Change record status: 
Project: 
Introduced in branch: 
11.3.x
Introduced in version: 
11.3.0
Description: 

Views plugins were able to specify a theme_file key in their plugin annotation to indicate an include file that contained their preprocess functions.

Since template preprocess callbacks are now explicitly registered in the hook_theme definition and views theme hooks defined for plugins support a standard preprocess callback, this key is deprecated.

The theme_file key is already not available in plugin attributes and support for it is removed in Drupal 12.0. As a minimal conversion, the functions can be moved to the .module file, or converted to the recommended OOP format.

Impacts: 
Module developers