Highlighting a search capture group

Question

By :set hl, the search result of a / expression is highlighted, for example:

And if one wants to replace one substring distinguished by its surrounding, one can do so elegantly using regex capture groups:

However, the search highlight does not reflect this capture group. Sometimes, it would be very helpful if it did, so you can feel more confident about your attempted regex. Does Vim have such a feature?

Answer 1

I think the quick answer is "no".

Partial solution: with a little extra typing, you can control what part of your search term gets hilighted: \zs to mark the start of highlighting, and \ze to mark the end.

This works nicely for searches:

/"\zs\(foo\|bar\)\ze"

But breaks search-and-replace, eg with:

:%s/"\zs\(foo\|bar\)\ze"/'\1'/gc

because it only replaces the highlighted part.

I've tested on this text:

"foo", "bar", "ba'z", 'foo', 'bar'

Answer 2

This command GL meant to run python on a matched group. In this case, we run a search on the matched pattern.

if has('python3')
    command! -nargs=* -range PY <line1>,<line2>python3 <args>
elseif has('python')
    command! -nargs=* -range PY <line1>,<line2>python <args>
endif 

function! RunPython2(match,run)
PY << EOF
import vim
try:
    match=vim.eval("a:match")
    retval=eval(vim.eval("a:run"),globals())
except Exception as e:
    import traceback
    exp=traceback.format_exc()
    retval=None
    try:
        vim.command("echom \"" + str(exp).replace("\"","\\\"") + "\"")
    except:
        pass

if retval==None: retval=match
vim.command("let retInVim=\"" + str(retval).replace("\"","\\\"") + "\"")
EOF
return retInVim
endfunction

function! RunPython(match,run)
PY << EOF
import vim
try:
    match=vim.eval("a:match")
    vim.command(' exec "PY " . a:run')
except Exception as e:
    import traceback
    exp=traceback.format_exc()
    try:
        vim.command("echom \"" + str(exp).replace("\"","\\\"") + "\"")
    except:
        pass
EOF
return ""
endfunction

function! GL(arg) range
    let lst=matchlist(a:arg,'/\(.\{-\}\)/\(.\{-}\) \(.*\)$')
    if lst[2]==#"rpy"
        exec a:firstline. "," . a:lastline . ":s\/" . lst[1] . "/\\=RunPython2(submatch(1),\"". escape(lst[3],"\"//") . "\")"
    elseif lst[2]==#"py"
        exec a:firstline. "," . a:lastline . ":s\/" . lst[1] . "/\\=submatch(0) . RunPython(submatch(1),\"". escape(lst[3],"\"//") . "\")"
    endif
endfunction

command! -nargs=1 -range GL <line1>,<line2>call GL(<f-args>)

To execute:

:%GL/pattern/py vim.command('call feedkeys("/'+match+'\\<CR>")')

Be aware of some nasty escaping in the match.

It assume only one pattern found to be highlighted (or it will highlight the last one).