I'm not really sure how to describe this behavior better than with the example I'm dealing with.

I'm trying to write a custom completion using fzf-vim ... and as I'm looking through the documentation, there is a section that describes how to do it briefly, but since I don't understand it fully, I wanted to play with the API.

So naturally I thought I'd be able to just do

:call fzf#vim#complete('cat /usr/share/dict/words')

instead of binding it to a binding and using that binding like they show with

inoremap <expr> <c-x><c-k> fzf#vim#complete('cat /usr/share/dict/words')

but the problem is, while the binding does pop up fzf, the :call fzf#vim#complete(...) seems to do nothing.

I'm not sure what is causing this behavior, and if there is some other way I should be invoking the function? I don't mind reading stuff up in the documentation and learning about vimscript, but at this point I really don't know where to look anymore

As a side note, what I'm actually trying to do is create a fzf wrapper around :digraph. I wasn't sure if this would be possible with just the output of :digraph, so I found unicode.vim which even provides a function FindUnicodeBy which seems I should be able to just pass into the fzf#vim#complete wrapper, but I can't even figure out how to test the completion function.

Any tips are very welcome, as well as references to stuff to read to be able to work better with vimscript!

  • For reading references, the help, vimruntime, and Steve Losh’s « Learn vimscript the hard way » are good starts.
    – D. Ben Knoble
    Dec 11, 2018 at 18:09
  • 3
    Jacub, try :echo fzf#vim#complete('cat /usr/share/dict/words'). See :help :map-expression.
    – Ralf
    Dec 11, 2018 at 19:18

1 Answer 1


This touches the implementation details of fzf#complete. If you look into the source code of fzf#vim#complete, you will see

call feedkeys("\<Plug>(-fzf-complete-trigger)")
return ''

So when you do imap <expr> xxxx fzf#vim#complete(), what returns from the expression is '', and the key \<Plug>(-fzf-complete-trigger) stored in a buffer and is to be processed later. This key is actually defined by

imap <Plug>(-fzf-complete-trigger) <c-o>:call s:_complete_trigger()<cr>

There is no nmap defined for it. So you won't get anything if you do

:call fzf#vim#complete('cat /usr/share/dict/words')

I actually didn't get your purpose to run it in normal mode. But if just want to have this ability, you can do

nmap <expr> xxx 'i' . fzf#vim#complete('cat /usr/share/dict/words')

or (this method adds key i before \<Plug>(-fzf-complete-trigger)

:call feedkeys("i") | call fzf#vim#complete('cat /usr/share/dict/words')

or to modify fzf source code to expose s:_complete_trigger as a global function and call that function.

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