Show path of file from where the code autocompletion is coming from

Question

When doing auto completion with CTRL+n, I see autocompletion suggestions from the current file as well as from different other files all mixed together as seen below:

I would like to get a behavior similar to what is shown on the below picture, i.e. display the path of the file containing the suggestion if the suggestion is coming from file other than the current one.

Answer 1

Normally it work if you have your file opened as buffer in vim. The autocompletion will look at them when you launch CTRL_P or CTRL_N (see :help complete):

'complete' 'cpt'        string  (default: ".,w,b,u,t,i")
                        local to buffer
        This option specifies how keyword completion ins-completion works
        when CTRL-P or CTRL-N are used.  It is also used for whole-line
        completion i_CTRL-X_CTRL-L.  It indicates the type of completion
        and the places to scan.  It is a comma separated list of flags:
        .       scan the current buffer ('wrapscan' is ignored)
        w       scan buffers from other windows
        b       scan other loaded buffers that are in the buffer list
        u       scan the unloaded buffers that are in the buffer list 
        U       scan the buffers that are not in the buffer list
        k       scan the files given with the 'dictionary' option
        kspell  use the currently active spell checking spell
        k{dict} scan the file {dict}.  Several "k" flags can be given,
                patterns are valid too.  For example:
                        :set cpt=k/usr/dict/*,k~/spanish
        s       scan the files given with the 'thesaurus' option
        s{tsr}  scan the file {tsr}.  Several "s" flags can be given, patterns
                are valid too.
        i       scan current and included files
        d       scan current and included files for defined name or macro
                i_CTRL-X_CTRL-D
        ]       tag completion
        t       same as "]"

Answer 2

Assuming you are using the built-in :help ins-completion, I can only think of two reasons why the name of the buffer where the suggestion comes from is not displayed:

• The buffer is unnamed.
• The keyword is also present in the current buffer.

In the screenshot below, taken in $ vim -Nu NONE, foo doesn't get a bufname because it is already in the current buffer, football and foobar both get a bufname because they are from buffer foo (naming is hard), and icare doesn't get a bufname because it is from an unnamed buffer.