log: Handle JSONLogger in change_console_formatter

Fixes #6482

(cherry picked from commit 40477e826c9ec73a8f99177df645094be3ef5ed3)

2 files changed, 20 insertions, 5 deletions

diff --git a/qutebrowser/utils/log.py b/qutebrowser/utils/log.py
index b6f1f3e9b..2fb64eddd 100644
--- a/qutebrowser/utils/log.py
+++ b/qutebrowser/utils/log.py
@@ -363,12 +363,16 @@ def change_console_formatter(level: int) -> None:
         level: The numeric logging level
     """
     assert console_handler is not None
+    old_formatter = console_handler.formatter
 
-    old_formatter = cast(ColoredFormatter, console_handler.formatter)
-    console_fmt = get_console_format(level)
-    console_formatter = ColoredFormatter(console_fmt, DATEFMT, '{',
-                                         use_colors=old_formatter.use_colors)
-    console_handler.setFormatter(console_formatter)
+    if isinstance(old_formatter, ColoredFormatter):
+        console_fmt = get_console_format(level)
+        console_formatter = ColoredFormatter(
+            console_fmt, DATEFMT, '{', use_colors=old_formatter.use_colors)
+        console_handler.setFormatter(console_formatter)
+    else:
+        # Same format for all levels
+        assert isinstance(old_formatter, JSONFormatter), old_formatter
 
 
 def qt_message_handler(msg_type: QtCore.QtMsgType,
diff --git a/tests/end2end/test_invocations.py b/tests/end2end/test_invocations.py
index 1ce22b7ea..076ebb2bd 100644
--- a/tests/end2end/test_invocations.py
+++ b/tests/end2end/test_invocations.py
@@ -743,3 +743,14 @@ def test_unavailable_backend(request, quteproc_new):
         message=('*qutebrowser tried to start with the Qt* backend but failed '
                  'because * could not be imported.*'))
     line.expected = True
+
+
+def test_json_logging_without_debug(request, quteproc_new):
+    args = _base_args(request.config) + ['--temp-basedir', ':quit']
+    args.remove('--debug')
+    args.remove('about:blank')  # interfers with :quit at the end
+
+    quteproc_new.exit_expected = True
+    quteproc_new.start(args)
+    assert not quteproc_new.is_running()
+    assert not quteproc_new.captured_log