How to add Firestore emulator support?

Right now when trying to connect to locally hosted Firestore emulator from Unity a mysterious exception is thrown:

Firebase.Firestore.FirestoreException : 
false for 'get' @ L6
---
at Firebase.Firestore.Internal.Util.FlattenAndThrowException (System.Threading.Tasks.Task completedTask) [0x00016] in Z:\tmp\tmp.DnKB31Zq3X\firebase\firestore\client\unity\proxy\Util.cs:94 
  at Firebase.Firestore.Internal.Util+<MapResult>c__AnonStorey0`2[T,U].<>m__0 (System.Threading.Tasks.Task`1[TResult] completedTask) [0x00000] in Z:\tmp\tmp.DnKB31Zq3X\firebase\firestore\client\unity\proxy\Util.cs:59 

After debugging SDK C# code I found out that error code of 7 (PermissionDenied) is also present.

I use these settings:

Settings.Host = "localhost:8080";
Settings.SslEnabled = false;
Settings.PersistenceEnabled = false;

I desperately need to support Firestore emulator in Unity. I will try to build SDK from source and implement emulator support myself.

How hard will it be? Does CPP SDK support emulator? Is it known where the problem lies?

I looked inside Android/Java Firebase SDK and it does not seem to be doing anything special besides setting port, host, ssl and persistence.

[dconeybe]

I’ve logged b/202835732 (for Googlers) to see what we can do to improve the error message produced when a Firestore operation is rejected by security rules.

[dconeybe]

A quick Google search brought me to this post: https://stackoverflow.com/a/62171642/12975006

Could you ensure that your security rules in the emulator are sufficiently permissive to allow the writes?