Automatically add a closing " or ' when inserting one, but only if the cursor isn't inside a string already

Question

I've defined mappings in my vimrc to automatically enter close parentheses and braces when I enter opening ones with inoremap ( ()<esc>i.

I'd like to do the same for " and ', but only when the cursor currently isn't inside a string - as inside a string ' is probably an apostrophe rather than a string delimiter. How can I do this?

Answer 1

One approach might be to use syn* functions. Something like:

fun! Qtx(qt)
    let x = synIDattr(synIDtrans(synID(line("."), col("."), 1)), "name")
    if x != "String" && x != "Comment" && x != "Constant"
        return a:qt . a:qt
    endif
    return a:qt
endfun


inoremap <silent> <expr> ' Qtx("'")
inoremap <silent> <expr> " Qtx('"')

Idea is to take advantage of the syntax for buffer at cursor position. This can perhaps be solved better. But hopefully a start.

Answer 2

As it has been said, you'll have to check the syntax-context. The old lh-brackets API provides functions for that purpose: Map*Context() functions. Since then the brackets definitions has been encapsulated in :Bracket which will take the context (strings or comments) into consideration.

By default context aware mappings are defined for all the usual brackets pairs like this:

  :Brackets! ( )
  :Brackets! [ ] -visual=0
  :Brackets! [ ] -insert=0 -trigger=<leader>[

  :Brackets! " " -visual=0 -insert=1
  :Brackets! " " -visual=1 -insert=0 -trigger=""
  :Brackets! ' ' -visual=0 -insert=1 -but=function('lh#ft#is_text')
  :Brackets! ' ' -visual=1 -insert=0 -trigger=''

  :Brackets! < > -visual=1 -insert=0 -trigger=<localleader><

  :Brackets! { }
  :Brackets! { } -visual=1 -insert=0 -nl -trigger=<leader>{