gh-118221: Always use the default row factory in sqlite3.iterdump() (#118223)

sqlite3.iterdump() depends on the row factory returning resulting rows
as tuples; it will fail with custom row factories like for example a
dict factory.

With this commit, we explicitly reset the row factory of the cursor used
by iterdump(), so we always get predictable results. This does not
affect the row factory of the parent connection.

Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

Lib/sqlite3/dump.py

@@ -26,6 +26,7 @@ def _iterdump(connection, *, filter=None):
 
     writeable_schema = False
     cu = connection.cursor()
+    cu.row_factory = None  # Make sure we get predictable results.
     # Disable foreign key constraints, if there is any foreign key violation.
     violations = cu.execute("PRAGMA foreign_key_check").fetchall()
     if violations:

Lib/test/test_sqlite3/test_dump.py

@@ -190,6 +190,21 @@ def __getitem__(self, index):
         got = list(self.cx.iterdump())
         self.assertEqual(expected, got)
 
+    def test_dump_custom_row_factory(self):
+        # gh-118221: iterdump should be able to cope with custom row factories.
+        def dict_factory(cu, row):
+            fields = [col[0] for col in cu.description]
+            return dict(zip(fields, row))
+
+        self.cx.row_factory = dict_factory
+        CREATE_TABLE = "CREATE TABLE test(t);"
+        expected = ["BEGIN TRANSACTION;", CREATE_TABLE, "COMMIT;"]
+
+        self.cu.execute(CREATE_TABLE)
+        actual = list(self.cx.iterdump())
+        self.assertEqual(expected, actual)
+        self.assertEqual(self.cx.row_factory, dict_factory)
+
     def test_dump_virtual_tables(self):
         # gh-64662
         expected = [

Misc/NEWS.d/next/Library/2024-04-24-12-29-33.gh-issue-118221.2k_bac.rst

@@ -0,0 +1,2 @@
+Fix a bug where :func:`sqlite3.iterdump` could fail if a custom :attr:`row
+factory <sqlite3.Connection.row_factory>` was used. Patch by Erlend Aasland.