Classify InterfaceError("Connection is closed") as a disconnect

After the underlying DBAPI connection is closed out of band (pool
invalidate, cluster membership change, explicit close), the next
statement raises dqlitedbapi.InterfaceError("Connection is closed").
is_disconnect was only testing OperationalError subtypes, so the pool
did NOT invalidate the stale slot and the error kept surfacing on
every check-out. Add a narrow InterfaceError branch keyed on the
"connection is closed" / "cursor is closed" messages — programming-
error InterfaceErrors (e.g. arraysize validation) stay unclassified.

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

Author: antoineleclair

src/sqlalchemydqlite/base.py

@@ -296,6 +296,16 @@ def is_disconnect(self, e: Any, connection: Any, cursor: Any) -> bool:
         # DNS, connect refused) surface as these stdlib types.
         if isinstance(e, (ConnectionError, BrokenPipeError, TimeoutError, OSError)):
             return True
+        # ``dqlitedbapi.Connection`` / ``Cursor`` raise ``InterfaceError``
+        # when operated on after ``close()``; match the narrow
+        # "closed" substring so programming-error InterfaceErrors (e.g.
+        # setinputsizes on a closed cursor) are NOT classified as
+        # disconnect. The do_ping path already catches InterfaceError
+        # for the same reason.
+        if isinstance(e, _dbapi_exc.InterfaceError):
+            message = str(e).lower()
+            if "connection is closed" in message or "cursor is closed" in message:
+                return True
         # Leader-change error codes signal that the connection is useless
         # even though it's TCP-alive.
         for err in (_dbapi_exc.OperationalError, _client_exc.OperationalError):

tests/test_dialect.py

@@ -319,6 +319,35 @@ def test_is_defined_on_dialect(self) -> None:
             "DqliteDialect must override is_disconnect"
         )
 
+    def test_recognizes_interface_error_connection_closed(self) -> None:
+        """An InterfaceError raised after the underlying DBAPI connection
+        was closed (e.g. pool invalidate, cluster membership change)
+        must be classified as disconnect so the pool recycles the slot.
+        """
+        import dqlitedbapi.exceptions
+
+        dialect = DqliteDialect()
+        e = dqlitedbapi.exceptions.InterfaceError("Connection is closed")
+        assert dialect.is_disconnect(e, None, None) is True
+
+    def test_recognizes_interface_error_cursor_closed(self) -> None:
+        import dqlitedbapi.exceptions
+
+        dialect = DqliteDialect()
+        e = dqlitedbapi.exceptions.InterfaceError("Cursor is closed")
+        assert dialect.is_disconnect(e, None, None) is True
+
+    def test_does_not_flag_other_interface_errors(self) -> None:
+        """Narrowly-worded programming-error InterfaceErrors (e.g.
+        `arraysize must be positive`) must NOT route through the
+        disconnect path.
+        """
+        import dqlitedbapi.exceptions
+
+        dialect = DqliteDialect()
+        e = dqlitedbapi.exceptions.InterfaceError("arraysize must be positive")
+        assert dialect.is_disconnect(e, None, None) is False
+
 
 class TestIsolationLevel:
     def test_set_isolation_level_warns_on_unsupported(self) -> None: