Easy way to declare custom Cache

Summary

It would be nice if I could declare a cache class in CacheSettings. Currently you have to patch multiple things, including Bot._cache and Bot._event_manager._cache.

Why is this needed?

To add to or modify the default cache.

Ideal implementation

An extra setting in CacheSettings for cache class; it should expect a subclass of CacheImpl. Then it can set self._cache = cache_settings.cache_class(...), or something of the sort.

Checklist

• I have searched the issue tracker and have made sure it’s not a duplicate. If it is a follow up of another issue, I have specified it.

[ahnaf-zamil]

Yeah that’s what I said in the last part of my reply. The GatewayBot could take in a cache impl as a constructor arg, and then use that. But at the moment, it’s hardcoded to use hikari’s default CacheImpl, and the only way to change it is to override _cache and _event_manager._cache.

[FasterSpeeding]

For example, the current cache only stores existing values. What if I wanted to store None for deleted messages, so that I don’t fetch non-existing messages repeatedly?

BTW this example would likely fall under #880 (although it’d never quite apply to messages since that cache store is always incomplete)