A cyclic dependency between available-for-plugins.js and get-data-fetcher.js

[sehilyi]

I am trying to figure out a way to refactor the higlass code in order to publish smaller packages (e.g., @higlass/core, @higlass/data-fetchers, etc) which will be helpful for other projects that use only a subset of higlass. But I found many cyclic events happening, especially on available-for-plugins.js, which makes it challenging to separate packages.

One example I found is that a getDataFetcher function (from get-data-fetcher.js) uses an AVAILABLE_FOR_PLUGINS object (from available-for-plugins), but AVAILABLE_FOR_PLUGINS itself also stores the getDataFetcher function.

  - configs
    - available-for-plugins.js
  - data-fetchers
    - get-data-fetchers.js

// configs/available-for-plugins.js
import getDataFetcher from '../data-fetchers/get-data-fetcher';
const dataFetchers = {
  getDataFetcher, ...
};
export default {
  dataFetchers, ...
}

// configs/index.js
export { default as AVAILABLE_FOR_PLUGINS } from './available-for-plugins';

// get-data-fetcher.js
import { AVAILABLE_FOR_PLUGINS } from '../configs';
const getDataFetcher = (
   ...,
   availableForPlugins = AVAILABLE_FOR_PLUGINS
) ⇒ {
   ...
};

export default getDataFetcher;

I am unsure if AVAILABLE_FOR_PLUGINS.getDataFetcher() is used at all from plugin tracks or data fetchers, but it is at least not used in the higlass/higlass repo. Several plugin repos under higlass (e.g., higlass/higlass-sequence) do not use it, too. I think we could remove getDataFetcher from AVAILABLE_FOR_PLUGINS if we are certain it is not used, or we will need to restructure them.

cc @manzt

[sehilyi]

Actually, AVAILABLE_FOR_PLUGINS.getDataFetcher() is used in a data fetcher implemented outside the higlass repo:

https://github.com/kundajelab/higlass-multi-tileset/blob/a6d89b4afbd9749d68b2f30b397dd0a07da63b6d/src/scripts/multi-tileset-fetcher.js#LL10C75-L10C89