How to get the exception Inner database is not open?

[CMCDragonkai]

I've noticed in my codebase when creating the sublevel, internally this error Inner database is not open gets thrown.

It's immediately applied to the cb inside the _open.

When using subleveldown, the call itself appears asynchronous.

So I have to use the open callback to know when the subleveldown is fully established.

However there doesn't seem to be a way to catch this exception of Inner database is not open.

I'm also not sure what is causing this exception.

[CMCDragonkai]

I found a way to do this:

      return await new Promise<DBLevel>((resolve, reject) => {
        const dbLevelNew = subleveldown(dbLevel, domain, {
          keyEncoding: 'binary',
          valueEncoding: 'binary',
          open: (cb) => {
            // This `cb` is defaulted (hardcoded) to a function that emits an error event
            // When using `level`, we are able to provide a callback that overrides this `cb`
            // However `subleveldown` does not provide a callback parameter
            // It provides this `open` option, which requires us to call `cb` to finish
            // If we provide an exception as a parameter, it will be received by the `error` event handler
            cb(undefined);
            resolve(dbLevelNew);
          },
        });
        // @ts-ignore error event for subleveldown
        dbLevelNew.on('error', (e) => {
          // Errors during construction of the sublevel will be emitted as events
          reject(e);
        });
      });

It would preferable that subleveldown matches the API of level, and level provides the ability to just pass the callback.

Atm even the types think that error is not a legitimate event. But it is indeed emitted.

Now I can actually handle the error properly:

(node:4099911) UnhandledPromiseRejectionWarning: OpenError: Inner database is not open
    at /home/cmcdragonkai/Projects/js-db/node_modules/subleveldown/node_modules/levelup/lib/levelup.js:119:23
    at /home/cmcdragonkai/Projects/js-db/node_modules/deferred-leveldown/node_modules/abstract-leveldown/abstract-leveldown.js:38:14
    at /home/cmcdragonkai/Projects/js-db/node_modules/deferred-leveldown/deferred-leveldown.js:31:21
    at /home/cmcdragonkai/Projects/js-db/node_modules/encoding-down/node_modules/abstract-leveldown/abstract-leveldown.js:38:14
    at /home/cmcdragonkai/Projects/js-db/node_modules/subleveldown/node_modules/abstract-leveldown/abstract-leveldown.js:38:14
    at onopen (/home/cmcdragonkai/Projects/js-db/node_modules/subleveldown/leveldown.js:142:50)
    at processTicksAndRejections (internal/process/task_queues.js:77:11)

[vweevers]

It would preferable that subleveldown matches the API of level

On that point: https://github.com/Level/abstract-level