Map key to interrupt Insert-mode completion

Question

Often, insert-mode completion can take some time (e.g. <C-x><C-l> on a common prefix in your project). <C-c> interrupts this. I'd like to map another key to also have this interrupt behaviour, like so:

inoremap <C-k> <C-c>

However, it seems that on <C-k>, the mapping only gets processed after the completion finishes, contrary to <C-c>.

How can I make my mapping also interrupt insert mode completion?

Edit:

To clarify, the problem is not about detecting whether we are in completion-mode. This can be achieved with pumvisible() or complete_info(). The problem is that before the popup menu appears, that is, when vim is (slowly) scanning a completion, the mappings don't trigger until scanning completes, unlike <C-c> (defeating the purpose of mapping something to <C-c>), which immediately interrupts the scanning without waiting for scanning to finish.

Answer 1

A simple insert mode mapping can't work because triggering completion puts you in a special "submode", note the quotes, where your mappings won't work and that doesn't have its own prefixed *[nore]map commands.

Moreover, :help i_ctrl-k is a very useful command that you should probably not override.

The solution can be found under :help ins-completion-menu:

There are no special mappings for when the popup menu is visible.  However,
you can use an Insert mode mapping that checks the pumvisible() function to
do something different.  Example:
    :inoremap <Down> <C-R>=pumvisible() ? "\<lt>C-N>" : "\<lt>Down>"<CR>

In your case:

inoremap <C-k> <C-R>=pumvisible() ? "\<lt>C-c>" : "\<lt>C-k>"<CR>

which:

• does <C-c> when you press <C-k> while the popup menu is visible,
• does <C-k> otherwise, so there is no loss in functionality.