Log an error when listeners are added that do not inherit from RecordUpdateListener (#1034)

bdraco · web-flow · commit ee071a12f31f · 2021-11-18T14:12:56.000-06:00
diff --git a/tests/test_handlers.py b/tests/test_handlers.py
@@ -1538,3 +1538,25 @@ async def test_future_answers_are_removed_on_send():
 
     # But the one we have not sent yet shoudl still go out later
     assert info2.dns_pointer() in outgoing_queue.queue[0].answers
+
+
+@pytest.mark.asyncio
+async def test_add_listener_warns_when_not_using_record_update_listener(caplog):
+    """Log when a listener is added that is not using RecordUpdateListener as a base class."""
+
+    aiozc = AsyncZeroconf(interfaces=['127.0.0.1'])
+    zc: Zeroconf = aiozc.zeroconf
+    updated = []
+
+    class MyListener:
+        """A RecordUpdateListener that does not implement update_records."""
+
+        def async_update_records(self, zc: 'Zeroconf', now: float, records: List[r.RecordUpdate]) -> None:
+            """Update multiple records in one shot."""
+            updated.extend(records)
+
+    zc.add_listener(MyListener(), None)
+    await asyncio.sleep(0)  # flush out any call soons
+    assert "listeners passed to async_add_listener must inherit from RecordUpdateListener" in caplog.text
+
+    await aiozc.async_close()
diff --git a/zeroconf/__init__.py b/zeroconf/__init__.py
@@ -63,7 +63,7 @@
 )
 from ._services.registry import ServiceRegistry  # noqa # import needed for backwards compat
 from ._services.types import ZeroconfServiceTypes
-from ._updates import RecordUpdate, RecordUpdateListener  # noqa # import needed for backwards compat
+from ._updates import RecordUpdate, RecordUpdateListener
 from ._utils.name import service_type_name  # noqa # import needed for backwards compat
 from ._utils.net import (  # noqa # import needed for backwards compat
     add_multicast_member,
@@ -94,6 +94,9 @@
     "ServiceStateChange",
     "IPVersion",
     "ZeroconfServiceTypes",
+    "RecordUpdate",
+    "RecordUpdateListener",
+    "current_time_millis",
     # Exceptions
     "Error",
     "AbstractMethodException",
diff --git a/zeroconf/_handlers.py b/zeroconf/_handlers.py
@@ -492,6 +492,12 @@ def async_add_listener(
 
         This function is not threadsafe and must be called in the eventloop.
         """
+        if not isinstance(listener, RecordUpdateListener):
+            log.error(
+                "listeners passed to async_add_listener must inherit from RecordUpdateListener;"
+                " In the future this will fail"
+            )
+
         self.listeners.append(listener)
 
         if question is None:
diff --git a/zeroconf/_updates.py b/zeroconf/_updates.py
@@ -36,6 +36,12 @@ class RecordUpdate(NamedTuple):
 
 
 class RecordUpdateListener:
+    """Base call for all record listeners.
+
+    All listeners passed to async_add_listener should use RecordUpdateListener
+    as a base class. In the future it will be required.
+    """
+
     def update_record(  # pylint: disable=no-self-use
         self, zc: 'Zeroconf', now: float, record: DNSRecord
     ) -> None:
diff --git a/zeroconf/_utils/time.py b/zeroconf/_utils/time.py
@@ -25,7 +25,11 @@
 
 
 def current_time_millis() -> float:
-    """Current system time in milliseconds"""
+    """Current time in milliseconds.
+
+    The current implemention uses `time.monotonic`
+    but may change in the future.
+    """
     return time.monotonic() * 1000
 
 
