Avoid error "All objects must exist on the server" on calling fetchAll()

[RaschidJFR]

Is your feature request related to a problem? Please describe.
When you need to fetch a list of objects which can be managed (or deleted) by other users, you risk getting an error "All objects must exist on the server" if any of those objects no longer exists.

Describe the solution you'd like
Ideally, the call to ParseObject.fetchAll() could ignore nonexistent objects and go on with the rest of the results.

Describe alternatives you've considered
The current way of avoiding this problem is not using fetchAll() but instead creating a new query:

let objectList = [...someObjects];
objectList = await new Parse.Query('Foo')
  .containedIn('objectId', objectList.map(o => o.id))
  .find();

[dplewis]

You could use fetchAllIfNeeded

[RaschidJFR]

Thanks. fetchAllIfNeeded() works... but:

• What about fetchAllWithInclude()? it still throws the error.
• Still, there's no way to tell that an object no longer exists on the server without try/catch. Maybe create something like ParseObject.exists()?

[dplewis]

await object.exists()or similar is a good idea. I've seen multiple developers ask for such a feature.

We could do FetchAllIfNeededWithInclude also.

@acinader @davimacedo What do you think?

[davimacedo]

I like both ideas.