Add transaction handling to connection context manager __exit__

Commit on clean exit and rollback on exception, following the
convention used by psycopg2 and sqlite3. Errors from commit/rollback
are suppressed since the connection is closing regardless.

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

Author: antoineleclair

src/dqlitedbapi/aio/connection.py

@@ -100,5 +100,13 @@ async def __aenter__(self) -> "AsyncConnection":
         await self.connect()
         return self
 
-    async def __aexit__(self, *args: Any) -> None:
-        await self.close()
+    async def __aexit__(self, exc_type: type[BaseException] | None, *args: Any) -> None:
+        try:
+            if exc_type is None:
+                await self.commit()
+            else:
+                await self.rollback()
+        except Exception:
+            pass
+        finally:
+            await self.close()

src/dqlitedbapi/connection.py

@@ -128,5 +128,13 @@ def cursor(self) -> Cursor:
     def __enter__(self) -> "Connection":
         return self
 
-    def __exit__(self, *args: Any) -> None:
-        self.close()
+    def __exit__(self, exc_type: type[BaseException] | None, *args: Any) -> None:
+        try:
+            if exc_type is None:
+                self.commit()
+            else:
+                self.rollback()
+        except Exception:
+            pass
+        finally:
+            self.close()

tests/integration/test_context_manager.py

@@ -0,0 +1,56 @@
+"""Integration tests for connection context manager transaction handling."""
+
+import pytest
+
+from dqlitedbapi import connect
+
+
+@pytest.mark.integration
+class TestContextManagerTransactions:
+    def test_context_manager_commits_on_clean_exit(self, cluster_address: str) -> None:
+        """Connection context manager should commit on clean exit."""
+        with connect(cluster_address, database="test_ctx_commit2") as conn:
+            cursor = conn.cursor()
+            cursor.execute("DROP TABLE IF EXISTS ctx_test")
+            cursor.execute("CREATE TABLE ctx_test (id INTEGER PRIMARY KEY, val TEXT)")
+            cursor.execute("BEGIN")
+            cursor.execute("INSERT INTO ctx_test (id, val) VALUES (1, 'committed')")
+            # __exit__ should commit
+
+        # Verify data persisted
+        with connect(cluster_address, database="test_ctx_commit2") as conn:
+            cursor = conn.cursor()
+            cursor.execute("SELECT val FROM ctx_test WHERE id = 1")
+            row = cursor.fetchone()
+            assert row is not None
+            assert row[0] == "committed"
+            cursor.execute("DROP TABLE ctx_test")
+
+    def test_context_manager_rolls_back_on_exception(self, cluster_address: str) -> None:
+        """Connection context manager should rollback on exception."""
+        # Set up a table with known state
+        with connect(cluster_address, database="test_ctx_rollback2") as conn:
+            cursor = conn.cursor()
+            cursor.execute("DROP TABLE IF EXISTS ctx_rb_test")
+            cursor.execute("CREATE TABLE ctx_rb_test (id INTEGER PRIMARY KEY, val TEXT)")
+            cursor.execute("INSERT INTO ctx_rb_test (id, val) VALUES (1, 'original')")
+
+        # Update inside an explicit transaction, then raise
+        with (
+            pytest.raises(ValueError, match="simulated error"),
+            connect(cluster_address, database="test_ctx_rollback2") as conn,
+        ):
+            cursor = conn.cursor()
+            cursor.execute("BEGIN")
+            cursor.execute("UPDATE ctx_rb_test SET val = 'changed' WHERE id = 1")
+            raise ValueError("simulated error")
+            # __exit__ should rollback
+
+        # Verify original value is preserved (rolled back)
+        with connect(cluster_address, database="test_ctx_rollback2") as conn:
+            cursor = conn.cursor()
+            cursor.execute("SELECT val FROM ctx_rb_test WHERE id = 1")
+            row = cursor.fetchone()
+            assert row is not None
+            assert row[0] == "original"
+            cursor.execute("DROP TABLE ctx_rb_test")