Standard way to implement a :tselect-like menu?

Question

In the context of developing a plug-in, what is the most portable (various versions of vim, nvim, ...) and readable way to implement a "menu" similar to what :tselect gives i.e. that

• appears in the bottom and takes as much screen as necessary
• paginates the content if there are too many entries to fit on a single screen
• implements the commands to navigate the list
• enumerates and indexes the entries
• waits for an input for the selected entry (or defaults to cancelling)

This could be hacked together using a buffer, remapping, etc. but there must be a simpler way to do such a common thing.

Ideally, I would like to pass the structured data and receive back the selected index.

Answer 1

Perhaps, you want inputlist(). It does not provide the item numbers, but it's quite easy to add them manually:

" MyChoice({list} [, {prompt}])
" Lets user choose an item from {list}. Returns the selected item index or -1.
" If {prompt} is omitted the default prompt is used.
function! MyChoice(list, ...)
    let l:prompt = a:0 ? a:1 : "Input number:"
    let l:idx = inputlist(insert(map(copy(a:list), '(1 + v:key) . ". " . v:val'), l:prompt))
    if l:idx >= 1 && l:idx <= len(a:list)
        return l:idx - 1
    endif
    return -1
endfunction

" example usage
let choice = MyChoice(['foo', 'bar', 'baz'])