We try to very hard to avoid changes that might break 3rd party custom features but every now and then we can't avoid it if we want to move forward.
Some major improvements to the site search index were just completed and this resulted in a breaking change for anyone who has implemented search in their custom features building on top of our internal lucene.net search index.
Fixing your broken code is straightforward. Get the latest mojoPortal code and then compile your feature against it. Anywhere that it breaks (doesn't build) on search index related code just add:
Other than that, in your indexbuilder you should assign new properties on IndexItem for CreatedUtc and LastModUtc to reflect those properties on your content. Also if your feature has a separate field for an excerpt, abstract, or summary, you should assign that on indexItem.ContentAbstract. There is also a new property for indexItem.Author that you can populate if it makes sense for your feature to show that in search results.
Sorry for the inconvenience but I think it will be worth it having these search index improvements for the long term.