Print Command Without Hitting Enter

Question

Suppose I map a key to enter a command in the command buffer, but without hitting enter:

function! BuildSystemTask()
    if inProject() "generic function that checks if I am in a buildable project
        :!make<Space>
    else
        echom("you are not in a valid project, whatever that means")
    endif
endfunction
nnoremap <Leader>b :BuildSystemTask()<CR>

The idea here is that I want to hit my mapping, and I would get "make " in the command buffer so that I can type whatever I want. However, this does not do it because it actually enters the whole command :!make<Space> as is in the command buffer.

I also tried :execute "normal! :make<Space>" and that didn't work either. It hits <CR> at the end.

Any idea how to do this? Or if if there is a better way to invoke a build command (make is here as an example. It could be node or go or maven). Or if there is a better way to achieve being able to pass arbitrary build command that would be helpful too.

Answer 1

I’d recommend an <expr> mapping—make the following changes:

nnoremap <expr> <Leader>b BuildSystemTask()

And then in your function:

if inProject()
  return ':make! '
else
  return ''

An alternative would be to use the feedkeys() function