ResolveItemTask.cs

    public class ResolveItemTask : IConfigurationResolverTask
    {
        public void Execute(ConfigurationResolverArgs args)
        {
            // Don't impact out of the box functionality for the page editor.
            if (Sitecore.Context.PageMode.IsPageEditorEditing)
                return;

            var context = (SitecoreTypeCreationContext)args.AbstractTypeCreationContext;

            // Item does not exist or language version already exists, bail out.
            if (context.Item == null || context.Item.Versions.Count > 0)
                return;

            var languageFallbackState = Switcher<LanguageItemFallbackState>.CurrentValue;
            if (languageFallbackState == null || languageFallbackState.Languages == null)
                return;

            var service = (SitecoreService)args.Service;
            var id = context.Item.ID;
            foreach (var language in languageFallbackState.Languages)
            {
                var item = service.Database.GetItem(id, language);

                // Bail out if no item.  In this case item should be null regardless of language. (you will always get a language version back regardless of translations)
                if (item == null)
                    break;

                // No language version exists.  Check the next language
                if (item.Versions.Count == 0)
                    continue;

                context.Item = item;
                break;
            }
        }
    }