Within a function, Is there a way to determine if vim is in insert mode?

Question

Within a function, is there a way to determine if vim is in insert mode (or was in insert mode prior to calling the function)?

Answer 1

Something must have invoked your function. Setting the (new in Vim 8.0) asyncronous timers aside, this will be either

• a custom command, which cannot be invoked from insert mode, only command-line mode
• a mapping
• an :autocmd event

For the latter, you can split into two separate :autocmds, and pass an isInsertMode flag into your function:

autocmd CursorHold,CursorHoldI * call MyFunc()

turns into

autocmd CursorHold  * call MyFunc(0)
autocmd CursorHoldI * call MyFunc(1)

For mappings, you can pass a similar flag, or a character representing the mode (to also handle visual mode and so on):

:nnoremap <F2> :call MyFunc('n')<CR>
:vnoremap <F2> :<C-u>call MyFunc('v')<CR>
:inoremap <F2> <C-o>:call MyFunc('i')<CR>

That is the canonical approach, and should work for most use cases. If you have a really special need, please elaborate in your question.

Answer 2

There is mode() function which can be used in some contexts (not thoroughly documented) with the following description:

mode([expr])    Return a string that indicates the current mode.
...
                  i       Insert

So, when it works, check for insert mode in your function can look like this:

if mode() == 'i'
    " in insert mode
endif

Answer 3

Jist of hinging behavior on the mode that you are in:

The reason that determining what mode you're in is difficult is because you're trying to decide something in a place where that information is generally not kept.

So move upstream and put your hinge on mode in the nnoremap, inoremap, vnoremap, etc, like this:

nnoremap jj :call DecoupleDilithiumMatrix()
nnoremap jk :call EjectWarpCore()

Then you can put your mode-specific code in the functions.