Vim9 Script Ecosystem & AI Integration

The maturity of Vim9 script's modern constructs is now being leveraged by advanced AI development tools. Contributor Yegappan Lakshmanan recently demonstrated the efficacy of these new features through two projects generated using GitHub Copilot:

• Battleship in Vim9: A complete implementation of the classic game, showcasing classes and type aliases. [GitHub]
• Number Puzzle: A logic game demonstrating the efficiency of modern Vim9 for interactive plugins. [GitHub]

1. Auto-completion

Vim's standard completion frequently checks for user input while searching for new matches. It is responsive irrespective of file size. This makes it well-suited for smooth auto-completion.

vim9script
def InsComplete()
    if getcharstr(1) == '' && getline('.')->strpart(0, col('.') - 1) =~ '\k$'
        SkipTextChangedIEvent()
        feedkeys("\<c-n>", "n")
    endif
enddef

def SkipTextChangedIEvent(): string
    # Suppress next event caused by <c-e> (or <c-n> when no matches found)
    set eventignore+=TextChangedI
    timer_start(1, (_) => {
        set eventignore-=TextChangedI
    })
    return ''
enddef

set cot=menuone,popup,noselect inf

autocmd TextChangedI * InsComplete()

inoremap <silent> <c-e> <c-r>=<SID>SkipTextChangedIEvent()<cr><c-e>

2. Live grep, fuzzy find file, fuzzy find buffer

vim9script

var selected_match = null_string
var allfiles: list<string>

def GrepComplete(arglead: string, cmdline: string, cursorpos: number): list<any>
    return arglead->len() > 1 ? systemlist($'grep -REIHns "{arglead}"' ..
       ' --exclude-dir=.git --exclude=".*" --exclude="tags" --exclude="*.swp"') : []
enddef

def VisitFile()
    if (selected_match != null_string)
        var qfitem = getqflist({lines: [selected_match]}).items[0]
        if qfitem->has_key('bufnr') && qfitem.lnum > 0
            var pos = qfitem.vcol > 0 ? 'setcharpos' : 'setpos'
            exec $':b +call\ {pos}(".",\ [0,\ {qfitem.lnum},\ {qfitem.col},\ 0]) {qfitem.bufnr}'
            setbufvar(qfitem.bufnr, '&buflisted', 1)
        endif
    endif
enddef

def FuzzyFind(arglead: string, _: string, _: number): list<string>
    if allfiles == null_list
        allfiles = systemlist($'find {get(g:, "fzfind_root", ".")} \!
                   \( -path "*/.git" -prune -o -name "*.swp" \) -type f -follow')
    endif
    return arglead == '' ? allfiles : allfiles->matchfuzzy(arglead)
enddef

def FuzzyBuffer(arglead: string, _: string, _: number): list<string>
    var bufs = execute('buffers', 'silent!')->split("\n")
    var altbuf = bufs->indexof((_, v) => v =~ '^\s*\d\+\s\+#')
    if altbuf != -1
        [bufs[0], bufs[altbuf]] = [bufs[altbuf], bufs[0]]
    endif
    return arglead == '' ? bufs : bufs->matchfuzzy(arglead)
enddef

def SelectItem()
    selected_match = ''
    if getcmdline() =~ '^\s*\%(Grep\|Find\|Buffer\)\s'
        var info = cmdcomplete_info()
        if info != {} && info.pum_visible && !info.matches->empty()
            selected_match = info.selected != -1 ? info.matches[info.selected] : info.matches[0]
            setcmdline(info.cmdline_orig) # Preserve search pattern in history
        endif
    endif
enddef

command! -nargs=+ -complete=customlist,GrepComplete Grep VisitFile()
command! -nargs=* -complete=customlist,FuzzyBuffer Buffer exe 'b ' .. selected_match->matchstr('\d\+')
command! -nargs=* -complete=customlist,FuzzyFind Find exe !empty(selected_match) ? $'e {selected_match}' : ''

nnoremap <leader>g :Grep<space>
nnoremap <leader>G :Grep <c-r>=expand("<cword>")<cr>

nnoremap <leader><space> :<c-r>=execute('let fzfind_root="."')\|''<cr>Find<space><c-@>
nnoremap <leader>fv :<c-r>=execute('let fzfind_root="$HOME/.vim"')\|''<cr>Find<space><c-@>
nnoremap <leader>fV :<c-r>=execute('let fzfind_root="$VIMRUNTIME"')\|''<cr>Find<space><c-@>
nnoremap <leader><bs> :Buffer <c-@>

autocmd CmdlineEnter : allfiles = null_list
autocmd CmdlineLeavePre : SelectItem()

3. Auto Completion

vim9script

def CmdComplete()
    var [cmdline, curpos] = [getcmdline(), getcmdpos()]
    if getchar(1, {number: true}) == 0  # Typehead is empty
            && !pumvisible() && curpos == cmdline->len() + 1
            && cmdline =~ '\%(\w\|[*/:.-]\)$' && cmdline !~ '^\d\+$'
        feedkeys("\<C-@>", "ti")
        SkipCmdlineChanged()
        timer_start(0, (_) => getcmdline()->substitute('\%x00', '', 'g')->setcmdline())
    endif
enddef

def SkipCmdlineChanged(key = ''): string
    set ei+=CmdlineChanged
    timer_start(0, (_) => execute('set ei-=CmdlineChanged'))
    return key != '' ? ((pumvisible() ? "\<c-e>" : '') .. key) : ''
enddef

set wim=noselect:lastused,full wop=pum wcm=<C-@> wmnu

autocmd CmdlineChanged : CmdComplete()
autocmd CmdlineEnter : set bo+=error
autocmd CmdlineLeave : set bo-=error

cnoremap <expr> <up> SkipCmdlineChanged("\<up>")
cnoremap <expr> <down> SkipCmdlineChanged("\<down>")

Optional: Autocompletion (Popup Menu)

For automatic popup menu completion as you type in search or : commands, include this in your .vimrc:

vim9script
def CmdComplete()
  var [cmdline, curpos, cmdmode] = [getcmdline(), getcmdpos(), expand('<afile>') == ':']
  var trigger_char = '\%(\w\|[*/:.-]\)$'
  var not_trigger_char = '^\%(\d\|,\|+\|-\)\+$'
  if getchar(1, {number: true}) == 0
      && !wildmenumode() && curpos == cmdline->len() + 1
      && (!cmdmode || (cmdline =~ trigger_char && cmdline !~ not_trigger_char))
    SkipCmdlineChanged()
    feedkeys("\<C-@>", "t")
    timer_start(0, (_) => getcmdline()->substitute('\%x00', '', 'ge')->setcmdline())
  endif
enddef

def SkipCmdlineChanged(key = ''): string
  set ei+=CmdlineChanged
  timer_start(0, (_) => execute('set ei-=CmdlineChanged'))
  return key == '' ? '' : ((wildmenumode() ? "\<C-E>" : '') .. key)
enddef

set wim=noselect:lastused,full wop=pum wcm=<C-@> wmnu

autocmd CmdlineChanged :,/,? CmdComplete()

# Optional: Preserve history recall behavior
cnoremap <expr> <Up> SkipCmdlineChanged("\<Up>")
cnoremap <expr> <Down> SkipCmdlineChanged("\<Down>")

# Optional: Customize popup height
autocmd CmdlineEnter : set bo+=error | exec $'set ph={max([10, winheight(0) - 4])}'
autocmd CmdlineEnter /,? set bo+=error ph=8
autocmd CmdlineLeave :,/,? set bo-=error ph&