case-sensitive * with ignorecase on

Question

I like the behavior of the 'smartcase' option, which lets searches I type in by hand be case-insensitive by default, case-sensitive when there are any capital letters. I also like the behavior of the 'noignorecase' option, which lets searches generated by the editor (as when hitting * or #) be case-sensitive by default.

Unfortunately, 'smartcase' only does its magic when 'ignorecase' is on, so now I have a conflict: I can either get the nice behavior for hand-generated searches or the nice behavior for machine-generated searches, but not both.

How I can I get both nice behaviors?

Answer 1

You can fix that for the * command by putting the following mapping in your ~/.vimrc.

nnoremap * <silent> *N:let @/.='\C'<CR>n

When you type *, the mapping first executes the normal * command, then jumps back to the original word (N), then appends \C to the search expression (:let @/.='\C'<CR>), which makes it case-sensitive, and finally jumps forward again (n).

A complete compendium of bindings which doesn't clobber jumps (using Vitor's trick from the comments) and supports both forward and backwards search looks like this:

nnoremap <silent>  * :let @/='\C\<' . expand('<cword>') . '\>'<CR>:let v:searchforward=1<CR>n
nnoremap <silent>  # :let @/='\C\<' . expand('<cword>') . '\>'<CR>:let v:searchforward=0<CR>n
nnoremap <silent> g* :let @/='\C'   . expand('<cword>')       <CR>:let v:searchforward=1<CR>n
nnoremap <silent> g# :let @/='\C'   . expand('<cword>')       <CR>:let v:searchforward=0<CR>n

Answer 2

Here's a version of garyjohn/Vitor's solution that is a closer match to *'s behaviour in a few ways.

Making it an expr map fixes two things:

• 'hlsearch' -- turns on highlight immediately instead of after next n
• counts -- 3* skips the first two results

And explicitly handle some others:

• # when in the middle of a word -- jump to previous match instead of start of current match
• empty strings -- error
• nonwords -- * on ) at end of line doesn't do wholeword

function! s:SearchCword(wholeword, direction) abort
    let query = expand('<cword>')
    if empty(query)
        echohl ErrorMsg
        echomsg "E348: No string under cursor"
        echohl None
        return ""
    endif
    " Doing * on a nonword character at end of line produces no word
    " characters so wholeword is invalid.
    if a:wholeword && query =~# '\w'
        let query = '\<'.. query ..'\>'
    endif
    let @/ = query ..'\C'
    let searchforward = a:direction ==# 'n'
    let suffix = ''
    if !searchforward
        " v:searchforward is reset after functions so it must be part of our
        " returned command instead.
        let suffix = ":let v:searchforward=0\<CR>"
    endif
    if searchforward || s:IsCursorAtStartOfWord(expand("<cword>"))
        return a:direction .. suffix
    endif
    return a:direction..a:direction .. suffix
endfunction
function! s:IsCursorAtStartOfWord(query) abort
    let index_in_word = match(getline('.'), '\%' . col('.') ..'c'.. a:query)
    return index_in_word > 0
endfunction
nnoremap <expr>  * <SID>SearchCword(1, "n")
nnoremap <expr>  # <SID>SearchCword(1, "N")
nnoremap <expr> g* <SID>SearchCword(0, "n")
nnoremap <expr> g# <SID>SearchCword(0, "N")

I've added SearchCword to vim-searchsavvy as searchsavvy#SearchCword(). It supports a few more options (like making * follow 'smartcase' rules instead of always case sensitive).