Globally converts all (impossible, deleted) values of a specific enum to (new, correct / updated) values

GlobalUnityEnumUpdater.cs

public class UpdateableMyStruct
{
	public Func<MyStruct> getter;
	public Action setter;
	public string attribute;
	public string ownerName;
}

public class ProposedChanges
{
	public List<UpdateableMyStruct> toChange;
}

///
/// You made a mistake in your unity asset / game / whatever: you had an enum
/// with values eg "1, 2, 3, 4", and now you only have values "0, 1, 2"; you
/// need to convert all instances of "3" to (e.g.) "0".
///
/// Add this class to an empty Game object, then right-click the component to
/// get the popup menus to check what it will change, and to run the changes.
///
/// I used this to fix 10,000's of wrong/legacy enum values - executes instantly
/// even on moderately large scenes.
///
/// Use this code at your own risk - commit your project to git/repo first, and
/// check it's updated the right things correctly before continuing development
///
public class GlobalUnityEnumUpdater : MonoBehaviour
{
	private ProposedChanges _CalculateProposedChanges()
  {
		var items = Resources.FindObjectsOfTypeAll<MyComponent>().ToList();

		var proposedChanges1 = new List<UpdateableMyStruct>();
		items.ForEach( item =>
		{
			proposedChanges1.AddRange( StructsThatNeedUpdating( item ) );
		} );

		return new ProposedChanges()
		{
			toChange = proposedChanges1,
		};
	}

[ContextMenu( "find all enums that need updating" )]
	public void Menu_FindAll()
	{
		var proposal = _CalculateProposedChanges();
		Debug.Log( "...found "+(proposal.toChange.Count)+" attributes that need changing" );
		
		OutputChanges( proposal.toChange );
	}
	
	[ContextMenu( "UPDATE all enums that need updating" )]
	public void Menu_UpdateAll()
	{
		var proposal = _CalculateProposedChanges();
		
		PerformChanges( proposal.toChange );
	}
  
  private List<UpdateableMyStruct> StructsThatNeedUpdating( MyComponent owner )
	{
		var r = new List<UpdateableMyStruct>();
		
    int illegalOldValueOfStruct = 3;
		if( (int)owner.structFieldName.enumName == illegalOldValueOfStruct )
			r.Add( new UpdateableMyStruct() {getter = () => owner.structFieldName, setter = oldValue => owner.SetWithoutNotify_structFieldName( new MyStruct( [acceptable new values] )), attribute = ".structFieldName", ownerName = owner.name } ); 
      
		return r;
	}
  
  private void PerformChanges( List<UpdateableMyStruct> uls )
	{
		foreach( var ul in uls )
			ul.setter( ul.getter().value );
	}
  
  private void OutputChanges( List<UpdateableMyStruct> uls )
	{
		foreach( var ul in uls )
			Debug.Log( "Will change: "+ul.getter()+" on object: "+ul.ownerName );
	}
  }