How to go back to previous indentation level in insert mode?

Question

Sometimes vim's smartindent does not pick the correct level of indentation for the next line once you hit enter and you'd like to go back to the indentation level of the previous line and just go from there. I know that you can hit ctrl-d a few times to achieve this but it would be more useful for a key that immediately goes to the indentation level of the line above.

Answer 1

I don't know if it's pure coincidence, but Alexey Radev has just published the prev_indent plugin, which provides an insert mode mapping and :PrevIndent command to move the current line to the previous indentation level.

Answer 2

If you can't be bothered to install a plugin for such a simple task (I couldn't), try this simple mapping:

:inoremap <C-D> <Esc>:call setline(".",substitute(getline(line(".")),'^\s*',matchstr(getline(line(".")-1),'^\s*'),''))<CR>I

Now CtrlD in insert mode will do the deed: indent the current line like the previous line.

This works best before you start typing on the new line, because it will reset the cursor to just past the indentation.