fix(plugins): discovery must not instantiate an imported base class

[warksit]

The bug

load_plugin()'s preferred detection strategy takes the first class whose name ends in Plugin:

for name, obj in inspect.getmembers(plugin_module, inspect.isclass):
    if name.endswith("Plugin"):
        plugin_instance = obj(self.base)
        break

inspect.getmembers() returns members alphabetically. Every plugin does from plugin_system import PredBatPlugin, so the abstract base class is in the module namespace and is itself a match. Any plugin whose class name sorts after PredBatPlugin therefore gets the base instantiated instead of itself.

When that happens the plugin looks completely healthy in the log:

Initialising plugin class (name-based): PredBatPlugin
Successfully loaded plugin: soc_keep_publish_plugin

…but PredBatPlugin.register_hooks() is a no-op, so no hooks are registered and the plugin silently does nothing. There is no error, no warning, and the entity it was supposed to publish simply goes stale.

Whether a plugin works depends on the luck of its class name. I hit this with a plugin class called SocKeepPublishPlugin; ColdWeatherPlugin and CurtailmentPlugin happen to sort before PredBatPlugin, which is the only reason they were unaffected.

The fix

Require the candidate class to be defined in the plugin file, not merely imported into it:

if name.endswith("Plugin") and obj.__module__ == plugin_module.__name__:

This also covers the general case of a plugin importing any other helper class ending in Plugin.

The two fallback strategies (the PREDBAT_PLUGIN marker and the initialize_plugin() function) are unchanged.

Compatibility

No API change and no behaviour change for any plugin that was already working — a plugin class defined in its own file still matches exactly as before. The only plugins affected are ones that were silently broken.

Testing

Added test_plugin_discovery_skips_imported_base_class to the existing tests/test_plugin_startup.py (no new files). It writes a temp plugin whose class name deliberately sorts after PredBatPlugin, runs real discovery over it, and asserts the correct class was instantiated.

Confirmed it fails without the fix:

ERROR: discovery instantiated PredBatPlugin, expected ZzSortsLastPlugin
**** ERROR: Test plugin_discovery FAILED

and passes with it. Registered in unit_test.py as plugin_discovery. Full unit_test.py --quick passes, pre-commit run clean.

🤖 Generated with Claude Code

https://claude.ai/code/session_01WY52NvNyVdznsF4VcVG8Q8