Vim: Replace visual selection without overwriting the unnamed register

Question

How do I replace a visual selection with some register content without overwriting the unnamed ("") register by the visual selection?

The question

https://stackoverflow.com/questions/3837772/vim-replace-selection-with-default-buffer-without-overwriting-the-buffer

is basically the same, however the answer xnoremap p "_dP provided there doesn't work properly if applied to a selection that includes the last character of the line (not even the end of line character $). Furthermore, with this solution, the paste register is hardcoded (to the unnamed one).

I found a partial solution using c, namely "_c<C-R>"<Esc>. This still has the problem that the paste register is hard coded. Furthermore, I don't know how to use this in a vimscript function.

(My main goal is to write a command that takes a motion and then replaces everything between the current cursor position to the motion target by a given register. I currently have this:

noremap s :set opfunc=SensibleSubstitute<CR>g@
function! SensibleSubstitute(type)
    normal `[v`]
    normal "_c<C-R>"
endfunction

but the <C-R>" is not recognized and just inserted verbally. Furthermore I don't know how to use the selected register if the user for example types "asiw)

(PS: the accepted answer here has the same problems with selections at the end of hte line)

Answer 1

There are a lot of weird workarounds, but I do have an answer.

but the <C-R>" is not recognized and just inserted verbally.

If you want ctrl-r, you'll need "\<C-r>". (Note: Specifically with double quotes, not single. Try :echo "\<C-r>" and :echo '\<C-r>') Which unfortunately means you'll need the whole thing to be a rather convoluted exec command:

exec 'normal "_c'."\<C-r>".'"'

Furthermore I don't know how to use the selected register if the user for example types "asiw

You can get this in the v:register variable. Unfortunately, it's not quite that simple in your example. Try this for example:

noremap s :set opfunc=SensibleSubstitute<CR>g@
function! SensibleSubstitute(type)
  echo v:register
endfunction

Try something like "asiw. This always prints " instead of a. Why is that? Because of your remapping, you're effectively running

"a:set opfunc=SensibleSubstitute<CR>g@

When you really want to run

:set opfunc=SensibleSubstitute<CR>"ag@

So you'll have to use an <expr> mapping.

Putting this all together, this should work for you (though I haven't tested it a whole lot):

noremap <expr> s ":set opfunc=SensibleSubstitute\<CR>".'"'.v:register."g@"
function! SensibleSubstitute(type)
  normal `[v`]
  exec 'normal "_c'."\<C-r>".v:register
endfunction