RCOCOA-2271: Collections in Mixed

[dianaafanador3]

• Added support for storing nested collections (List and Map not ManagedSet) in a AnyRealmValue.

  class MixedObject: Object {
    @Persisted var anyValue: AnyRealmValue
  }
  
  // You can build a AnyRealmValue from a Swift's Dictionary.
  let dictionary: Dictionary<String, AnyRealmValue> = ["key1": .string("hello"), "key2": .bool(false)]
  
  // You can build a AnyRealmValue from a Swift's Map
  // and nest a collection within another collection.
  let list: Array<AnyRealmValue> = [.int(12), .double(14.17), AnyRealmValue.fromDictionary(dictionary)]
  
  let realm = realmWithTestPath()
  try realm.write {
    let obj = MixedObject()
    obj.anyValue = AnyRealmValue.fromArray(list)
    realm.add(o)
  }

• Added new operators to Swift's Query API for supporting querying nested collections.

  realm.objects(MixedObject.self).where { $0.anyValue[0][0][1] == .double(76.54) }

  The .all operator allows looking up in all keys or indexes.

  realm.objects(MixedObject.self).where { $0.anyValue["key"].all == .bool(false) }

[dianaafanador3]

This is waiting for this PR to be merged to core. Also, there is one failing test which is working locally, taking a look at it, but putting this on review on the meantime.

[tgoyne]

A first pass over things.

[tgoyne]

Similarly, this is not at all a valid Hashable implementation.

[dianaafanador3]

Using ObjectIdentifier given that we already conform to Equatable

[tgoyne]

ObjectIdentifier is not a valid definition either. Two managed dictionary objects which correspond to the same field are equal to each other but have different ObjectIdentifiers. All of our accessor types are fundamentally incompatible with Hashable due to that their identity changes when you promote an unmanaged object.

[dianaafanador3]

@tgoyne we do need to conform to Hashable to be able to include Map or List as a an associated value in AnyRealmValue if we want to go that approach.
I can think of a few approaches for this:

• Use ObjectIdentifer and sacrifice equality for managed and unmanaged object
• Have associated values as Swift's native types Array/Dictionary, this will clearly will go bad with nested collections which will need to be instantiated completely to convert it (Discarded)
• Store some reference to the collection as the associated value and then and have some static function that returns the collection (Not need to conform to hashable, but worse developer experience).

I'm open to discuss different solutions

[tgoyne]

We can override the hash function on AnyRealmValue and return a constant value for the Map and List cases.

[leemaguire]

why would currentProperty be nil here?

[dianaafanador3]

For any other mixed wrapped types besides list and dictionary the accessor is constructed without the current property because it is not needed to box the native value

[tgoyne]

There are still several new warnings. I'm not sure why the implicit casts from id to RLMArray are producing warnings here but not on master, but the other warnings seem straightforward.

[tgoyne]

If you do $0.anyCol["'"] == 0 to query on the dictionary key "'" this will produce invalid syntax.

[dianaafanador3]

@tgoyne solved PR comments and removed the warnings

[tgoyne]

Returning RLMPropertyTypeAny seems like the best option here.

REALM_UNREACHABLE() marks a place that should be logically impossible to hit and if we get there it always indicates a bug in our code.

[tgoyne]

I don't know what you mean. any["'"] == %@ (or any['\''] == %@) is a perfectly valid query, which this currently fails to generate a valid string for.

[tgoyne]

These should all be hasher.combine(i) without the .hashValue. This currently is hashing the values and then rehashing the hash.