fix: use stacklevel=2 in AssignRequest deprecation warning

stacklevel=3 pointed at the wrong caller frame when encode_body()
was called directly (e.g. not via Message.encode()). stacklevel=2
is the conventional Python default and correctly points at the
immediate caller of encode_body() in all call paths.

Closes #153.

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

Author: antoineleclair

src/dqlitewire/messages/requests.py

@@ -446,7 +446,7 @@ def encode_body(self) -> bytes:
                 "(1-word body). Modern dqlite servers and the Go client always send "
                 "both node_id and role. Use role=0 (VOTER) for equivalent behavior.",
                 DeprecationWarning,
-                stacklevel=3,
+                stacklevel=2,
             )
         return result
 

tests/test_messages_requests.py

@@ -365,6 +365,18 @@ def test_encode_without_role_emits_deprecation_warning(self) -> None:
             assert issubclass(w[0].category, DeprecationWarning)
             assert "legacy" in str(w[0].message).lower() or "promote" in str(w[0].message).lower()
 
+    def test_encode_without_role_warning_points_at_encode_body_caller(self) -> None:
+        """153: stacklevel should point at the caller of encode_body()."""
+        import warnings
+
+        msg = AssignRequest(node_id=1)
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter("always")
+            # Call encode_body() directly — the warning should point here.
+            msg.encode_body()
+            assert len(w) == 1
+            assert w[0].filename == __file__
+
     def test_encode_with_role_no_warning(self) -> None:
         """Encoding AssignRequest with role should not warn."""
         import warnings