completion-annotate-function

completion-annotate-function is a variable defined in `minibuffer.el'.
Its value is

nil

• This variable is obsolete since 24.1;
  use `completion-extra-properties' instead.
• This variable may be risky if used as a file-local variable.

Documentation:
Function to add annotations in the *Completions* buffer.
The function takes a completion and should either return nil, or a string that
will be displayed next to the completion. The function can access the
completion table and predicates via `minibuffer-completion-table' and related
variables.