Fix crash of :debug-log-filter when --filter wasn't given

There was no `LogFilter`. The fix is to always initialize a
`LogFilter()` with `None`. as the "filter".

Fixes #2303.

CHANGELOG.asciidoc

@@ -52,6 +52,7 @@ Fixed
 - Crash when pressing ctrl-c while a config error is shown
 - Crash when the key config isn't writable
 - Crash when unbinding an unbound key in the key config
+- Crash when using `:debug-log-filter` when `--filter` wasn't given on startup.
 - Various rare crashes
 
 v0.10.1

qutebrowser/misc/utilcmds.py

@@ -295,13 +295,16 @@ def debug_log_filter(filters: str):
     Args:
         filters: A comma separated list of logger names.
     """
-    if set(filters.split(',')).issubset(log.LOGGER_NAMES):
+    if not set(filters.split(',')).issubset(log.LOGGER_NAMES):
-        log.console_filter.names = filters.split(',')
-    else:
         raise cmdexc.CommandError("filters: Invalid value {} - expected one "
                                   "of: {}".format(filters,
                                                   ', '.join(log.LOGGER_NAMES)))
 
+    if log.console_filter is None:
+        raise cmdexc.CommandError("No log.console_filter. Not attached "
+                                  "to a console?")
+    log.console_filter.names = filters.split(',')
+
 
 @cmdutils.register()
 @cmdutils.argument('current_win_id', win_id=True)

qutebrowser/utils/log.py

@@ -182,9 +182,10 @@ def init_log(args):
     root = logging.getLogger()
     global console_filter
     if console is not None:
+        console_filter = LogFilter(None)
         if args.logfilter is not None:
-            console_filter = LogFilter(args.logfilter.split(','))
+            console_filter.names = args.logfilter.split(',')
-            console.addFilter(console_filter)
+        console.addFilter(console_filter)
         root.addHandler(console)
     if ram is not None:
         root.addHandler(ram)

tests/end2end/features/utilcmds.feature

@@ -164,3 +164,7 @@ Feature: Miscellaneous utility commands exposed to the user.
     Scenario: Using debug-log-filter with invalid filter
         When I run :debug-log-filter blah
         Then the error "filters: Invalid value blah - expected one of: statusbar, *" should be shown
+
+    Scenario: Using debug-log-filter
+        When I run :debug-log-filter webview
+        Then no crash should happen