call omnicompletion from vimscript

Question

I'd like to automatically call the omnicompletion (that is triggered manually by <Ctrl-X><Ctrl-O>) from within a vimscript function.

I played around a bit with execute 'normal! …' and feedkeys(), but if I got it do actually do something, it always results in a literal \<C-X>\<C-O> in my document.

How can I call the omnicompletion from within a vimscript function?

Edit:

What I have tried so far (to simplify the example, I just jump to line 27, enter a new line below it and start omni-completion):

execute 'normal! 27Go\<c-x>\<c-o>'

  execute 'normal! 27Go'
  startinsert
  execute 'normal! \<c-x>\<c-o>'

  execute 'normal! 27Go'
  startinsert
  call feedkeys('\<c-x>\<c-o>')

Edit 2:

Hah, thanks to @ChristianBrabant I played around a bit more and found that feedkeys() should work, but I just used it wrongly! See my own answer below: https://vi.stackexchange.com/a/21713/21417

Answer 1

feedkeys() is the correct approach, but to respect the special keys, I must use double quotes (as mentioned in the vimhelp):

  execute 'normal! 27Go'
  startinsert
  call feedkeys("\<c-x>\<c-o>")