How can I leave completion mode keeping the completion result in a binding when there's no popup?

Question

Currently:

• I have some key binding A → ^X^O (in insert mode) to omni-complete something
• I have some key binding B → ^Ogj to temporarily do something in normal mode (in this case, move down a display line)

However, if I press ^A^B, the second ^O conflicts with the first ^O and removes the omnicompletion.

How can I modify ^A so that it exits the ^X mode?

For normal typing I'd just use <esc>gj but this is in a binding.

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I did read help for i_CTRL-X and ins-completion, but I can't find any dedicated key. popupmenu-keys (^Y) only work when there's a popupmenu, in this case there isn't because there's only one completion entry.

I did find some workaround (posted as an answer below), but I may have missed some dedicated method to do it. (like ^Y in completion mode with popup)

_{For context, I'm typing </^X^O to omni-complete HTML tags.}

Answer 1

The second ^O actually functions like ^N when omnicompletion is active. From :h i^x^o, we see that

CTRL-O or CTRL-N : Use the next match. This match replaces the previous one.

To exit omnicompletion, we need a key that "does nothing", as suggested by your answer. One such combination is ^gU (This actually prevents a break in the undo sequence when used with <left>,<right>).

Thus the following mappings will work:

inoremap ^A ^X^O^GU
inoremap ^B ^Ogj

(where ^X is entered by pressing CTRL-VCTRL-X)

Answer 2

These are some workaround:

• <space><backspace>. Works (space is guaranteed to exit the completion mode), but doesn't seem very nice.
• <left><right>. Should work, as long as the expansion does not expand to nothing.
• <c-g><c-g>. This is no-op by now, but I think the behavior is not documented.
  • The above, and map <c-g><c-g> to <nop>. Does not work.
• <c-\><c-o>i.