How to combine views exposed filter with search? My client asked me for a single field, that would work 2 ways:


Autocomplete filter based on taxonomy.
If site visitor inputs something that's not in taxonomy, full text search should be performed on content's body, and appropriate info message shown.


That way if user enters category name, he will get hand picked nodes listed, and if anything else, he will at least get some content.

Separately, it's easy. But how to combine these behaviours in one field?
Finder module will do your requirement exactly, You can select taxonomy term as well as node title, body, fields, ..etc to perform the search. 


  There are many ways to put together finder's functionality to get the
  sort of search form you need. There are also many hooks and theme
  functions allowing full customization of finder's output.


It is used for these purposes:

As a search tool to find a group of nodes or users.
As a way to navigate to a specific node or user page that matches criteria.
As an alternative to exposed filters for a Views module display.


See the below screen shot, In the finder field you can choose taxonomy terms as well as node body to perform the search in auto-complete exposed field, even you can perform multiple keyword search separated by comma. Read the Finder documentation for more information..



Once you added the element you can select the finder fields from the list, hold the 

Ctrl key to select the taxonomy term as well as Node: Body