Check that target backup DB is not in transaction

This is needed for SQLite < 3.8.7.
berkerpeksag · Mar 10, 2018 · Jul 28, 2016 · Jul 28, 2016 · Mar 1, 2017 · Mar 1, 2017
commit 4bd0b3e074d9230d34fee1ba5b6a4dfbcd82a374
diff --git a/Lib/sqlite3/test/backup.py b/Lib/sqlite3/test/backup.py
@@ -135,6 +135,16 @@ def CheckBackupToOtherConnection(self):
         self.assertEqual(result[0][0], 3)
         self.assertEqual(result[1][0], 4)
 
+    def CheckBackupToOtherConnectionInTransaction(self):
+        dx = sqlite.connect(':memory:')
+        dx.execute('CREATE TABLE bar (key INTEGER)')
+        dx.executemany('INSERT INTO bar (key) VALUES (?)', [(3,), (4,)])
+        try:
+            with self.assertRaises(sqlite.OperationalError):
+                self.cx.backup(dx)
+        finally:
+            dx.rollback()
+
 def suite():
     return unittest.TestSuite(unittest.makeSuite(BackupTests, "Check"))
 

diff --git a/Modules/_sqlite/connection.c b/Modules/_sqlite/connection.c
@@ -1508,6 +1508,14 @@ pysqlite_connection_backup(pysqlite_Connection* self, PyObject* args, PyObject*
             PyErr_SetString(PyExc_ValueError, "target cannot be the same connection instance");
             goto finally;
         }
+#if SQLITE_VERSION_NUMBER < 3008007
+        /* Since 3.8.7 this is already done, per commit
+           https://www.sqlite.org/src/info/169b5505498c0a7e */
+        if (!sqlite3_get_autocommit(((pysqlite_Connection*)target)->db)) {
+            PyErr_SetString(pysqlite_OperationalError, "target is in transaction");
+            goto finally;
+        }
+#endif
         filename = NULL;
         bckconn = ((pysqlite_Connection*)target)->db;
     }