644
--- a/tests/test_utils/logging_setup.py
+++ b/tests/test_utils/logging_setup.py
@@ -53,4 +53,16 @@ def setup_logging() -> None:
     log_level = os.environ.get("SYNAPSE_TEST_LOG_LEVEL", "ERROR")
     root_logger.setLevel(log_level)
 
+    # In order to not add noise by default (since we only log ERROR messages for trial
+    # tests as configured above), we only enable this for developers for looking for
+    # more INFO or DEBUG.
+    if root_logger.isEnabledFor(logging.INFO):
+        # Log when events are (maybe unexpectedly) filtered out of responses in tests. It's
+        # just nice to be able to look at the CI log and figure out why an event isn't being
+        # returned.
+        logging.getLogger("synapse.visibility.filtered_event_debug").setLevel(
+            logging.DEBUG
+        )
+
+    # Blow away the pyo3-log cache so that it reloads the configuration.
     reset_logging_config()