Add a get/set helpers to the function cache.function returns

[fregante]

const getDefault = cache.function('default', calculate);

await getDefault(); // Calls the function if not set

await getDefault.get(); // Only gets the cached value

await getDefault.set(await calculate()); // Only sets the value directly into the cache

// We already have this
await getDefault.fresh(); // Skips the cache if it exists, calls the function

Live examples:

• https://github.com/refined-github/refined-github/blob/60ac04e85cdb0c597e90d3d314ad6fb4c1fe4d8d/source/features/link-to-changelog-file.tsx#L27

[fregante]

It turns out, I hate this whole module API.

I'll update it to a class so that it's more type-safe:

const file = new CacheItem<string>('file');
await file.get();
await file.set('yolo');
await file.delete();

and I will integrate the getter/updater:

async function curl(url: string) {
  const r = await fetch(url);
  return r.text()
}
const contents = new CacheItem<string>('contents', curl);
await contents.get('https://example.com'); // checks cache, then makes calls curl(url: string)
await contents.getFresh('https://example.com'); // calls curl(url: string) only
await contents.getCached('https://example.com'); // checks cache for `url` only
await contents.set('https://example.com', 'contents'); // skips `curl`, sets cache directly, must match type
await contents.delete('https://example.com'); // delete cached item
await contents.clear(); // clears the entire 'contents' cache