Reject Python 3.12+ autocommit connections in the Database constructor

Connections created with sqlite3.connect(autocommit=True) make
commit() a documented no-op, and autocommit=False connections are
permanently inside a transaction - in both modes every write made
by this library appeared to work in-process but was silently
discarded when the connection closed. Database() now raises
TransactionError for these connections instead of losing data.

Tests are skipped on Python versions before 3.12, where the
autocommit parameter does not exist.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UnLnhsH25Nnv7LHhekUfPd
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Claude 2026-07-04 22:38:31 +00:00
commit bcd9a26560
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5 changed files with 51 additions and 1 deletions

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@ -95,6 +95,8 @@ Instead of a file path you can pass in an existing SQLite connection:
db = Database(sqlite3.connect("my_database.db"))
The connection must use Python's default transaction handling. Connections created with the Python 3.12+ ``sqlite3.connect(..., autocommit=True)`` or ``autocommit=False`` options are rejected with a ``sqlite_utils.db.TransactionError`` - see :ref:`python_api_transactions_modes`.
If you want to create an in-memory database, you can do so like this:
.. code-block:: python
@ -391,10 +393,14 @@ Two related safeguards to be aware of:
- ``db.enable_wal()`` and ``db.disable_wal()`` raise a ``sqlite_utils.db.TransactionError`` if called while a transaction is open, because changing the journal mode would commit it as a side effect.
- Closing the database - explicitly with ``db.close()``, or by exiting a ``with Database(...) as db:`` block - rolls back any transaction that is still open, see :ref:`python_api_close`.
.. _python_api_transactions_modes:
Supported connection modes
--------------------------
``db.atomic()`` and the automatic per-method transactions are designed for connections in Python's default transaction handling mode. Connections created with the Python 3.12+ ``sqlite3.connect(..., autocommit=True)`` or ``autocommit=False`` options are not supported, because ``commit()`` and ``rollback()`` behave differently on those connections.
``db.atomic()`` and the automatic per-method transactions require a connection in Python's default transaction handling mode. Passing a connection created with the Python 3.12+ ``sqlite3.connect(..., autocommit=True)`` or ``autocommit=False`` options to ``Database()`` raises a ``sqlite_utils.db.TransactionError``.
This is because ``commit()`` and ``rollback()`` behave differently on those connections - under ``autocommit=True`` they are documented no-ops - which would cause every write made by this library to be silently discarded when the connection closed, rather than failing loudly.
.. _python_api_table: