[vim/vim] Command line mode mapping to <down> not working with wildmenu. (#6045)

[Daniel Steinberg]

Describe the bug

The documentation for wildmenumode() provides an example to make <c-j> work like <down> in wildmode:

:cnoremap <expr> <C-j> wildmenumode() ? "\<Down>\<Tab>" : "\<c-j>"

After creating that mapping, using <c-j> when the wildmenu is shown results in ^I being appended to the command line command.

The following mapping—intended to highlight the issue as opposed to be useful on its own—also encounters the problem.

:cnoremap j <Down>

To Reproduce

Detailed steps to reproduce the behavior:

1. Run vim --clean
2. Create mapping: :cnoremap <expr> <C-j> wildmenumode() ? "\<Down>\<Tab>" : "\<c-j>"
3. Type :e / followed by <tab> to bring up the wildmenu for the root directory.
4. Press <C-j>, which should "work like <down>".
5. ^I is appended to the command (twice), as opposed to having the same behavior as pressing <down>.

Expected behavior

I was expecting a move into the selected subdirectory, which is what happens when pressing <down>.

Environment (please complete the following information):

• Vim version: 8.2.700
• OS: Ubuntu 19.10
• Terminal: GNOME Terminal 3.34.2

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[lacygoill]

Possible duplicate of: #4954

For a workaround, make sure that 'wildcharm' has the same value as 'wildchar' (whose default is <Tab>/9):

vim -Nu NONE +'set wildmenu wildcharm=9' +'cnoremap <expr> <C-j> wildmenumode() ? "\<Down>\<Tab>" : "\<c-j>"'
                            ^^^^^^^^^^^

[lacygoill]

Or use feedkeys() with the t flag:

vim -Nu NONE +'set wildmenu' +'cnoremap <expr> <C-j> wildmenumode() ? feedkeys("\<down>\<tab>", "t")[-1] : "\<c-j>"'
                                                                                                 ^

See also:

• https://groups.google.com/d/msg/vim_dev/xf5TRb4uR4Y/djk2dq2poaQJ
• https://stackoverflow.com/q/14842987/9780968

[Daniel Steinberg]

Thanks @lacygoill.

(the example mapping in the documentation for wildmenumode() maps <c-j> to <down><tab>, but it seems that <down> alone works as expected, and the extra <tab> causes selection of the second item).

[Daniel Steinberg]

Closed #6045.

[lacygoill]

Fixed by 8.2.2221.