How to copy all non-alphanumeric characters at the begining of the line to the next line?

Question

I want to implement something similar to Org mode M-RET into neovim. In Org mode it creates new list item or heading depending on what line the point is on.

I'm thinking of a mapping in neovim that copies everything from the beginning of the current line until the first alphanumeric character of the line and puts it on a new line. For example, with cursor at the end, it would transform this:

* list item
    * inner list item

into this:

* list item
    * inner list item
    * 

I think it could be done with :s but i couldn't make it work (:s/(^[^\w]*)(.*)/\1\2\n\1) and it would replace the whole line, which is unnecessary.

Ideally it should work in insert mode and shouldn't rewrite any registers.

Answer 1

You could start with this:

function! NewBullet()
    let l = getline('.')
    let l = substitute(l, '\w.*$','', '')
    return "\n" . l
endfunction

inoremap <expr> <F1> NewBullet()

Map-expression calls the function and inserts the returned text. Here a newline and the prefix of the line.

See :help :map-expression.

Answer 2

:substitute Command

The problem with the command you tried is that you used \n where you needed to use \r. (See :help s/\r.)

I don't really share your aversion to substituting the entire line, but we'll avoid that too:

:s/\v^(\W*).*\zs/\r\1

Insert Mode Mapping

To use this from insert mode, you can include it in an insert mode mapping:

:inoremap <F1> <Esc>:s/\v^(\W*).*\zs/\r\1<CR>A

How It Works

• \v – using "very magic"
• ^ – the start of the line
• (\W*) – as many non-alphanumeric characters* as possible, grouped into a capture group.
• .* – as many characters as possible (i.e. the rest of the line)
• \zs – set the start of the match (and thus the start of the replacement) to here

The replacement:

• \r – A newline
• \1 – The captured group.

_{* \W is equivalent to [0-9A-Za-z_] which is close enough to "non-alphanumeric" for your purposes.}

Avoid :substitute Entirely

It's also possible just to use regular editing commands to perform this task:

:inoremap <F1> <Esc>0y/\w<CR>o<Esc>pA

To see how this works, just try typing out the commands in the mapping's rhs manually!