feat: add PEP 249 optional messages attribute

Add a mutable list attribute ``messages`` on Connection, AsyncConnection,
Cursor, and AsyncCursor as required by PEP 249's optional extensions.
Currently no driver path appends to the list; callers can rely on the
attribute existing and being mutable.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/dqlitedbapi/aio/connection.py

@@ -47,6 +47,8 @@ def __init__(
         # glue code before any loop exists).
         self._connect_lock: asyncio.Lock | None = None
         self._op_lock: asyncio.Lock | None = None
+        # PEP 249 optional extension; see Connection.messages.
+        self.messages: list[tuple[type, Any]] = []
 
     def _ensure_locks(self) -> tuple[asyncio.Lock, asyncio.Lock]:
         """Lazy-create the asyncio locks on the currently-running loop."""

src/dqlitedbapi/aio/cursor.py

@@ -30,6 +30,8 @@ def __init__(self, connection: "AsyncConnection") -> None:
         self._row_index = 0
         self._closed = False
         self._lastrowid: int | None = None
+        # PEP 249 optional extension; see Cursor.messages.
+        self.messages: list[tuple[type, Any]] = []
 
     @property
     def connection(self) -> "AsyncConnection":

src/dqlitedbapi/connection.py

@@ -91,6 +91,9 @@ def __init__(
         self._op_lock = threading.Lock()
         self._connect_lock: asyncio.Lock | None = None
         self._creator_thread = threading.get_ident()
+        # PEP 249 optional extension. No driver path currently appends
+        # here; callers can rely on the attribute existing.
+        self.messages: list[tuple[type, Any]] = []
         # 1-element list (mutable, captured by the finalizer) that
         # close() flips to True. Using a list avoids the finalizer
         # closing over ``self`` and preventing GC.

src/dqlitedbapi/cursor.py

@@ -134,6 +134,10 @@ def __init__(self, connection: "Connection") -> None:
         self._row_index = 0
         self._closed = False
         self._lastrowid: int | None = None
+        # PEP 249 optional extension. Currently no driver path appends
+        # to this list; it's here so consumers can rely on the
+        # attribute existing and being mutable.
+        self.messages: list[tuple[type, Any]] = []
 
     @property
     def connection(self) -> "Connection":

tests/test_messages_attribute.py

@@ -0,0 +1,34 @@
+"""PEP 249 optional extension: Connection.messages / Cursor.messages."""
+
+from dqlitedbapi import Connection
+from dqlitedbapi.aio import AsyncConnection
+from dqlitedbapi.aio.cursor import AsyncCursor
+from dqlitedbapi.cursor import Cursor
+
+
+def test_connection_messages_attribute() -> None:
+    conn = Connection("localhost:9001")
+    assert isinstance(conn.messages, list)
+    assert conn.messages == []
+    # Must be mutable.
+    conn.messages.append((RuntimeError, "x"))
+
+
+def test_cursor_messages_attribute() -> None:
+    conn = Connection("localhost:9001")
+    cursor = Cursor(conn)
+    assert isinstance(cursor.messages, list)
+    assert cursor.messages == []
+
+
+def test_async_connection_messages_attribute() -> None:
+    conn = AsyncConnection("localhost:9001")
+    assert isinstance(conn.messages, list)
+    assert conn.messages == []
+
+
+def test_async_cursor_messages_attribute() -> None:
+    conn = AsyncConnection("localhost:9001")
+    cursor = AsyncCursor(conn)
+    assert isinstance(cursor.messages, list)
+    assert cursor.messages == []