fix #354

bumble/gatt_client.py

@@ -207,11 +207,11 @@ def on_change(value):
 
         return await self.client.subscribe(self, subscriber, prefer_notify)
 
-    async def unsubscribe(self, subscriber=None):
+    async def unsubscribe(self, subscriber=None, force=False):
         if subscriber in self.subscribers:
             subscriber = self.subscribers.pop(subscriber)
 
-        return await self.client.unsubscribe(self, subscriber)
+        return await self.client.unsubscribe(self, subscriber, force)
 
     def __str__(self) -> str:
         return (
@@ -262,10 +262,8 @@ def __init__(self, connection: Connection) -> None:
         self.request_semaphore = asyncio.Semaphore(1)
         self.pending_request = None
         self.pending_response = None
-        self.notification_subscribers = (
-            {}
-        )  # Notification subscribers, by attribute handle
-        self.indication_subscribers = {}  # Indication subscribers, by attribute handle
+        self.notification_subscribers = {}  # Subscriber set, by attribute handle
+        self.indication_subscribers = {}  # Subscriber set, by attribute handle
         self.services = []
         self.cached_values = {}
 
@@ -836,6 +834,7 @@ async def subscribe(
         subscriber_set = subscribers.setdefault(characteristic.handle, set())
         if subscriber is not None:
             subscriber_set.add(subscriber)
+
         # Add the characteristic as a subscriber, which will result in the
         # characteristic emitting an 'update' event when a notification or indication
         # is received
@@ -847,7 +846,14 @@ async def unsubscribe(
         self,
         characteristic: CharacteristicProxy,
         subscriber: Optional[Callable[[bytes], Any]] = None,
+        force: bool = False,
     ) -> None:
+        '''
+        Unsubscribe from a characteristic.
+
+        If `force` is True, this will write zeros to the CCCD when there are no
+        subscribers left, even if there were already no registered subscribers.
+        '''
         # If we haven't already discovered the descriptors for this characteristic,
         # do it now
         if not characteristic.descriptors_discovered:
@@ -861,25 +867,39 @@ async def unsubscribe(
             logger.warning('unsubscribing from characteristic with no CCCD descriptor')
             return
 
+        # Check if the characteristic has subscribers
+        if not (
+            characteristic.handle in self.notification_subscribers
+            or characteristic.handle in self.indication_subscribers
+        ):
+            if not force:
+                return
+
+        # Remove the subscriber(s)
         if subscriber is not None:
             # Remove matching subscriber from subscriber sets
             for subscriber_set in (
                 self.notification_subscribers,
                 self.indication_subscribers,
             ):
-                subscribers = subscriber_set.get(characteristic.handle, set())
-                if subscriber in subscribers:
+                if (
+                    subscribers := subscriber_set.get(characteristic.handle)
+                ) and subscriber in subscribers:
                     subscribers.remove(subscriber)
 
                     # Cleanup if we removed the last one
                     if not subscribers:
                         del subscriber_set[characteristic.handle]
         else:
-            # Remove all subscribers for this attribute from the sets!
+            # Remove all subscribers for this attribute from the sets
             self.notification_subscribers.pop(characteristic.handle, None)
             self.indication_subscribers.pop(characteristic.handle, None)
 
-        if not self.notification_subscribers and not self.indication_subscribers:
+        # Update the CCCD
+        if not (
+            characteristic.handle in self.notification_subscribers
+            or characteristic.handle in self.indication_subscribers
+        ):
             # No more subscribers left
             await self.write_value(cccd, b'\x00\x00', with_response=True)
 

tests/gatt_test.py

@@ -20,6 +20,7 @@
 import os
 import struct
 import pytest
+from unittest.mock import Mock, ANY
 
 from bumble.controller import Controller
 from bumble.gatt_client import CharacteristicProxy
@@ -763,6 +764,83 @@ def on_c3_update_3(value):  # for indicate
     assert not c3._called_3
 
 
+# -----------------------------------------------------------------------------
+@pytest.mark.asyncio
+async def test_unsubscribe():
+    [client, server] = LinkedDevices().devices[:2]
+
+    characteristic1 = Characteristic(
+        'FDB159DB-036C-49E3-B3DB-6325AC750806',
+        Characteristic.Properties.READ | Characteristic.Properties.NOTIFY,
+        Characteristic.READABLE,
+        bytes([1, 2, 3]),
+    )
+    characteristic2 = Characteristic(
+        '3234C4F4-3F34-4616-8935-45A50EE05DEB',
+        Characteristic.Properties.READ | Characteristic.Properties.NOTIFY,
+        Characteristic.READABLE,
+        bytes([1, 2, 3]),
+    )
+
+    service1 = Service(
+        '3A657F47-D34F-46B3-B1EC-698E29B6B829',
+        [characteristic1, characteristic2],
+    )
+    server.add_services([service1])
+
+    mock1 = Mock()
+    characteristic1.on('subscription', mock1)
+    mock2 = Mock()
+    characteristic2.on('subscription', mock2)
+
+    await client.power_on()
+    await server.power_on()
+    connection = await client.connect(server.random_address)
+    peer = Peer(connection)
+
+    await peer.discover_services()
+    await peer.discover_characteristics()
+    c = peer.get_characteristics_by_uuid(characteristic1.uuid)
+    assert len(c) == 1
+    c1 = c[0]
+    c = peer.get_characteristics_by_uuid(characteristic2.uuid)
+    assert len(c) == 1
+    c2 = c[0]
+
+    await c1.subscribe()
+    await async_barrier()
+    mock1.assert_called_once_with(ANY, True, False)
+
+    await c2.subscribe()
+    await async_barrier()
+    mock2.assert_called_once_with(ANY, True, False)
+
+    mock1.reset_mock()
+    await c1.unsubscribe()
+    await async_barrier()
+    mock1.assert_called_once_with(ANY, False, False)
+
+    mock2.reset_mock()
+    await c2.unsubscribe()
+    await async_barrier()
+    mock2.assert_called_once_with(ANY, False, False)
+
+    mock1.reset_mock()
+    await c1.unsubscribe()
+    await async_barrier()
+    mock1.assert_not_called()
+
+    mock2.reset_mock()
+    await c2.unsubscribe()
+    await async_barrier()
+    mock2.assert_not_called()
+
+    mock1.reset_mock()
+    await c1.unsubscribe(force=True)
+    await async_barrier()
+    mock1.assert_called_once_with(ANY, False, False)
+
+
 # -----------------------------------------------------------------------------
 @pytest.mark.asyncio
 async def test_mtu_exchange():
@@ -886,6 +964,7 @@ async def async_main():
     await test_read_write()
     await test_read_write2()
     await test_subscribe_notify()
+    await test_unsubscribe()
     await test_characteristic_encoding()
     await test_mtu_exchange()