Implement config cache system

qutebrowser/config/configcache.py

@@ -0,0 +1,45 @@
+# vim: ft=python fileencoding=utf-8 sts=4 sw=4 et:
+
+# Copyright 2018 Jay Kamat <jaygkamat@gmail.com>
+#
+# 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/>.
+
+"""A 'high-performance' cache for the config system.
+
+Useful for areas which call out to the config system very frequently, DO NOT
+modify the value returned, and DO NOT require per-url settings.
+
+If any of these requirements are broken, you will get incorrect behavior.
+"""
+
+from qutebrowser.config import config
+
+
+class ConfigCache():
+
+    def __init__(self) -> None:
+        self.cache = {}
+        config.instance.changed.connect(self.config_changed)
+
+    def config_changed(self, attr: str) -> None:
+        if attr in self.cache:
+            self.cache[attr] = config.instance.get(attr)
+
+    def __getattr__(self, attr: str):
+        if attr not in self.cache:
+            assert not config.instance.get_opt(attr).supports_pattern
+            self.cache[attr] = config.instance.get(attr)
+        return self.cache[attr]

tests/unit/config/test_configcache.py

@@ -0,0 +1,35 @@
+# vim: ft=python fileencoding=utf-8 sts=4 sw=4 et:
+
+# Copyright 2018 Jay Kamat <jaygkamat@gmail.com>:
+#
+# 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/>.
+
+"""Tests for qutebrowser.misc.autoupdate."""
+
+import pytest
+
+from qutebrowser.config import configcache, config
+
+
+class TestConfigCache:
+
+    @pytest.fixture
+    def ccache(self, config_stub):
+        return configcache.ConfigCache()
+
+    def test_configcache_except_pattern(self, ccache):
+        with pytest.raises(AssertionError):
+            ccache['content.javascript.enabled']