Drop underscore prefix on LEADER_ERROR_CODES re-import

The wire layer publishes LEADER_ERROR_CODES as a public constant.
Both consumers (pool.py and connection.py) imported it under the
private alias _LEADER_ERROR_CODES. The underscore was overprotective:
the constant is intentionally re-imported from a public name, and
neither module re-exports it via __all__. The alias gave a misleading
"private to this module" cue to readers.

Drop the alias in both modules; usages now read LEADER_ERROR_CODES
directly. Pin the cross-layer identity contract via a new test that
asserts LEADER_ERROR_CODES is the same object in pool.py,
connection.py, and the wire layer.

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

Author: antoineleclair

src/dqliteclient/connection.py

@@ -25,7 +25,7 @@
 )
 from dqlitewire import DEFAULT_MAX_CONTINUATION_FRAMES as _DEFAULT_MAX_CONTINUATION_FRAMES
 from dqlitewire import DEFAULT_MAX_TOTAL_ROWS as _DEFAULT_MAX_TOTAL_ROWS
-from dqlitewire import LEADER_ERROR_CODES as _LEADER_ERROR_CODES
+from dqlitewire import LEADER_ERROR_CODES
 from dqlitewire import SQLITE_BUSY as _SQLITE_BUSY
 from dqlitewire import TX_AUTO_ROLLBACK_PRIMARY_CODES as _TX_AUTO_ROLLBACK_PRIMARY_CODES
 from dqlitewire import primary_sqlite_code as _primary_sqlite_code
@@ -65,7 +65,7 @@
 #   * SQLITE_ABORT (4) — operation aborted, e.g. via sqlite3_interrupt.
 #   * SQLITE_INTERRUPT (9) — query interrupted via INTERRUPT.
 #   * SQLITE_IOERR (10) — and most extended IOERR variants (the leader-
-#     change variants are caught earlier as ``_LEADER_ERROR_CODES`` and
+#     change variants are caught earlier as ``LEADER_ERROR_CODES`` and
 #     trigger a full ``_invalidate`` instead).
 #   * SQLITE_CORRUPT (11).
 #   * SQLITE_FULL (13).
@@ -754,7 +754,7 @@ async def _connect_impl(self) -> None:
             self._invalidation_cause = None
         except OperationalError as e:
             await self._abort_protocol()
-            if e.code in _LEADER_ERROR_CODES:
+            if e.code in LEADER_ERROR_CODES:
                 # Leader-change errors during OPEN are transport-level
                 # problems — the caller needs to reconnect elsewhere, not
                 # treat this as a SQL error.
@@ -1135,7 +1135,7 @@ async def _run_protocol[T](self, fn: Callable[[DqliteProtocol, int], Awaitable[T
             self._invalidate(e)
             raise
         except OperationalError as e:
-            if e.code in _LEADER_ERROR_CODES:
+            if e.code in LEADER_ERROR_CODES:
                 self._invalidate(e)
             elif _primary_sqlite_code(e.code) in _TX_AUTO_ROLLBACK_PRIMARY_CODES:
                 # Server-side SQLite engine auto-rolled-back the

src/dqliteclient/pool.py

@@ -29,7 +29,7 @@
 from dqlitewire import (
     DEFAULT_MAX_TOTAL_ROWS as _DEFAULT_MAX_TOTAL_ROWS,
 )
-from dqlitewire import LEADER_ERROR_CODES as _LEADER_ERROR_CODES
+from dqlitewire import LEADER_ERROR_CODES
 
 __all__ = ["ConnectionPool"]
 
@@ -1036,7 +1036,7 @@ async def _reset_connection(self, conn: DqliteConnection) -> bool:
                 # DEBUG) from genuine server failure (latent bug or
                 # server fault — WARNING with traceback).
                 code = getattr(exc, "code", None)
-                if code in _LEADER_ERROR_CODES:
+                if code in LEADER_ERROR_CODES:
                     logger.debug(
                         "pool: dropping connection %s after leader-class "
                         "ROLLBACK failure (code=%s)",

tests/test_leader_error_codes_identity.py

@@ -0,0 +1,22 @@
+"""Pin: ``LEADER_ERROR_CODES`` is the single source of truth for the
+leader-change SQLite extended codes, owned by ``dqlitewire`` and
+imported as-is by ``dqliteclient``. Identity equality is the
+contract — a future SA-only override or accidental local copy would
+fail this test.
+"""
+
+from __future__ import annotations
+
+
+def test_dqliteclient_uses_wire_leader_error_codes_identity() -> None:
+    # The constants live inside each module but are deliberately NOT
+    # in ``__all__`` (they're re-imports of a wire-layer public
+    # constant, not the module's own public surface). Direct
+    # attribute access works at runtime; the mypy ignores reflect
+    # the re-import-without-export pattern.
+    import dqliteclient.connection as _conn_mod
+    import dqliteclient.pool as _pool_mod
+    from dqlitewire import LEADER_ERROR_CODES as wire_codes
+
+    assert _pool_mod.LEADER_ERROR_CODES is wire_codes  # type: ignore[attr-defined]
+    assert _conn_mod.LEADER_ERROR_CODES is wire_codes  # type: ignore[attr-defined]