mode() incorrectly reports current mode

[pierreganty]

Describe the bug
Mode incorrectly reported using mode().

To Reproduce
Detailed steps to reproduce the behavior:

1. Run vim -Nu NONE -S mwe.vim9 where mwe.vim9 is

vim9script
snoremap <expr> s- execute('g:mode = mode(1)')->slice(0, 0)
xnoremap <expr> X- execute('g:mode = mode(1)')->slice(0, 0)
noremap <expr> n- execute('g:mode = mode(1)')->slice(0, 0)
vnoremap <expr> v- execute('g:mode = mode(1)')->slice(0, 0)
feedkeys('n-', 'x')
assert_equal('n', g:mode)
feedkeys('ghs-', 'x')
assert_equal('s', g:mode)
feedkeys("\<C-g>X-", 'x')
assert_equal('s', g:mode)
echom v:errors

2. The last assert should fail because, after inputting <C-g> we left select mode to go to visual.
   Therefore the mode() invokation (via mapping X-) should return visual mode.
   Note that the X- (visual only) mapping seems to be triggered correctly though.

Expected behavior
The last assert of mwe.vim9 should fail.

Environment (please complete the following information):

• Vim version 8.2.2932
• OS: macOS 11.3.1
• Terminal: Terminal.app

[pierreganty]

@lacygoill I came up with the mwe following your help on my last issue report but I am not too confident about my vim9script skills.

[lacygoill]

Yes, it seems that mode() doesn't pick up the correct mode at the end:

vim9script

snoremap <expr> s- execute('g:mode = mode(1)')->slice(0, 0)
xnoremap <expr> X- execute('g:mode = mode(1)')->slice(0, 0)

feedkeys('ghs-', 'x')
assert_equal('s', g:mode)

feedkeys("\<C-g>X-", 'x')
assert_equal('v', g:mode)

echom v:errors

['command line..script ... line 10: Expected ''v'' but got ''s''']

[brammool]

At the second feedkeys() select mode is not active, it works OK when it first starts select mode with "gh".
The mapping results in an empty string, this is what causes select mode to end.
That is because it looks like there is something to read, but it ends up empty. vgetc() then returns Esc to get out.

[lacygoill]

At the second feedkeys() select mode is not active

Ah yes, the contents of g:mode is actually stale, which explains this:

vim9script

snoremap <expr> s- execute('g:mode = mode(1)')->slice(0, 0)
xnoremap <expr> X- execute('g:mode = mode(1)')->slice(0, 0)

feedkeys('ghs-', 'x')
assert_equal('s', g:mode)

unlet g:mode
feedkeys("\<C-g>X-", 'x')
assert_equal('v', g:mode)

echom v:errors

E121: Undefined variable: g:mode
E116: Invalid arguments for function assert_equal('v', g:mode)

it works OK when it first starts select mode with "gh".
The mapping results in an empty string, this is what causes select mode to end.

OK, so this explains what the OP observed. I guess it's working as intended.

[lacygoill]

To the OP, you can work around this issue by using the special keycode <Ignore>. That is, instead of writing this:

snoremap <expr> s- execute('g:mode = mode(1)')->slice(0, 0)

Write this:

snoremap <expr> s- execute('g:mode = mode(1)')->slice(0, 0) .. '<Ignore>'
                                                            ^-----------^

[pierreganty]

Thanks to both of you. This is very helpful.