Search toolkit for Drupal 8
The current core Search module presents an API that tries to be generic, but ends up being insufficient for many advanced uses or for non-SQL back-ends.
the parts of the current Search module that are most useful are UI elements like the search page, form, and theme functions so that themes can look good for any module re-using those.
The current Search module suffers from a lack of maintainer-ship. We need to simplify the functionality provided by the core back-end so it becomes easier to maintain (and test) going forward.
In addition, new effort should focus on providing in Core a Search Toolkit that provides a framework and basic implementation for the UI, but moves away from any attempt to interface generically with the indexing process or other pieces that are back-end specific. A key portion of such a toolkit would be adapted from the Facet API module
In addition, we should remove the advanced search form from core, remove most of the complex query parsing from core, and provide implementations of a couple facets for core via the SQL back-end.
The net advantage is that new search UI elements could be used across back-ends, and theming would be more consistent regards of how the search results are generated.
