Storage Design

StateStorageBackedByController

StateStorageBackedByController is a special implementation of StateStorage. It's another PSC bridge implementation and currently, it's only used for cache (StoragePathMacros.CACHE_FILE).

You might wonder why it's not used for internal settings.

• It lacks numerous features like support for StreamProvider (settings sync, settings import). While we could potentially overcome this, the return on investment isn't evident for now.

• Regarding backward compatibility — would it be appropriate to transfer internal settings from the old storage to a new one upon opening the new IDE version?

So, how does it work? It utilizes the same unified format and also employs JsonElementSettingSerializerDescriptor as the setting key serializator. Although the implementation shares some similarities with the PSC bridge, it's not completely identical. As StateStorageBackedByController is an exclusive storage, we don't need to handle local data (e.g., merging).

Currently, LocalSettingsController only supports keys with CacheTag and NonShareableInternalTag tags. It uses MVStore to store data on the disk. Specifically, we use MVMap<String, ByteArray> — where the setting key is transformed into a string (plugin id + setting key). Any type of value is serialized into CBOR. This allows us to deserialize the value later without knowing the data type - whether it's a string, number, etc. As of now, this feature is utilized by DumpDevIdeaCacheDb to dump the MVStore database into YAML.

For JsonElementSettingSerializerDescriptor, where the serializer cannot be used for any format beyond JSON, we encode the JSON element into a string, and subsequently encode it to CBOR. So, the value gets stored as a CBOR string.