chore: review fixes, add test for unordered messages

Author: ttypic

ably/__init__.py

@@ -8,7 +8,7 @@
 from ably.types.options import Options, VCDiffDecoder
 from ably.util.crypto import CipherParams
 from ably.util.exceptions import AblyException, AblyAuthException, IncompatibleClientIdException
-from ably.vcdiff.ably_vcdiff_decoder import AblyVCDiffDecoder
+from ably.vcdiff.default_vcdiff_decoder import AblyVCDiffDecoder
 
 import logging
 

ably/types/options.py

@@ -9,6 +9,16 @@
 
 
 class VCDiffDecoder(ABC):
+    """
+    The VCDiffDecoder class defines the interface for delta decoding operations.
+
+    This class serves as an abstract base class for implementing delta decoding
+    algorithms, which are used to generate target bytes from compressed delta
+    bytes and base bytes. Subclasses of this class should implement the decode
+    method to handle the specifics of delta decoding. The decode method typically
+    takes a delta bytes and base bytes as input and returns the decoded output.
+
+    """
     @abstractmethod
     def decode(self, delta: bytes, base: bytes) -> bytes:
         pass

ably/vcdiff/ably_vcdiff_decoder.py renamed to ably/vcdiff/default_vcdiff_decoder.py

@@ -8,7 +8,7 @@ per-file-ignores =
     # imported but unused
     __init__.py: F401
 # Exclude virtual environment check
-exclude = .venv,venv,env,.env,.git,__pycache__,.pytest_cache,build,dist,*.egg-info
+exclude = .venv,venv,env,.env,.git,__pycache__,.pytest_cache,build,dist,*.egg-info,ably/sync,test/ably/sync
 
 [tool:pytest]
 #log_level = DEBUG

setup.cfg

@@ -182,3 +182,44 @@ def on_message(message):
                 assert expected_message == actual_message, f"Check message.data for message {expected_message}"
         finally:
             await ably.close()
+
+    async def test_delta_message_out_of_order(self):
+        test_vcdiff_decoder = MockVCDiffDecoder()
+        ably = await TestApp.get_ably_realtime(vcdiff_decoder=test_vcdiff_decoder)
+
+        try:
+            await asyncio.wait_for(ably.connection.once_async(ConnectionState.CONNECTED), timeout=5)
+            channel = ably.channels.get('delta_plugin_out_of_order', ChannelOptions(params={'delta': 'vcdiff'}))
+            await channel.attach()
+            message_waiters = [WaitableEvent(), WaitableEvent()]
+            messages_received = []
+            counter = 0
+
+            def on_message(message):
+                nonlocal counter
+                messages_received.append(message.data)
+                message_waiters[counter].finish()
+                counter += 1
+
+            await channel.subscribe(on_message)
+            await channel.publish("1", self.test_data[0])
+            await message_waiters[0].wait(timeout=30)
+
+            attaching_reason = None
+
+            def on_attaching(state_change):
+                nonlocal attaching_reason
+                attaching_reason = state_change.reason
+
+            channel.on('attaching', on_attaching)
+
+            object.__getattribute__(channel, '_RealtimeChannel__decoding_context').last_message_id = 'fake_id'
+            await channel.publish("2", self.test_data[1])
+            await message_waiters[1].wait(timeout=30)
+            assert test_vcdiff_decoder.number_of_calls == 0, "Check that no delta message was decoded"
+            assert self._equals(messages_received[0], self.test_data[0]), "Check message.data for message 1"
+            assert self._equals(messages_received[1], self.test_data[1]), "Check message.data for message 2"
+            assert attaching_reason.code == 40018, "Check error code passed through per RTL18c"
+
+        finally:
+            await ably.close()