config: Create read-only config proxy

mopidy/__main__.py

@@ -74,17 +74,20 @@ def main():
         log_extension_info(installed_extensions, enabled_extensions)
         check_config_errors(config_errors)
 
-        log.setup_log_levels(config)
+        # Read-only config from here one please.
+        proxied_config = config_lib.Proxy(config)
+
+        log.setup_log_levels(proxied_config)
         create_file_structures()
         check_old_locations()
         ext.register_gstreamer_elements(enabled_extensions)
 
         # Anything that wants to exit after this point must use
         # mopidy.utils.process.exit_process as actors have been started.
-        audio = setup_audio(config)
-        backends = setup_backends(config, enabled_extensions, audio)
+        audio = setup_audio(proxied_config)
+        backends = setup_backends(proxied_config, enabled_extensions, audio)
         core = setup_core(audio, backends)
-        setup_frontends(config, enabled_extensions, core)
+        setup_frontends(proxied_config, enabled_extensions, core)
         loop.run()
     except KeyboardInterrupt:
         if logging_initialized:

mopidy/config/__init__.py

@@ -144,3 +144,23 @@ def parse_override(override):
     section, remainder = override.split('/', 1)
     key, value = remainder.split('=', 1)
     return (section.strip(), key.strip(), value.strip())
+
+
+class Proxy(collections.Mapping):
+    def __init__(self, data):
+        self._data = data
+
+    def __getitem__(self, key):
+        item = self._data.__getitem__(key)
+        if isinstance(item, dict):
+            return Proxy(item)
+        return item
+
+    def __iter__(self):
+        return self._data.__iter__()
+
+    def __len__(self):
+        return self._data.__len__()
+
+    def __repr__(self):
+        return b'Proxy(%r)' % self._data