InMemoryRealm-Bug

Issue can be tracked here: realm/realm-swift#7017

NOTE: This only happens using InMemoryRealm configuration something like Realm.Configuration(inMemoryIdentifier: "messagesRealm")

Goals

I am writing a cache protocol which I can implement later using any or multiple cache libraries (regardless of disk or memory), in this case it is Realm

Expected Results

Expectation was when the save function is called realm should successfully save the object in memory and when retrieved it should return it successfully or return all objects.

Actual Results

In memory realm is returning empty every time I insert something and try to fetch it (I am 100% sure it is inserting successfully and I will explain later why)

Steps for others to Reproduce

Reproduce the problem

Clone the git repository in Code Sample
Compile and run on a simulator/device (they both are giving the same results)
In the Message field write anything
Press Save
Now press Refresh it should populate a list with data but it won't do it

What I have done

While reproducing the problem navigate to Realm -> InMemoryRealmCache.swift and setup a breakpoint at line 94.
Now run the application again and repeat step 3 to 4 the application should break after pressing Save
In the lldb write po realm.objects(MessageRealmEntity.self) and finally continue the application
Now press Refresh and the list will be populated No matter how many times you add and refresh it will work now 100%.

Video to show the problem and how to reproduce

realm-bug_nlFwK7Nu.mov

Code Sample

This is a git repository for a dummy application to reproduce the bug:

https://github.com/Muhand/InMemoryRealm-Bug

Version of Realm and Tooling

Realm framework version: RealmSwift (10.1.4)

Realm Object Server version: ?

Xcode version: Version 12.2 (12B45b)

iOS/OSX version: iOS 14.2

Dependency manager + version: ?

Few important notes

As can be seen in the project I am initializing Realm in every function in my wrapper this way I can avoid Realm accessed from incorrect thread issue.
However, to avoid realm being initialized on different threads I made sure to set a DispatchQueue in which they all are initialized and ran in.
I have tried making my Realm object to be static and living somewhere else but this is not scalable and if someone in the team called the functions from a different thread it can crash the app with the error Realm accessed from incorrect thread
The wrapper works 100% fine if I am using disk realm instead of memory
The wrapper is initialized only once so I don't have multiple instances of it