Mappings with <expr> evaluated too early

[mikehaertl]

Environment:

• OS: Linux Mint
• (Neo)Vim version: NVIM v0.5.0-dev+1354-ga282a177d
• vim-which-key version: da2934f
• Have you reproduced with a minimal vimrc: yes

Describe the bug

I want to use a <expr> mapping like this:

`" r: ripgrep
nnoremap <expr> <leader>rg ":Rg " . input('rg search pattern: ') . "\<ESC>"

When I hit <leader>rg it will ask me for a search pattern and then execute :Rg mypattern.

If I only press <leader> and wait it should bring up the which-key menu as usual. But instead it prompts me fo the search pattern now:

<leader>
rg search pattern:

To Reproduce

Here the relevant parts from my config

let g:which_key_map = {}
let g:which_key_map.r = {
    \ 'name' : '+ripgrep',
    \ 'g' : 'grep'
  \}
call which_key#register(',', "g:which_key_map")

let mapleader = ","             " Map <leader> to , instead of default \
nnoremap <silent> <leader> :WhichKey ','<CR>
" r: ripgrep
nnoremap <expr> <leader>rg ":Rg " . input('rg pattern: ') . "\<ESC>"

Expected behavior

When hitting <leader> it should show the which-key menu.

Additional context

This is related to #60 and the fix in 80a1e88.

It seems like the plugin now evaluates all {rhs} of type <expr> when :WhichKey is invoked. But that's a problem if the expression must not be executed before the actual keys are used.

Actually the whole point of using expressions is probably to do some calculation on runtime. So I think the fix should be reverted / improved.

[TsukiGva2]

same problem here