Substitute tabs for equivalent number of spaces

Question

N.B I use the word blank here due to lack of a better word. By blank I mean the remaining part of a tab that is visualized after the starting part. Please feel free to edit this question.

I know there are questions already answered about vim's indent with tabs and align with spaces. But those questions have answers that says it's not possible or possible with supertab plugin. And moreover, my question is a little bit specific.

Take this example,

function! Format_tabs() abort
>...let s = ''
>...let s .= repeat(' ', &ts)
>...let t = '>..>...hello there>>...hey'
>...echo substitute(t, '\v[^\t]+\zs\t+\ze', s, 'g')
endfunction

where all > are start of a tab and following . are the remaining blank part throughout the tabstop.

And my tabstop settings are all set to 4.

In the above function I'm trying to convert the tabs in the string that are not at the beginning of a line with equivalent number of spaces. At the beginning I thought, I could replace each tabs, that are not at the beginning, with &tabstop number of spaces. But it turns out due to some settings, that I'm not trying to change, the tabs show different amount of blanks to figure out the alignment. So I need to figure out how many spaces I need to substitute the tabs for. But I have no idea!

Any solution?

Answer 1

This seems to work:

function! ReplaceMiddleTabs() abort
    let s:linenum = line('.')
    let s:current_line = getline(s:linenum)
    let s:temp = Format_tabs(s:current_line)
    call setline(s:linenum, s:temp)
endfunction

function! Format_tabs(line) abort
    let s:tablen = &ts
    let s:start = match(a:line, '^\s\+\zs.\ze')

    let s:temp = a:line
    let s:control = 1
    while s:control > 0
        let s:next = match(s:temp, '\t', s:start + 1)
        if s:next > 0
            let s:mod = (s:next % s:tablen)
            if s:mod == 0
                let s:mod = 4
            endif
            let s:substlen = s:tablen - s:mod + 1

            let s:temp = s:temp[0:s:next - 1] . repeat(' ', s:substlen) . s:temp[s:next + 1:]
        else
            let s:control = 0
        endif
    endwhile

    return s:temp
endfunction

The trick here is to calculate how many visual spaces each tab fills. To test it, I've used this:

|...|...|...|...|...|...|...|...|...|...|...|
>...|...>...|...|...|...|...|...|...|...|...|
>...|...|>..|...|...|...|...|...|...|...|...|
>...|...|.>.|...|...|...|...|...|...|...|...|
>...|...|..>|...|...|...|...|...|...|...|...|
>...|...|...>...|...|...|...|...|...|...|...|
>...|...>...|...|>..>...>...>...>...|...|...|
>...|...|>..|...|.>.|.>.|.>.|.>.|...|...|...|
>...|...|.>.|...|..>|..>|..>|..>|...|...|...|
>...|...|..>|...|...>...>...|...>...|...|...|
>...|...|...>...|...|...>...|..>|.>.|>..|...|
|...|...|...|...|...|...|...|...|...|...|...|

:%s/>\.*/\t/g
:call ReplaceMiddleTabs()
:%s/\t/>###/g

|...|...|...|...|...|...|...|...|...|...|...|
>###|...    |...|...|...|...|...|...|...|...|
>###|...|   |...|...|...|...|...|...|...|...|
>###|...|.  |...|...|...|...|...|...|...|...|
>###|...|.. |...|...|...|...|...|...|...|...|
>###|...|...    |...|...|...|...|...|...|...|
>###|...    |...|                   |...|...|
>###|...|   |...|.  |.  |.  |.  |...|...|...|
>###|...|.  |...|.. |.. |.. |.. |...|...|...|
>###|...|.. |...|...        |...    |...|...|
>###|...|...    |...|...    |.. |.  |   |...|
|...|...|...|...|...|...|...|...|...|...|...|

But this is my first vimscript function, so look at it with a grain of salt.

Edited: use % (thanks, @Enan Ajmain)

Answer 2

Based on the docs for submatch(), I would use something like (untested)

function! Format_tabs() abort
  let t = '>..>...hello there>>...hey'
  echo substitute(t, '\v[^\t]+\zs\t+\ze', '\=repeat(" ", len(submatch(1)) * &tabstop)', 'g')
endfunction

---

For reference, the example in the docs is

:echo substitute(text, '\d\+', '\=submatch(0) + 1', '')

Answer 3

1st Method

Use this command to convert tabs to spaces except the tabs used for indentation over a range of lines:

com! -bar -range=% RemoveTabs call s:remove_tabs(<line1>,<line2>)
function! s:remove_tabs(line1, line2) abort
    let view = winsaveview()
    let mods = 'sil keepj keepp'
    let range = a:line1 . ',' . a:line2
    let pat = '\%(^\s*\)\@!\&\(.\)\t'
    let l:Rep = {-> submatch(1) . repeat(' ', strdisplaywidth("\t", col('.') == 1 ? 0 : virtcol('.') ))}
    let g = 0
    while search("\t", 'n') && g < 999
        exe mods . ' ' . range .'s/' . pat . '/\=l:Rep()/ge'
        let g += 1
    endwhile
    call winrestview(view)
endfunction

2nd Method

Use this function to bind your Tab to a function that inserts tabs for indentation and spaces for alignment:

function! SpecialTab() abort
    if (col('.') == 1) || (matchstr(getline('.'), '\%'.(col('.') - 1).'c.') =~ '\t')
        return "\<Tab>"
    else
        return repeat("\<Space>", (&tabstop - (virtcol('.') % &tabstop)) + 1)
    endif
endfunction
inoremap <Tab> <C-R>=SpecialTab()<CR>