Fix for cannot change into wal mode from within a transaction

sqlite_utils/db.py

@@ -28,6 +28,7 @@ from typing import (
     cast,
     Any,
     Callable,
+    ContextManager,
     Dict,
     Generator,
     Iterable,
@@ -346,6 +347,25 @@ class Database:
         "Close the SQLite connection, and the underlying database file"
         self.conn.close()
 
+    @contextlib.contextmanager
+    def ensure_autocommit_off(self):
+        """
+        Ensure autocommit is off for this database connection.
+
+        Example usage::
+
+            with db.ensure_autocommit_off():
+                # do stuff here
+
+        This will reset to the previous autocommit state at the end of the block.
+        """
+        old_isolation_level = self.conn.isolation_level
+        try:
+            self.conn.isolation_level = None
+            yield
+        finally:
+            self.conn.isolation_level = old_isolation_level
+
     @contextlib.contextmanager
     def tracer(self, tracer: Optional[Callable] = None):
         """
@@ -662,12 +682,14 @@ class Database:
         Sets ``journal_mode`` to ``'wal'`` to enable Write-Ahead Log mode.
         """
         if self.journal_mode != "wal":
-            self.execute("PRAGMA journal_mode=wal;")
+            with self.ensure_autocommit_off():
+                self.execute("PRAGMA journal_mode=wal;")
 
     def disable_wal(self):
         "Sets ``journal_mode`` back to ``'delete'`` to disable Write-Ahead Log mode."
         if self.journal_mode != "delete":
-            self.execute("PRAGMA journal_mode=delete;")
+            with self.ensure_autocommit_off():
+                self.execute("PRAGMA journal_mode=delete;")
 
     def _ensure_counts_table(self):
         with self.conn:

tests/test_cli.py

@@ -1429,7 +1429,7 @@ def test_enable_wal():
             db = Database(dbname)
             db["t"].create({"pk": int}, pk="pk")
             assert db.journal_mode == "delete"
-        result = runner.invoke(cli.cli, ["enable-wal"] + dbs)
+        result = runner.invoke(cli.cli, ["enable-wal"] + dbs, catch_exceptions=False)
         assert 0 == result.exit_code
         for dbname in dbs:
             db = Database(dbname)