You only need to do steps 2.1-2.4 if you've used grids which didn't have the default value for MaxCellsPerGroup (-1).

Ideally, you'd read this before importing the package.
If you already imported it, undo the changes so you can start fresh - with a working v4.2 version, i.e. this migration is done before importing the new version.

1. Backup
2.1 [Optional if you've used grids which didn't have the default value for MaxCellsPerGroup (-1)]
2.2 Add this code to any class (let's say GridParams, for example):
<code>
[UnityEditor.MenuItem("Tools/OSA/Migrate all _MaxCellsPerGroup in scene")]
static void MigrateMaxCellsPerGroup()
{
	var objs = Resources.FindObjectsOfTypeAll(typeof(UnityEngine.GameObject));
	string migrationResult = "Migrated: ";
	foreach (var ob in objs)
	{
		var go = ob as GameObject;
		var osa = go.GetComponent(typeof(IOSA)) as IOSA;
		if (osa == null)
			continue;

		var p = osa.BaseParameters as GridParams;
		if (p == null)
			continue;

		if (p.grid == null)
			p.grid = new GridConfig();
		p.grid.MaxCellsPerGroup = p._MaxCellsPerGroup;

		migrationResult += go.name + ", ";
	}
	Debug.Log(migrationResult);
}
</code>
2.3 execute the newly created menu item in each of your scene (if you're using prefabs, you need to have them included in the scene so they can be affected, and then 'Apply' the changes)
2.4 remove the above
3. Delete old folder "Assets/OSA" (You need this because importing unitypackages doesn't remove files that are not needed anymore)
4. Import new package
5. If you previously imported the Utils, Demos or any other sub-package, re-import it now.
6. Fix all compile errors. Most common issues:
    * New `AbstractViewsHolder.Init` method. Example:
        - instance.Init(_Params.itemPrefab, itemIndex);
        + instance.Init(_Params.itemPrefab, _Params.Content, itemIndex);
    * `_VisibleItems` is intern now, use `GetItemViewsHolder(index)` and `VisibleItemsCount` to iterate over them
7. In version 4.2.1 and up, the prefab's size dictates the DefaultItemSize property in BaseParamsWithPrefab, but if you use a prefab that's not in the scene, it'll report an invalid size. 
	The simple solution is to bring the prefab in the scene. 
	The other solution is to replace the BaseParamsWithPrefab with the one provided on our <a href="https://discord.gg/qjwjBYy">discord server</a> in the <a href="https://discordapp.com/channels/562559159254384641/578593785249005578/647797593241419828">#announcements-verified-osa-users</a> channel (you need the Verified role - more info there) .
	Or wait for v5.0.1 (not released as of the current date, 23 Nov 2019)