fix: clear _continuation_expected on failure during ROWS continuation

decode_continuation() now sets _continuation_expected to False before
raising ProtocolError when receiving a FailureResponse or unexpected
message type. Previously the flag stayed True, which was semantically
wrong and fragile if poison-on-error behavior were ever relaxed.

Closes #103

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/dqlitewire/codec.py

@@ -288,10 +288,12 @@ def decode_continuation(self) -> RowsResponse | None:
 
             if header.msg_type == ResponseType.FAILURE:
                 failure = FailureResponse.decode_body(body, schema=header.schema)
+                self._continuation_expected = False
                 raise ProtocolError(
                     f"Server error during ROWS continuation: [{failure.code}] {failure.message}"
                 )
             if header.msg_type != ResponseType.ROWS:
+                self._continuation_expected = False
                 raise ProtocolError(
                     f"Expected ROWS continuation (type {ResponseType.ROWS}), "
                     f"got type {header.msg_type}"

tests/test_codec.py

@@ -1586,6 +1586,32 @@ def test_failure_during_continuation_poisons(self) -> None:
 
         assert decoder.is_poisoned
 
+    def test_failure_during_continuation_clears_flag(self) -> None:
+        """103: _continuation_expected must be False after FailureResponse."""
+        from dqlitewire.constants import ValueType
+        from dqlitewire.exceptions import ProtocolError
+        from dqlitewire.messages.responses import FailureResponse, RowsResponse
+
+        initial = RowsResponse(
+            column_names=["id"],
+            column_types=[ValueType.INTEGER],
+            rows=[[1]],
+            has_more=True,
+        )
+        failure = FailureResponse(code=5, message="disk I/O error")
+
+        decoder = MessageDecoder(is_request=False)
+        decoder.feed(initial.encode() + failure.encode())
+
+        msg = decoder.decode()
+        assert isinstance(msg, RowsResponse) and msg.has_more
+
+        with pytest.raises(ProtocolError, match="disk I/O error"):
+            decoder.decode_continuation()
+
+        # The continuation flag must be cleared even though the buffer is poisoned
+        assert not decoder._continuation_expected
+
     def test_chained_continuations_part_part_done(self) -> None:
         """084: three frames — initial(PART) + cont(PART) + cont(DONE)."""
         from dqlitewire.constants import ValueType