<Tab> out of insert mode - lua keymap

Question

I'm a relatively new neovim user. I use nvim-autopairs to always induce matching (, [, {, ', " character pairs, and automatically placing my cursor inside them. As an example, in insert mode, if I type (, I get ($), where $ represents my active cursor insert mode position.

I want to have a keybinding in insert mode to allow me to <Tab> out of the ending pair, and remain in insert mode, ready to keep going. So I would like to type in insert mode, (x, y<Tab> to obtain (x, y) $, where again $ represents my cursor in insert mode ready to continue typing. Note the requirement of the extra space between ) and $ above.

I found this reddit thread which apparently does this keybinding, with a more advanced implementation in the same thread. I tried to implement the advanced implementation as follows in my init.lua file:

-- tab out of `(['` etc in insert mode
vim.keymap.set('i', '<Tab>', getline('.')[col('.')-1] =~? '[]>)}]' || getline('.')[col('.')-1] =~? '[''"`]' && synIDattr(synID(line("."), col(".")+1, 1), "name") !~? 'string', {silent = true, expr = true, remap =false})

But I get a syntax error when restarting nvim. Could anyone please help me get this working and help ensure that the keymap is ported over to lua correctly? The latter is for my future configuration learning purposes.

Answer 1

First of all: Welcome to your (neo-)vim adventure and welcome to vi.stackexchange!

The problem

The problem here is, that this code:

getline('.')[col('.')-1] =~? '[]>)}]' || getline('.')[col('.')-1] =~? '[''"`]' && synIDattr(synID(line("."), col(".")+1, 1), "name") !~? 'string'

is actually vimscript and not lua! Sadly I'd just rewrite that into lua but that would take probably some time (for me)... take a look into my alternative section below. But if I remember correctly, you can execute vimscript by wrapping the vimscript code within [[ and ]] like this:

vim.keymap.set("n", "a", [[echo 'hello']], {})

this inserts hello into my text, but I can't explain you why, sadly. I rather expected to see it in the messages (see :h messages) but I guess that neovim takes the output of the vimscript part as an input to insert it into the given file.

Alternative

There's tabout.nvim which does exactly that what you're trying to do :) Maybe you want to give it a try.

EDIT 1

The reason why you get 1 if you just wrap the whole vimscript code with [[ and ]] is that it gets evaluated as vimscript code and if you look into the vimscript code, you can see that there are logical and's (&&) and logical or's (||).

I tried to adjust it into a mix of lua and vimscript but I couldn't get the cursor movement working:

vim.keymap.set("i", "a", function()
    local vimscript_code = [[getline('.')[col('.')-1] =~? '[]>)}]' || getline('.')[col('.')-1] =~? '[''"`]' && synIDattr(synID(line("."), col(".")+1, 1), "name") !~? 'string' ]]

    if vim.api.nvim_eval(vimscript_code) == 1 then
        -- add the cursor movement here
    end
end, {})

but I think the easiest solution would be, if you just write that part in vimscript if you really want to have this mapping:

vim.api.nvim_eval([[inoremap <expr> <Tab> getline('.')[col('.')-1] =~? '[]>)}]' || getline('.')[col('.')-1] =~? '[''"`]' && synIDattr(synID(line("."), col(".")+1, 1), "name") !~? 'string' ? '<Right>' : '<Tab>']])

But be aware that this only works, if your cursor is in front of the ending bracket (or ending " and ')!