Fix starting with -c "" and add test.

Fixes #1169.

qutebrowser/config/configtypes.py

@@ -1269,8 +1269,16 @@ class UserStyleSheet(File):
     def transform(self, value):
         if not value:
             return None
+
+        if standarddir.config() is None:
+            # We can't call super().transform() here as this counts on the
+            # validation previously ensuring that we don't have a relative path
+            # when starting with -c "".
+            path = None
+        else:
             path = super().transform(value)
-        if os.path.exists(path):
+
+        if path is not None and os.path.exists(path):
             return QUrl.fromLocalFile(path)
         else:
             data = base64.b64encode(value.encode('utf-8')).decode('ascii')

tests/integration/test_cmdline_args.py

@@ -0,0 +1,53 @@
+# vim: ft=python fileencoding=utf-8 sts=4 sw=4 et:
+
+# Copyright 2016 Florian Bruhin (The Compiler) <mail@qutebrowser.org>
+#
+# This file is part of qutebrowser.
+#
+# qutebrowser is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# qutebrowser is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with qutebrowser.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Test starting qutebrowser with various commandline arguments."""
+
+import pytest
+
+
+@pytest.mark.linux
+def test_no_config(tmpdir, quteproc_new):
+    """Test starting with -c "".
+
+    We can't run --basedir or --temp-basedir to reproduce this, so we mess with
+    XDG_*_DIR to get things relocated.
+    """
+    data_dir = tmpdir / 'data'
+    config_dir = tmpdir / 'config'
+    runtime_dir = tmpdir / 'runtime'
+    cache_dir = tmpdir / 'cache'
+
+    runtime_dir.ensure(dir=True)
+    runtime_dir.chmod(0o700)
+
+    (data_dir / 'qutebrowser' / 'state').write_text(
+        '[general]\nquickstart-done = 1', encoding='utf-8', ensure=True)
+
+    env = {
+        'XDG_DATA_HOME': str(data_dir),
+        'XDG_CONFIG_HOME': str(config_dir),
+        'XDG_RUNTIME_DIR': str(runtime_dir),
+        'XDG_CACHE_HOME': str(cache_dir),
+    }
+
+    args = ['--debug', '--no-err-windows', '-c', '', 'about:blank']
+    quteproc_new.start(args, env=env)
+    quteproc_new.send_cmd(':quit')
+    quteproc_new.wait_for_quit()