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Our project is Xamarin Universal Windows Platform (UWP)
Running Realm 4.3.0 (from NuGet package)
If a migration is required, it seems realm config will either run the migration callback or a compact on launch, but we are getting an error when we try both in the same config.

We are only running Realm instances in the clients, not syncing to a server (yet). Our Xamarin project is running UWP, Android and iOS versions. UWP is the only one showing this issue.

Goals

We need to be able to run both a migration and a compact if a migration is required.
<!--- What are you trying to achieve? -->

Expected Results

We expect to run both without exception, both compacting the db if needed and running the migration callback when migration is needed.
<!--- What did you expect to happen? -->

Actual Results

Getting the following error:

System.InvalidCastException: Unable to cast object of type 'EventLoop' to type 'ShouldCompactDelegate'.
	at Realms.RealmConfiguration.ShouldCompactOnLaunchCallback(IntPtr delegatePtr, UInt64 totalSize, UInt64 dataSize)
	at Realms.SharedRealmHandle.NativeMethods.open(Configuration configuration, SchemaObject[] objects, Int32 objects_length, SchemaProperty[] properties, Byte[] encryptionKey, NativeException& ex)
	at Realms.SharedRealmHandle.Open(Configuration configuration, RealmSchema schema, Byte[] encryptionKey)
	at Realms.RealmConfiguration.CreateRealm(RealmSchema schema)at ERPXamarin.Models.AppModel.CompactRealm()

<!--- What happened instead? -->
<!--- e.g. the stack trace of a crash -->

Steps to Reproduce

The code sample below will catch an error if a migration is required.

I'm testing the migration by removing our application from the client, reverting back to an earlier version of our project which had Realm 4.2.0, running and installing, then upgrading to the latest version of our project which has Realm 4.3.0. The SchemaVersion is increased by 12.

If I remove ShouldCompactOnLaunch then MigrationCallback is called and the migration is successful. If I remove MigrationCallback, then ShouldCompactOnLaunch is called and does not result in an error. If both are included (if a migration is required) then ShouldCompactOnLaunch callback is run and then the error pops after that and MigrationCallback is never called.

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Code Sample

var config = new RealmConfiguration(RealmConfiguration.DefaultRealmName)
{
	SchemaVersion = 20,
	MigrationCallback = (Migration migration, ulong oldVersion) =>
	{
		//Do stuff here
	},
	ShouldCompactOnLaunch = (ulong totalBytes, ulong bytesUsed) =>
	{
		return bytesUsed/totalBytes < 0.9;
	}
};

try
{
	var realm = Realm.GetInstance(config);
	realm.Dispose();
}
catch (Exception e)
{
	//Error here: System.InvalidCastException
}

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Version of Realm and Tooling

• Realm Object Server Version:
• Flavor:
  • [ ] Realm Cloud
  • [x] Self-Hosted
• Server OS & Version: Only using Realm locally
• Client SDK Version: 4.3.0
• Client OS & Version: Windows 10, version 1903